subject:"TDD is BS\?"

On Sunday, 23 June 2013 at 18:24:05 UTC, Andrei Alexandrescu 
wrote:

On 6/23/13 11:04 AM, Dicebot wrote:
On Sunday, 23 June 2013 at 17:54:01 UTC, Andrei Alexandrescu 
wrote:

On 6/23/13 10:34 AM, Adam D. Ruppe wrote:
We should do what php does, it was very successful. I assume 
it's a

dynamic library.


And what reason behind this other than millions of lemmings 
can't be

wrong? This approach is disaster when it comes to high load.


Would separate processes work better under high load? Educate 
me.


Andrei


It is not about process vs dynamic library, it is about basic 
threaded architecture used in Apache. Every single network server 
that I know that cares about performance uses some sort of event 
model and avoids any context switches at all possible costs. It 
does not matter where request processing code is, only how it 
fits in bigger picture.


Actually, server software with most impressive performance I have 
seen so far was implemented as single barebone process with all 
network stack and event library embedded. Slightly similar idea 
was propsoed here - 
http://highscalability.com/blog/2013/5/13/the-secret-to-10-million-concurrent-connections-the-kernel-i.html 
(found via reddit)

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On Sunday, 23 June 2013 at 18:42:12 UTC, Adam D. Ruppe wrote:

On Sunday, 23 June 2013 at 18:02:04 UTC, Dicebot wrote:
I can see reasons for wanting to keep it behind reverse proxy 
like nginx, but Apache?


Generally, I don't trust random http servers connected to the 
open internet for correctness, stability, security, and logging.


Especially not my code, There's a lot of the http protocol I 
never implemented, and putting apache, nginx, IIS, whatever, 
I'm just using Apache here because Andrei mentioned it, out in 
front will filter some of that out before it gets to my app.


Yes, that is why I have said that understand reasoning to use 
somthing like nginx or lighttpd - it is better to work behind 
something that has proper implementation of HTTP protocol and 
focus on application needs. I am using nginx for this on my own 
and perfectly satisfied with it.


But using Apache is just throwing away most part of performance 
achived by your backend, for nothing. And creating security 
issues in case your app is run via Apache module is it typically 
runs from http user in such scenarios and using app-specific UNIX 
access policies becomes much harder.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

On Monday, 24 June 2013 at 02:39:30 UTC, Andrei Alexandrescu 
wrote:

On 6/23/13 11:51 AM, Adam D. Ruppe wrote:
I think it is just an accident of history that mod_php ever 
got used.
Classic cgi implementations were still slow enough (especially 
with an
interpreted language) that people wanted to try something 
else, but the
other world of options hadn't taken root yet either (I think 
mod_php
even slightly predates fastcgi's introduction), and continues 
to exist

just out of inertia.


OK so what's the way to go now? One process per request? Seems 
heavy to me seeing as most requests last very little.


Andrei


One process/thread per CPU core + async I/O.
FastCGI as simple alternative (it is similar to CGI but does not 
respawn process after processing request).

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-24 Thread deadalnix


On Monday, 24 June 2013 at 09:07:54 UTC, Dicebot wrote:
Actually, server software with most impressive performance I 
have seen so far was implemented as single barebone process 
with all network stack and event library embedded. Slightly 
similar idea was propsoed here - 
http://highscalability.com/blog/2013/5/13/the-secret-to-10-million-concurrent-connections-the-kernel-i.html 
(found via reddit)


BTW, this article is full of bullshit and hand wavy stuff. I 
wanted to write a article destroying it, but I then decided that 
I had other thing to do than loose my time :D

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On Monday, 24 June 2013 at 09:22:58 UTC, deadalnix wrote:
BTW, this article is full of bullshit and hand wavy stuff. I 
wanted to write a article destroying it, but I then decided 
that I had other thing to do than loose my time :D


Yeah, it has plenty of bullshit but core idea is the same as one 
in project I have been engaged in and I can't write article about 
latter because of NDA, so using this an alternative available in 
the internet ;)

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-24 Thread Adam D. Ruppe

On Monday, 24 June 2013 at 02:39:30 UTC, Andrei Alexandrescu 
wrote:
so what's the way to go now? One process per request? Seems 
heavy to me seeing as most requests last very little.


Performance wise, I've found heard very good things about async 
i/o (like vibe.d) and had very good experience with a process 
pool (on linux anyway, cgi.d's fastcgi and new 
embedded_httpd_processes do this, the latter hitting 6,000 
requests per second for hello world on my machine!). The process 
pool forks ahead of time, then they take connections as they 
become available. Basically it puts the concurrency in the 
kernel's hands, which does a good job.


The zip I linked to yesterday does a simple one thread per 
connection, multiple requests per connection model. Doesn't scale 
very well, but works well and with simplicity on light loads.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On 6/21/13 4:02 PM, Walter Bright wrote:

On 6/21/2013 3:35 PM, Andrei Alexandrescu wrote:

On 6/21/13 3:22 PM, Adam D. Ruppe wrote:

Just for laughs I just slapped together a strstr


Post it and I'll destroy it.


Can I play, too? Mine from the Digital Mars C library. Haven't looked at
it since 2001.
==

/*_ strstr.c */
/* Copyright (C) 1985-2001 by Digital Mars */
/* All Rights Reserved */
/* www.digitalmars.com */
/* Written by Walter Bright */

#include stdio.h
#include ctype.h
#include stddef.h
#include string.h
#include stdlib.h

#if 0 /* Smaller but slower under many circumstances. */
char *strstr(const char *s1,const char *s2)
{ size_t len2;
size_t len1;
char c2 = *s2;

len1 = strlen(s1);
len2 = strlen(s2);
if (!len2)
return (char *) s1;
while (len2 = len1)
{
if (c2 == *s1)
if (memcmp(s2,s1,len2) == 0)
return (char *) s1;
s1++;
len1--;
}
return NULL;
}
#else


I won't comment on the B-M implementation. This brute force 
implementation has the problem of calling strlen on both strings 
upfront, which is arguably unnecessary. Although it doesn't affect 
complexity, it is an inefficiency hard to recover from. (The tradeoff is 
that memcmp will help with that.)


Andrei

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On 6/22/13 12:28 PM, Adam D. Ruppe wrote:

On Saturday, 22 June 2013 at 16:38:31 UTC, Andrei Alexandrescu wrote:
Huh, even the shortest impl I can think of is about the same length:

inout(char)* mystrstr(inout(char)* haystack, const(char*) needle) {
assert(haystack !is null);

if(needle is null)
return haystack;

while(*haystack) {
auto h = haystack;
const(char)* n = needle;
while(*n == *h  *n  *h) {
h++;
n++;
}
if(*n == 0)
return haystack;
haystack++;
}

return null;
}


I like this a lot better because it is more straightforward.


Still buggy. The empty string must be a prefix of any string including 
the empty string.


I describe the canonical implementation of substring brute for string 
search as far as I see it 
http://www.serversidemagazine.com/news/10-questions-with-facebook-research-engineer-andrei-alexandrescu/.



Andrei

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

On Sunday, 23 June 2013 at 16:07:05 UTC, Andrei Alexandrescu
wrote:
Still buggy. The empty string must be a prefix of any string
including the empty string.

Huh. Well, that makes sense. Just change while to do while and
you've got that. Probably compiles to exactly the same code as
your implementation in the link at that point.

But this probably told you more about my methods than getting it
right the first time would have: I'll just slap something
together that's good enough for the test case(s) fed to it and
then change it if new stuff arises where it fails. One of the
nice things about software is you generally don't have to get it
right the first time since it is so easy to change.

This is TDD-lite isn't it! lol

http://www.serversidemagazine.com/news/10-questions-with-facebook-research-engineer-andrei-alexandrescu/.

I definitely remember reading that when you posted it a while ago
because I have code that does that ?d writeln(hello, world);
? laying around.

http://arsdnet.net/dcode/dhp.d

It works by just reading the file and translating everything
outside the ?d? into a giant writeln(string literal), pasting
in the D code, then compile+running it, inserting a bunch of
imports so it works.

dom.d now supports those kinds of tags, it could probably be even
nicer, especially with a D lexer so it doesn't think ? is the
same as ?. But as I'm sure I said then, this is a bad idea
anyway since mixing code and html data leads to ugliness, whether
the code is php or D.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On 6/23/13 9:21 AM, Adam D. Ruppe wrote:

http://arsdnet.net/dcode/dhp.d

It works by just reading the file and translating everything outside the
?d? into a giant writeln(string literal), pasting in the D code, then
compile+running it, inserting a bunch of imports so it works.

dom.d now supports those kinds of tags, it could probably be even nicer,
especially with a D lexer so it doesn't think ? is the same as ?.
But as I'm sure I said then, this is a bad idea anyway since mixing code
and html data leads to ugliness, whether the code is php or D.


Nice! (BTW:

foreach(ln; stdin.byLine) {
string line = ln.idup ~ \n;

is simpler written as

foreach(ln; stdin.byLine(KeepTerminator.yes)) {
string line = ln.idup;

.)

Would be awesome if an Apache extension would make it trivial to write 
Web pages in D.



Andrei

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

On Sunday, 23 June 2013 at 16:28:56 UTC, Andrei Alexandrescu 
wrote:

foreach(ln; stdin.byLine(KeepTerminator.yes)) {


Yeah.

Would be awesome if an Apache extension would make it trivial 
to write Web pages in D.


Just use cgi or fastcgi, both are really easy to configure on 
apache (often needing nothing more than copying your executable 
into /cgi-bin/, or adding three lines to ,htaccess), and being 
separate processes, if you crash them it is no big deal. No need 
to do set up a reverse proxy or get your system administrator to 
load strange new Apache modules.


Or if you are just playing, you can skip apache altogether and 
use a D http server, like my cgi.d and vibe.d both offer 
(vibe.d's scales way better but mine is simpler).



But I kinda want to play with this now with shared libraries just 
for something to do so maybe I will.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On 6/23/13 10:34 AM, Adam D. Ruppe wrote:

Just use cgi or fastcgi, both are really easy to configure on apache
(often needing nothing more than copying your executable into /cgi-bin/,
or adding three lines to ,htaccess), and being separate processes, if
you crash them it is no big deal. No need to do set up a reverse proxy
or get your system administrator to load strange new Apache modules.


We should do what php does, it was very successful. I assume it's a 
dynamic library.



Or if you are just playing, you can skip apache altogether and use a D
http server, like my cgi.d and vibe.d both offer (vibe.d's scales way
better but mine is simpler).


But I kinda want to play with this now with shared libraries just for
something to do so maybe I will.


Awesome!

The more I think of it the more I get to the conclusion I should migrate 
my own website (www.erdani.com) to a 100% D toolchain.



Andrei

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-23 Thread Dicebot


On Sunday, 23 June 2013 at 17:34:52 UTC, Adam D. Ruppe wrote:
Would be awesome if an Apache extension would make it trivial 
to write Web pages in D.


Just use cgi or fastcgi, both are really easy to configure on 
apache (often needing nothing more than copying your executable 
into /cgi-bin/, or adding three lines to ,htaccess), and being 
separate processes, if you crash them it is no big deal. No 
need to do set up a reverse proxy or get your system 
administrator to load strange new Apache modules.


Or if you are just playing, you can skip apache altogether and 
use a D http server, like my cgi.d and vibe.d both offer 
(vibe.d's scales way better but mine is simpler).


Actually vibe.d embedded HTTP outperforms Apache. With high 
concurrency - a lot. I can see reasons for wanting to keep it 
behind reverse proxy like nginx, but Apache? I dream of the day 
this freaking monstrosity dies together with web app 
infrastructure it has developed. Please, don't help it survive 
with D module support. :(

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-23 Thread Dicebot

On Sunday, 23 June 2013 at 17:54:01 UTC, Andrei Alexandrescu 
wrote:

On 6/23/13 10:34 AM, Adam D. Ruppe wrote:
We should do what php does, it was very successful. I assume 
it's a dynamic library.


And what reason behind this other than millions of lemmings 
can't be wrong? This approach is disaster when it comes to high 
load.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On 6/23/13 11:04 AM, Dicebot wrote:

On Sunday, 23 June 2013 at 17:54:01 UTC, Andrei Alexandrescu wrote:

On 6/23/13 10:34 AM, Adam D. Ruppe wrote:
We should do what php does, it was very successful. I assume it's a
dynamic library.


And what reason behind this other than millions of lemmings can't be
wrong? This approach is disaster when it comes to high load.


Would separate processes work better under high load? Educate me.

Andrei

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On Sunday, 23 June 2013 at 18:02:04 UTC, Dicebot wrote:
I can see reasons for wanting to keep it behind reverse proxy 
like nginx, but Apache?


Generally, I don't trust random http servers connected to the 
open internet for correctness, stability, security, and logging.


Especially not my code, There's a lot of the http protocol I 
never implemented, and putting apache, nginx, IIS, whatever, I'm 
just using Apache here because Andrei mentioned it, out in front 
will filter some of that out before it gets to my app.


And who knows what kinds of hidden bugs my code has, so having a 
tested and reliable server out there to revive my process if it 
dies is nice too.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

On Sunday, 23 June 2013 at 18:24:05 UTC, Andrei Alexandrescu 
wrote:
Would separate processes work better under high load? Educate 
me.


One nice thing is you can spread separate processes across 
several machines. Another advantage of *cgi|embedded_httpd is 
that it is portable to other web servers too, you can just drop 
it into a shop that uses nginx or Microsoft IIS and expect it to 
work, whereas an Apache module is generally apache only.


I think it is just an accident of history that mod_php ever got 
used. Classic cgi implementations were still slow enough 
(especially with an interpreted language) that people wanted to 
try something else, but the other world of options hadn't taken 
root yet either (I think mod_php even slightly predates fastcgi's 
introduction), and continues to exist just out of inertia.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

BTW I should mention, I wasn't actually trying to do an Apache 
module. I wanted to do a D server that watches the files for 
changes, then recompiles them as needed and reloads the resulting 
file as a shared lib.


I could just run the compiled executable too, cgi style, but here 
I was more interested in playing with shared libraries than just 
getting it to work.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

On Sunday, 23 June 2013 at 17:54:01 UTC, Andrei Alexandrescu 
wrote:

I assume it's a dynamic library.


PHP can work as fastcgi too.

But I kinda want to play with this now with shared libraries 
just for

something to do so maybe I will.


Awesome!


Eh, not so much. I started playing and got a thing saying 
Runtime.loadLibrary is not yet implemented on posix... so went to 
do it myself and got random segfaults, relating to the garbage 
collector (and yes, I tried Runtime.initialize).


I've never done a shared library plugin before so I could be 
doing something wrong, but it seems to me that druntime said it 
wasn't implemented yet for a reason, must still have some work to 
do there. Oh well, maybe I'll try again next release.

Re: TDD is BS?

2013-06-23 Thread Paulo Pinto


Am 20.06.2013 11:26, schrieb Jacob Carlborg:

On 2013-06-20 00:13, Paulo Pinto wrote:


The issue is not to test third party libraries, far from it.

The problem is that you cannot mock them, specially if you rely a lot on
non virtual methods or pure function calls. Or on framework code that
calls your code back, after certain events happened in the system.


I would only mock an external service that needs to be available online.
I don't mock third party code. That would be insane. There's no limit.
Should I mock the standard library?


No, but if your code calls something that ends up calling again other 
part of your code, you might need to mock it somehow.


Specially if it is a library that does some IO (network, disk) in the 
process and is full of static methods.


--
Paulo

Re: TDD is BS?

2013-06-23 Thread Jacob Carlborg


On 2013-06-23 21:50, Paulo Pinto wrote:


No, but if your code calls something that ends up calling again other
part of your code, you might need to mock it somehow.


I'm using same approach there. If I'm testing method a and it also 
calls method b. I assume method b works and I don't mock it. Then I 
make sure to have a test for method b as well. A given test only tests 
one method.



Specially if it is a library that does some IO (network, disk) in the
process and is full of static methods.


Especially network IO is a good idea to mock.

--
/Jacob Carlborg

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

On Sunday, 23 June 2013 at 17:54:01 UTC, Andrei Alexandrescu 
wrote:

Awesome!


I realized initializing the runtime might have been a mistake 
when loading the .so and moreover I was using the wrong calling 
convention. Fixed that and now the shared library thing works. On 
Linux at least, I hardcoded .so so don't try it anywhere else.


Here's some code:
http://arsdnet.net/dcode/dhp.zip

unzip it, hit make. dhp2.d is the main file here, it also uses 
some helper libraries you can see in the arsd folder.


Then run ./dhp2 in another window or something. It is a long 
running process that serves http.


Head over to your browser and surf to
http://localhost:8085/


It will take a couple seconds to load the first time, because it 
needs to compile the code. Subsequent loads will pull it from a 
cache and be faster.


Anyway it will show you some stuff and a link. These pull from 
the files in the zip called index.dhp and dhpt.dhp. index is just 
html, no D code, although it will compile it since this server 
compiles everything.



dhpt.dhp actually includes some D:

pHello, % cgi.write(cgi.request(name, user)); %, 
happy to see you./p


Note: you access that by going to localhost:8085/dhpt, NOT 
/dhpt.dhp. It strips out dots from the url as a way of sanitizing 
the filename so keep it simple.


It uses ASP style % % tags instead of ?d ? because my dom.d 
already understands them. (BTW this parses the .dhp files to be 
well-formed xml, so if you mismatch tags, it will throw. It might 
be fun to put the DOM node in scope to inspect too).


There's a Cgi cgi in scope in the function it builds here. Use it 
to do communication instead of writeln() etc., as seen in this 
example.




Here's where the shared library magic comes in: feel free to edit 
one of those .dhp files, or create your own, and go back to it in 
the browser. It will recompile and present it to you without 
having to restart the server. That's kinda cool. The downside is 
if you segfault in here it will take the whole server down so 
don't do that.


If you fail compiling though, it will actually read dmd's output 
and translate the filename and line number to match the .dhp file 
input, instead of the .d file dmd actually sees. So it feels less 
like a filthy hack then.


Feel free to look at index.d and dhpt.d in that same folder after 
you browse to them to see what the generated code looks like.





S yeah. I'll probably never use this, dom templates rok so 
much more than anything asp/php style, but if you wanna play, 
feel free and let me know if you want more features or see bugs. 
Probably won't be too hard to fix up now that it is started.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On 6/23/13 11:51 AM, Adam D. Ruppe wrote:

I think it is just an accident of history that mod_php ever got used.
Classic cgi implementations were still slow enough (especially with an
interpreted language) that people wanted to try something else, but the
other world of options hadn't taken root yet either (I think mod_php
even slightly predates fastcgi's introduction), and continues to exist
just out of inertia.


OK so what's the way to go now? One process per request? Seems heavy to 
me seeing as most requests last very little.


Andrei

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-23 Thread deadalnix

On Monday, 24 June 2013 at 02:39:30 UTC, Andrei Alexandrescu 
wrote:

On 6/23/13 11:51 AM, Adam D. Ruppe wrote:
I think it is just an accident of history that mod_php ever 
got used.
Classic cgi implementations were still slow enough (especially 
with an
interpreted language) that people wanted to try something 
else, but the
other world of options hadn't taken root yet either (I think 
mod_php
even slightly predates fastcgi's introduction), and continues 
to exist

just out of inertia.


OK so what's the way to go now? One process per request? Seems 
heavy to me seeing as most requests last very little.




That is what apache used to do when mod_php was introduced 
anyway. This whole conversation has gone out of control :D


mod_php was a way to reduce the communication overhead and avoid 
2 process per request in the first place (instead of one).


It become plain obvious that no silver bullet exists here. The 
solution seems to be a mix of fibers/threads and processes where 
number of each depends on your workload and the actual hardware 
it is running on. Most high performance and high scalability 
system are converging toward one flavor of that pattern.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-22 Thread deadalnix

On Friday, 21 June 2013 at 21:33:43 UTC, Andrei Alexandrescu 
wrote:
If there's any need to reach for documentation, the interviewer 
has failed. When interviewing we (at Facebook) ask problems 
that are likely to appear in a normal day's work, but for which 
the typical libraries don't help. (E.g. many libraries don't 
can't help with implementing unstable remove (see 
std.algorithm).)




Amongst other thing, I did a merge sort and a quicksort in my FB 
interviews. It is fair to assume they can be found as libraries. 
But overall the process is really accurate to assert what a dev 
can do. Most question were technically challenging, but weren't 
tricks or overly complicated and useless.


For the anecdote, my quicksort was buggy, but my interviewer 
convinced me it wasn't - when later check (after the interview) 
demonstrated is indeed was.


Also it's fair to ask about implementing a stdlib function 
itself if the interview concerns some systems-level work; e.g. 
brute-force strstr() is fair game and I think any engineer 
should be able to lift it off the ground quickly (to my dismay, 
only a fraction can). Paradoxically use of stdlib functions may 
actually hurt; I've seen people who e.g. call strlen() in a 
loop in order to implement strstr()!




When i was doing interview, I used to ask people to program a 
function that sort an array of integer. No constraint of 
performance or anything, the good old 5 lines bubble sort would 
have been accepted. Most can't.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On 2013-06-21 23:33, Andrei Alexandrescu wrote:


If there's any need to reach for documentation, the interviewer has
failed. When interviewing we (at Facebook) ask problems that are likely
to appear in a normal day's work, but for which the typical libraries
don't help. (E.g. many libraries don't can't help with implementing
unstable remove (see std.algorithm).)

Also it's fair to ask about implementing a stdlib function itself if the
interview concerns some systems-level work; e.g. brute-force strstr() is
fair game and I think any engineer should be able to lift it off the
ground quickly (to my dismay, only a fraction can). Paradoxically use of
stdlib functions may actually hurt; I've seen people who e.g. call
strlen() in a loop in order to implement strstr()!


Yes, if they tell you that from the beginning. Instead they said: 
solve it anyway you like, then they started to add restrictions.


--
/Jacob Carlborg

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On 2013-06-22 01:58, H. S. Teoh wrote:


And where's the unittest block? ;-)  (OK OK, I know this wasn't written
in D. But I had to ask. :-P)


DMC does support contracts, as an extension. That is, in and out 
contracts. I don't know about unit test blocks.


--
/Jacob Carlborg

Re: TDD is BS?


On 2013-06-22 00:12, Nick Sabalausky wrote:


- The nasty little details like pointer/memory problems, linker errors,
   etc that real people have to deal with are neatly glossed over and
   sidestepped.


They never teach you about that.


- There was one CS101 teacher (I had to tutor her unfortunate students)
   who constantly bragged about being from a real-world software
   company...but she was a Java-addict (circa v1.2-v1.4) who kept trying
   to teach OO *before* basic flow-of-execution. Consequently, none of
   her unfortunate students had the slightest clue what was going on.

- Many of the professors are terrible programmers themselves. For
   example, I had one who openly admitted the only language he knew was
   C, and yet at one point it became painfully obvious that he had
   almost no comprehension of null-terminated strings.


What annoys me is that sometimes they teach flat out lies to the students.

I watch a couple of videos from a course from Standford, I think it was 
algorithms and data structures or similar. The teacher introduce the Map 
data structure by showing an interface for it and how it works. She 
tells the student that you cannot have any other type for the keys than 
strings. I think she even says it's impossible. I can understand that 
they don't want to make it too complicated when it's introduced for the 
first time. But she at least could have said something like, for now, 
lets imagine only string types are possible.


--
/Jacob Carlborg

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-22 Thread Andrej Mitrovic

On 6/22/13, Walter Bright newshou...@digitalmars.com wrote:
 Can I play, too? Mine from the Digital Mars C library. Haven't looked at it

 #if 0 /* Smaller but slower under many circumstances. */
 char *strstr(const char *s1,const char *s2)
 {   size_t len2;
  size_t len1;
  char c2 = *s2;

  len1 = strlen(s1);
  len2 = strlen(s2);
  if (!len2)
   return (char *) s1;
  while (len2 = len1)
  {
   if (c2 == *s1)
   if (memcmp(s2,s1,len2) == 0)
   return (char *) s1;
   s1++;
   len1--;
  }
  return NULL;
 }

Some things i've noticed about this implementation:

- c2 is assigned by pointer dereference, but then strlen is called on
s2 and you may get an early exit, meaning c2 was not needed at this
point. I'd move c2 below the strlen call.

- The memcp doesn't have to compare len2 amount of chars if you've
already compared the first character, it can call memcmp(s2+1, s1+1,
len2-1). Although I'm not sure whether it's faster to do it this way
(maybe it is, if those variables are actually registers..).

And notes about both implementations:

- You're casting a const char * to a char * in the return, you should
instead provide an overload of strstr taking char* and returning
char*.

- You seem to have missed the most basic and most important check. You
didn't attempt to compare the memory address of both pointers against
each other before doing any other work. If they both point to the same
memory, the strings are guaranteed to be equal.

Re: TDD is BS?


On 2013-06-21 21:11, Walter Bright wrote:


I've been around long enough to have seen an endless parade of magic new
techniques du jour, most of which purport to remove the necessity of
thought about your programming problem.


One needs to be opened minded and be able to try new things.


But there is one technique that stands head and shoulders above the
others in improving code quality, sometimes dramatically so. That's unit
testing coupled with a coverage analyzer.


I can imagine that these techniques have been new at some point in time 
as well. It's possible that a new technique comes a long that help you 
as much as these techniques do.


--
/Jacob Carlborg

Re: TDD is BS?


On 2013-06-22 00:12, Nick Sabalausky wrote:


- There was one CS101 teacher (I had to tutor her unfortunate students)
   who constantly bragged about being from a real-world software
   company...but she was a Java-addict (circa v1.2-v1.4) who kept trying
   to teach OO *before* basic flow-of-execution. Consequently, none of
   her unfortunate students had the slightest clue what was going on.


We learned OO before any programming. First we had a course about 
analyze and design of object oriented systems, or something like that. 
They thought the basic concepts of OO, UML diagrams and other stuff. 
After that course we learned programming and the practical side of OO, 
that is Java.



- Many of the teachers don't even teach, they just collect the
   thousands of dollars in tuition and give you a book recommendation
   (really more of a demand than a recommendation). Now, I'm a strong
   believer in being self-taught and learning from books, but all I need
   for that is a library card, not a $100k debt and four years of elitist
   attitudes from people who clearly don't know what they're doing
   anyway.


During my years at the university I bought three books. One of the was 
really good, the rest wasn't worth it.


--
/Jacob Carlborg

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-22 Thread Andrej Mitrovic

On 6/22/13, Adam D. Ruppe destructiona...@gmail.com wrote:
 On Saturday, 22 June 2013 at 11:01:53 UTC, Andrej Mitrovic wrote:
 - You're casting a const char * to a char * in the return, you
 should instead provide an overload of strstr taking char* and
 returning char*.

 I'm pretty sure the C standard says to do it with the const arg
 but mutable return.

 http://en.cppreference.com/w/c/string/byte/strstr


Ah, I momentarily forgot C doesn't have overloading, which is probably
where Walter's function was implemented in. In C++ there are overloads
of this function:

http://www.cplusplus.com/reference/cstring/strstr/

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-22 Thread Jérôme M. Berger

Adam D. Ruppe wrote:
 On Friday, 21 June 2013 at 22:35:55 UTC, Andrei Alexandrescu 
 wrote:
 Post it and I'll destroy it.
 
 
 inout(char)* mystrstr(inout(char)* haystack, const(char*) needle) 
 {
  assert(haystack !is null);
 
  if(needle is null)
  return haystack;
 
  const(char)* where = needle;
  inout(char)* gotit;
 
  while(*haystack) {
  if(*haystack == *where) {
  if(gotit is null)
  gotit = haystack; // store where the match started
  where++;
  haystack++;
  if(*where == 0)
  return gotit;
  } else {
  // if we were in the middle of a match, we'll want to
  // check the current character again so only advance 
 if
  // we're at the beginning
  if(gotit is null)
  haystack++;
  else {
  // partial match, but not complete so no good
  // start over, including the current *haystack
  where = needle;
  gotit = null;
  }
  }
  }
 
  return null;
 }
 
I haven't tried running it, but this looks to me like it won't find
ababc in abababc...

Jerome
-- 
mailto:jeber...@free.fr
http://jeberger.free.fr
Jabber: jeber...@jabber.fr



signature.asc
Description: OpenPGP digital signature

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-22 Thread Adam D. Ruppe


On Saturday, 22 June 2013 at 13:55:26 UTC, Jérôme M. Berger wrote:
	I haven't tried running it, but this looks to me like it won't 
find ababc in abababc...



You're right. I should have went backwards all the way, not just 
in the one case.


This passes all the tests:

inout(char)* mystrstr(inout(char)* haystack, const(char*) needle) 
{

assert(haystack !is null);

if(needle is null)
return haystack;

const(char)* where = needle;
inout(char)* gotit;

while(*haystack) {
if(*haystack == *where) {
if(gotit is null)
gotit = haystack;
where++;
if(*where == 0)
return gotit;
} else {
haystack -= where - needle;
where = needle;
gotit = null;
}

haystack++;
}

return null;
}

Re: TDD is BS?

2013-06-22 Thread QAston


On Friday, 21 June 2013 at 16:49:26 UTC, H. S. Teoh wrote:

On Fri, Jun 21, 2013 at 05:48:25PM +0200, Jacob Carlborg wrote:

On 2013-06-21 16:56, H. S. Teoh wrote:

+1, me too! I can say that 85-90% of what I do at work today, 
I
learned from my personal coding projects, not from the CS 
courses I
took in university. (That's why I like to joke about CS grads 
knowing

more about uncomputable problems than computable ones...)

It feels like there's something wrong with the world here :)

[...]

Only something wrong? ;-)

To be fair, though, I can understand why university programs 
are that
way: their goal is to produce more researchers and professors 
who may
join the faculty and produce more research. So they focus more 
on the

theoretical aspects of computer science in order to produce such
candidates, whereas focusing on more practical aspects is 
something for

technical colleges whose goal is to produce industry workers.

Unfortunately, in North America at least, the technical 
colleges lean
more toward stuff like how to use MS Word, how to organize 
your

company data in MS SQL, rather than _real_ programming, and
universities that actually *teach* real programming are more 
interested
in finding solutions to uncomputable problems than teaching 
students how
to solve computable ones, so there's a gap in the area of 
producing
qualified industry coders who can write functional software. 
There *are*
pockets of competent programming education here and there, of 
course,

but this is the impression I get from the general situation.


T


Yay, a uni bashing thread. I'm a student and I like it, so here's 
some subjective opinion.


I don't know how it's in USA, but where i live we have 2 
possibilities of getting CS education at uni level: a course at 
pure university and a course at something we call university 
of technology. Basically the former focuses much more on 
academic problems, the latter grants you with engineer title 
with all that implies - you learn how computers work from 
electrical level up to the high abstractions of disciplines like 
AI or image processing.


I've been interested in programming long before I went to the 
university of technology. I went there to expand my knowledge 
on the topic. It worked out great for me, because unlike in our 
highschool I didn't have to learn stuff unrelated to my 
interests. I've learned a lot and met some very skillful people. 
Many of them bash unis just like you guys, yet they still gained 
many skills there - but that's typical - I've heard a lot of 
whining during my entire education.


I want to point out that having a CS course alone doesn't make 
you a good coder. First - because CS is not only about coding, 
that's a wide discipline. Second - your attitude is what really 
matters. Noone's going to make you a (very)good C programmer in 
90h course - you just get enough to grasp important concepts to 
be able to easily expand on your own in areas you like. If you 
don't like CS, yet you finish the course, you've lost X years of 
life for getting a sheet of paper and some opportunity to get a 
job which you probably won't like or won't be good at. Third - 
unis are really not about producing enterprise workers, you don't 
need much knowledge to write apps which throw around data between 
crud app and db. Instead they give you ability to use common 
scientific methodology, a complete overview of CS, means to study 
(or even push forward) the discipline you're interested in and 
most important, they teach how stupid everyone (especially you - 
that's a painfull lesson) really is.


I'm not saying that you can't get all of this on your own, yet 
it's easier that way. I was a self taught programmer, but I feel 
that my knowledge is more complete now (and some of the knowledge 
is very important for a systems programmer). It's obviously the 
same other way around - you can pass all the exams and get 
nothing from that. It's up to you what you're going to do with 
free time. Important note: public unis are free in my country, I 
probably wouldn't study otherwise.

Re: TDD is BS?

2013-06-22 Thread Andrei Alexandrescu


On 6/22/13 3:18 AM, Jacob Carlborg wrote:

I watch a couple of videos from a course from Standford, I think it was
algorithms and data structures or similar. The teacher introduce the Map
data structure by showing an interface for it and how it works. She
tells the student that you cannot have any other type for the keys than
strings.


I'm very surprised to hear that, Stanford is a good university. You'd 
certainly need good evidence to make us believe that :o).


Andrei

Re: TDD is BS?

2013-06-22 Thread Andrei Alexandrescu


On 6/22/13 5:54 AM, Jacob Carlborg wrote:

On 2013-06-21 21:11, Walter Bright wrote:


I've been around long enough to have seen an endless parade of magic new
techniques du jour, most of which purport to remove the necessity of
thought about your programming problem.


One needs to be opened minded and be able to try new things.


But there is one technique that stands head and shoulders above the
others in improving code quality, sometimes dramatically so. That's unit
testing coupled with a coverage analyzer.


I can imagine that these techniques have been new at some point in time
as well. It's possible that a new technique comes a long that help you
as much as these techniques do.


Was new in 1962: http://www.dtic.mil/dtic/tr/fulltext/u2/282767.pdf.

Andrei

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-22 Thread Andrei Alexandrescu


On 6/22/13 7:10 AM, Adam D. Ruppe wrote:

On Saturday, 22 June 2013 at 13:55:26 UTC, Jérôme M. Berger wrote:

I haven't tried running it, but this looks to me like it won't find
ababc in abababc...



You're right. I should have went backwards all the way, not just in the
one case.

This passes all the tests:


It's still buggy. Overly complicated, too - at 21 lines, it's about 
twice as large as the canonical implementation.


Andrei

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-22 Thread Walter Bright


On 6/22/2013 4:01 AM, Andrej Mitrovic wrote:

On 6/22/13, Walter Bright newshou...@digitalmars.com wrote:

Can I play, too? Mine from the Digital Mars C library. Haven't looked at it

#if 0 /* Smaller but slower under many circumstances. */
char *strstr(const char *s1,const char *s2)
{   size_t len2;
  size_t len1;
  char c2 = *s2;

  len1 = strlen(s1);
  len2 = strlen(s2);
  if (!len2)
return (char *) s1;
  while (len2 = len1)
  {
if (c2 == *s1)
if (memcmp(s2,s1,len2) == 0)
return (char *) s1;
s1++;
len1--;
  }
  return NULL;
}


Some things i've noticed about this implementation:


It's wrapped in #if 0 ... #endif ? :-)


- c2 is assigned by pointer dereference, but then strlen is called on
s2 and you may get an early exit, meaning c2 was not needed at this
point. I'd move c2 below the strlen call.


Yup.


- The memcp doesn't have to compare len2 amount of chars if you've
already compared the first character, it can call memcmp(s2+1, s1+1,
len2-1). Although I'm not sure whether it's faster to do it this way
(maybe it is, if those variables are actually registers..).


Yup.


And notes about both implementations:

- You're casting a const char * to a char * in the return, you should
instead provide an overload of strstr taking char* and returning
char*.


The function bodies would be identical - why have two of them?


- You seem to have missed the most basic and most important check. You
didn't attempt to compare the memory address of both pointers against
each other before doing any other work. If they both point to the same
memory, the strings are guaranteed to be equal.


Most important? I've never even run across this case.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-22 Thread Peter Alexander

On Friday, 21 June 2013 at 21:33:43 UTC, Andrei Alexandrescu 
wrote:
Also it's fair to ask about implementing a stdlib function 
itself if the interview concerns some systems-level work; e.g. 
brute-force strstr() is fair game and I think any engineer 
should be able to lift it off the ground quickly (to my dismay, 
only a fraction can). Paradoxically use of stdlib functions may 
actually hurt; I've seen people who e.g. call strlen() in a 
loop in order to implement strstr()!


I think it's fair game whatever kind of work you are doing. The 
tests aren't so much about the algorithm, but showing that the 
candidate thinks about edge cases, interfaces, possible failure 
cases etc.  These are things you need to think about even if your 
job is just to essentially glue libraries together. Simple tasks 
like strstr just provide a nice small task that test these things.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-22 Thread Andrej Mitrovic

On 6/22/13, Walter Bright newshou...@digitalmars.com wrote:
 It's wrapped in #if 0 ... #endif ? :-)

Hehe. I should totally use that as an argument in a future interview.
I'll wrap all my coding-answers in '#if 0', and if they're wrong I'll
just say oh, but this code doesn't *actually* exist!. :p

 The function bodies would be identical - why have two of them?

Yeah nevermind, it's C, I was thinking about C++. Then again D would
blow them both out the water since it has inout.

 Most important? I've never even run across this case.

Ok, maybe not that important. It's likely a rare case.

Btw, does anyone know if the typical memcmp implementation tries to
compare the pointers' addresses first to see if they match?

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-22 Thread Adam D. Ruppe

On Saturday, 22 June 2013 at 16:38:31 UTC, Andrei Alexandrescu 
wrote:

It's still buggy.


What's the test case? I also forgot the empty string, blargh. 
Let's scrap it.


Overly complicated, too - at 21 lines, it's about twice as 
large as the canonical implementation.


Huh, even the shortest impl I can think of is about the same 
length:


inout(char)* mystrstr(inout(char)* haystack, const(char*) needle) 
{

assert(haystack !is null);

if(needle is null)
return haystack;

while(*haystack) {
auto h = haystack;
const(char)* n = needle;
while(*n == *h  *n  *h) {
h++;
n++;
}
if(*n == 0)
return haystack;
haystack++;
}

return null;
}


I like this a lot better because it is more straightforward. My 
first draft was trying to avoid looking at the same character 
twice, but obviously that didn't work so fixing that ended up 
doing the same thing as this anyway. I guess better to KISS than 
be embarrassingly wrong, eh?



You could do it in about ten lines like this:

inout(char)* mystrstr(inout(char)* haystack, const(char*) needle) 
{

while(*haystack) {
auto h = haystack;
const(char)* n = needle;
while(*n == *h  *n  *h)
h++, n++; // LOL COMMA OPERATOR
if(*n == 0)
return haystack;
haystack++;
}
return null;
}


But I really like the null check. Yes, I know the hardware does 
it, but it is a pain in the butt to fire up a debugger when a 
null hits you in the middle of something. The nice assertion 
failure message is so much faster to handle.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-22 Thread Walter Bright


On 6/22/2013 12:12 PM, Andrej Mitrovic wrote:

Most important? I've never even run across this case.


Ok, maybe not that important. It's likely a rare case.

Btw, does anyone know if the typical memcmp implementation tries to
compare the pointers' addresses first to see if they match?


I don't know about typical, but I've never seen one that did.

Re: TDD is BS?


On 2013-06-22 18:27, Andrei Alexandrescu wrote:


I'm very surprised to hear that, Stanford is a good university. You'd
certainly need good evidence to make us believe that :o).


I was surprised when I watch the video. But here it is:

https://itunes.apple.com/se/podcast/6.-programming-abstractions/id384232917?i=85092416mt=2

Around 14:50 in the video.

She actually didn't say it was impossible.

--
/Jacob Carlborg

Re: TDD is BS?


On 2013-06-22 17:24, QAston wrote:


I'm not saying that you can't get all of this on your own, yet it's
easier that way. I was a self taught programmer, but I feel that my
knowledge is more complete now (and some of the knowledge is very
important for a systems programmer). It's obviously the same other way
around - you can pass all the exams and get nothing from that. It's up
to you what you're going to do with free time. Important note: public
unis are free in my country, I probably wouldn't study otherwise.


I would say if you want to learn about programming, read these 
newsgroup. I have learned more when reading these newsgroup then I ever 
could at the university. So I just want to say, thank you all.


--
/Jacob Carlborg

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-21 Thread Andrej Mitrovic

On 6/21/13, H. S. Teoh hst...@quickfur.ath.cx wrote:
 In spite of it all, though, we still sometimes end up hiring people who,
 6 months down the road, write code that makes you scratch your head
 going huh?! that genius coder we hired wrote *this* junk?!.

Seems like nowadays it's not too far-fetched to ask for a
github/bitbucket/etc username and see the work they've done, the way
they write code, contribute, etc. It should give a better feel than
any interview.

Re: TDD is BS?


On 2013-06-21 00:18, Nick Sabalausky wrote:


Right. It's like creating a Vacuum Cleaner or a car or a kitchen
appliance by designing the case, housing and controls first, and then
trying to design working internals to fit that mold. Form needs to
follow function.


Ever heard of Apple :)

--
/Jacob Carlborg

Re: TDD is BS?


On 2013-06-21 00:37, Nick Sabalausky wrote:


I'm not saying that it's necessarily bad to write a function's tests
before the function itself, I just don't see what it really matters to
code the tests first. The important thing is that the tests get
written, ideally before you move on to something else. If you have the
discipline to write the tests before the function, then you have the
discipline to write the tests after the function.


I agree. But the point is also, as other has mentioned, that you should 
look from the client's point of view when designing your API. So if you 
write the test firs you're writing the client code first. The you think 
about how the API should look like from the client's point of view. If 
the implementation cannot work or fit in that API you have to change the 
API.


--
/Jacob Carlborg

Re: TDD is BS?


On 2013-06-21 05:32, Nick Sabalausky wrote:


[Snip]

Bottom line is, schools are absolute garbage, and academic
achievement is *at best* completely meaningless.


I couldn't agree more with your post. The problem though is that most 
hiring process uses the HR department, as you mentioned in an other 
post, and they only look at the degree. I only took a degree to have 
something to show for these HR departments, most of what I learned I 
learned on my own time.


--
/Jacob Carlborg

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On 2013-06-21 08:33, Andrej Mitrovic wrote:


Seems like nowadays it's not too far-fetched to ask for a
github/bitbucket/etc username and see the work they've done, the way
they write code, contribute, etc. It should give a better feel than
any interview.


I agree. Most interviews I have been on lately is due to my github project.

--
/Jacob Carlborg

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On 2013-06-21 07:57, H. S. Teoh wrote:


we got to ask HR to first
administer a technical test before any interviews are arranged; test
results are reviewed before deciding to interview the candidate


I done tests like that, they all suck. This is how it usually works:

You get a problem to solve. They say: solve it anyway you want, using 
any language you want. You solve it farily quickly and straight 
forward. Then they say, you are not allowed to use that function. 
Basically they're saying it's cheating. Then you remove that function 
and change the implementation accordingly. Then they say, you are not 
allowed to use that other function. You change the code accordingly and 
this dance continues. Then you're thinking to yourself, Am I supposed 
to reimplement the standard library?.


I would say, most times, it's almost irresponsible to _not_ use the 
standard library. A bunch of people, a lot smarter than I, have had a 
good 20 years or so to perfect and fine tune the standard library. Not a 
chance in hell that I'm going to beat that, on an interview, with code 
written on a whiteboard.


A side note. You're of curse not allowed to look at any documentation at 
all and you're not allowed to use a text editor. You write the code on a 
whiteboard, yes a _whiteboard_.


That's just so stupid. That's not how programming works in the real 
world. Why the hell do they think IDE's have built in, easy to 
read/find, documentation.


--
/Jacob Carlborg

Re: TDD is BS?


On 2013-06-20 22:22, Walter Bright wrote:


Well, it was your example :-)


You got me there :) That's how you're supposed to write TDD according 
most strong believers. But I do some researcher about TDD and similar 
techniques, use my common sense, pick some pieces from here and there 
and use what I think works.


But I also do think that it can be a good idea to at least once or twice 
exactly follow these religious believers and see how it works. Then make 
my own decisions based on that.


--
/Jacob Carlborg

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-21 Thread Andrej Mitrovic

On 6/21/13, Andrej Mitrovic andrej.mitrov...@gmail.com wrote:
 On 6/21/13, Jacob Carlborg d...@me.com wrote:
 I agree. Most interviews I have been on lately is due to my github
 project.

 Oh? That's cool. Which [rpkect?


Looks like I rot13'ed by accident, I meant which project?

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-21 Thread Andrej Mitrovic

On 6/21/13, Jacob Carlborg d...@me.com wrote:
 I agree. Most interviews I have been on lately is due to my github project.

Oh? That's cool. Which [rpkect?

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-21 Thread Paulo Pinto


On Friday, 21 June 2013 at 06:34:09 UTC, Andrej Mitrovic wrote:

On 6/21/13, H. S. Teoh hst...@quickfur.ath.cx wrote:
In spite of it all, though, we still sometimes end up hiring 
people who,
6 months down the road, write code that makes you scratch your 
head

going huh?! that genius coder we hired wrote *this* junk?!.


Seems like nowadays it's not too far-fetched to ask for a
github/bitbucket/etc username and see the work they've done, 
the way
they write code, contribute, etc. It should give a better 
feel than

any interview.


Except not everyone has the authorization to place their work 
code in such public places nor the availability or desire to code 
after work, just to please job interviewers.


--
Paulo

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-21 Thread Wyatt


On Friday, 21 June 2013 at 05:59:00 UTC, H. S. Teoh wrote:
In spite of it all, though, we still sometimes end up hiring 
people who,
6 months down the road, write code that makes you scratch your 
head
going huh?! that genius coder we hired wrote *this* junk?!. 
But maybe

some hiring managers are less discerning than others. *shrug*

In my (admittedly U.S.-centric) experience: if you're getting 
people who know how to use external libraries, what a debugger 
is, more than one programming language (or, indeed, any language 
other than Java), and any form of source control at all, I'm 
afraid you're hitting among the cream of the crop as far as CS 
baccalaureates go.  And if you want them to admin a box at the 
same time, good luck with that.  You're often better off with a 
passionate dropout if you're interested in hiring someone to 
write code.


My hypothesis is this happens because the curricula are heavily 
skewed toward theoretical aspects of computer science. (In my 
view, the exemplar for this was OSU before they axed the 
mandatory RESOLVE/C++ series.)


Cheers,
Wyatt

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On 2013-06-21 12:20, Andrej Mitrovic wrote:


Oh? That's cool. Which [rpkect?


I don't know if it was a particular project but at least one company was 
interested in several projects, DStep (convert C/Objective-C headers to 
D modules), Jazz (D frontend) and Orbit (D package manager).


https://github.com/jacob-carlborg/dstep
https://github.com/jacob-carlborg/jazz
https://github.com/jacob-carlborg/orbit

--
/Jacob Carlborg

Re: TDD is BS?

2013-06-21 Thread deadalnix


On Wednesday, 19 June 2013 at 11:01:05 UTC, Szymon Gatner wrote:
This is not strictly D related but I am very curious about D's 
community opinion on the points made by non other than Jim 
Coplien here:


http://www.tele-task.de/archive/video/flash/16130/

D is the only language (that I am aware of) that has first 
class unit testing support. What do you think? Do we really 
just mentally masturbate?




I finally had time to see the conf. I have to say that I started 
with a bad opinion of it :D But it is simply poorly marketed, the 
content is actually very interesting.


And I'd say it is mostly about OOP rather than TDD. And I agree 
with most of it, while learning some other stuff.

Re: TDD is BS?

On Fri, Jun 21, 2013 at 11:31:22AM +0200, Jacob Carlborg wrote:
 On 2013-06-21 05:32, Nick Sabalausky wrote:
 
 [Snip]
 
 Bottom line is, schools are absolute garbage, and academic
 achievement is *at best* completely meaningless.
 
 I couldn't agree more with your post. The problem though is that
 most hiring process uses the HR department, as you mentioned in an
 other post, and they only look at the degree. I only took a degree
 to have something to show for these HR departments, most of what I
 learned I learned on my own time.
[...]

+1, me too! I can say that 85-90% of what I do at work today, I learned
from my personal coding projects, not from the CS courses I took in
university. (That's why I like to joke about CS grads knowing more about
uncomputable problems than computable ones...)

Having said that, though, I *did* find that going through university
helped train my mind to think logically and rigorously, even if most of
the course content was not actually useful in real-life.


T

-- 
Valentine's Day: an occasion for florists to reach into the wallets of
nominal lovers in dire need of being reminded to profess their
hypothetical love for their long-forgotten.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

On Fri, Jun 21, 2013 at 11:59:12AM +0200, Jacob Carlborg wrote:
 On 2013-06-21 07:57, H. S. Teoh wrote:
 
 we got to ask HR to first administer a technical test before any
 interviews are arranged; test results are reviewed before deciding to
 interview the candidate
 
 I done tests like that, they all suck. This is how it usually works:
 
 You get a problem to solve. They say: solve it anyway you want,
 using any language you want.

Heh, at my job, we're looking for skill in specific languages, so
candidates are explicitly asked to write C code. And this is done not in
an interview setting (which puts too much pressure on the candidate --
can *you* write code in front of interviewers without panicking at least
a bit?), but in a classroom setting. Though, granted, when *I* had to go
through the procedure, it felt like I was taking my CS final exams all
over again. Not exactly a pleasant experience. :-P


 You solve it farily quickly and straight forward. Then they say, you
 are not allowed to use that function. Basically they're saying it's
 cheating. Then you remove that function and change the implementation
 accordingly. Then they say, you are not allowed to use that other
 function. You change the code accordingly and this dance continues.
 Then you're thinking to yourself, Am I supposed to reimplement the
 standard library?.

That's the sign of a poorly-chosen test question. The kind of question I
like to use doesn't focus on nitpicky details like that, but on actual
algorithms or domain-specific knowledge, like showing that the candidate
understands bit operations, pointer arithmetic, and stuff like that. On
that note, it's rather shocking how few candidates know how to use
malloc() and free() correctly...

That's not to say the tests my employer gives have only good
questions, though; there are some that basically do what you describe:
please re-implement strstr(), please concatenate strings without using
strcat(), and the like. When I was involved in hiring, I usually ignore
these questions when evaluating the candidate, or cut them a lot of
slack.

But I do have a slightly evil streak when it comes to technical tests...
once I wrote a Javascript question that requires the candidate to
evaluate what a piece of code does, that involves several nested
closures and variable shadowing. We hired one of the (very) few
candidates who actually got that question right, and she turned out to
be an excellent coder.


 I would say, most times, it's almost irresponsible to _not_ use the
 standard library. A bunch of people, a lot smarter than I, have had
 a good 20 years or so to perfect and fine tune the standard library.
 Not a chance in hell that I'm going to beat that, on an interview,
 with code written on a whiteboard.

Well, I don't think the point of the test is to prove that you can write
code that's *superior* to the standard library, but that you *can* write
non-trivial functionality from ground up.


 A side note. You're of curse not allowed to look at any documentation
 at all and you're not allowed to use a text editor.  You write the
 code on a whiteboard, yes a _whiteboard_.

Well, that's a new one. :-P  Our tests are administered as pen-and-paper
tests. Not unlike CS final exams, unfortunately. :-/


 That's just so stupid. That's not how programming works in the real
 world. Why the hell do they think IDE's have built in, easy to
 read/find, documentation.
[...]

Actually, we instruct HR to provide the standard C library manuals if
candidates ask for it. There *are* some unfair questions that expect you
to know, e.g., the exact order of arguments to select() and stuff like
that, but like I said, it's not HR who evaluates the tests, but the
hiring managers, so it's up to our discretion how much weight we put on
questions like that. We usually disregard minor mistakes like using the
wrong order of arguments to qsort(), if the intent is clear. We don't
(or at least I don't) just blindly look for the highest-scoring test and
hire those candidates; I usually take the time to look at the code and
ask, why did they write it that way?  what does that show about their
coding abilities?.


T

-- 
I see that you JS got Bach.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On 2013-06-21 17:14, H. S. Teoh wrote:


Heh, at my job, we're looking for skill in specific languages, so
candidates are explicitly asked to write C code. And this is done not in
an interview setting (which puts too much pressure on the candidate --
can *you* write code in front of interviewers without panicking at least
a bit?), but in a classroom setting. Though, granted, when *I* had to go
through the procedure, it felt like I was taking my CS final exams all
over again. Not exactly a pleasant experience. :-P


I had four, one hour each, interviews in one afternoon. Afterwards my 
brain was basically fried.



That's the sign of a poorly-chosen test question. The kind of question I
like to use doesn't focus on nitpicky details like that, but on actual
algorithms or domain-specific knowledge, like showing that the candidate
understands bit operations, pointer arithmetic, and stuff like that. On
that note, it's rather shocking how few candidates know how to use
malloc() and free() correctly...


I guess I managed to avoid what they actually wanted to test.


That's not to say the tests my employer gives have only good
questions, though; there are some that basically do what you describe:
please re-implement strstr(), please concatenate strings without using
strcat(), and the like. When I was involved in hiring, I usually ignore
these questions when evaluating the candidate, or cut them a lot of
slack.


I can also understand that it not that easy to create meaningful tests 
like these.



But I do have a slightly evil streak when it comes to technical tests...
once I wrote a Javascript question that requires the candidate to
evaluate what a piece of code does, that involves several nested
closures and variable shadowing. We hired one of the (very) few
candidates who actually got that question right, and she turned out to
be an excellent coder.


Hehe.


Well, I don't think the point of the test is to prove that you can write
code that's *superior* to the standard library, but that you *can* write
non-trivial functionality from ground up.


Yeah, I guess it's hard to find meaningful tests.


Well, that's a new one. :-P  Our tests are administered as pen-and-paper
tests. Not unlike CS final exams, unfortunately. :-/


I hate pen-and-paper tests too. I remember those from the university. I 
understand that they don't want you to have access to a computer with 
access to the internet or a compiler. But come on, can I at least get a 
simple text editor. Half of the time I spend on erasing code because I 
cannot insert new code in the middle of existing code. Then also writing 
those annoying curly braces (the actual symbols) which I never get right.



Actually, we instruct HR to provide the standard C library manuals if
candidates ask for it.


That's generous.


There *are* some unfair questions that expect you
to know, e.g., the exact order of arguments to select() and stuff like
that, but like I said, it's not HR who evaluates the tests, but the
hiring managers, so it's up to our discretion how much weight we put on
questions like that. We usually disregard minor mistakes like using the
wrong order of arguments to qsort(), if the intent is clear. We don't
(or at least I don't) just blindly look for the highest-scoring test and
hire those candidates; I usually take the time to look at the code and
ask, why did they write it that way?  what does that show about their
coding abilities?.


I guess we have different experiences.

--
/Jacob Carlborg

Re: TDD is BS?


On 2013-06-21 16:56, H. S. Teoh wrote:


+1, me too! I can say that 85-90% of what I do at work today, I learned
from my personal coding projects, not from the CS courses I took in
university. (That's why I like to joke about CS grads knowing more about
uncomputable problems than computable ones...)


It feels like there's something wrong with the world here :)

--
/Jacob Carlborg

Re: TDD is BS?

On Fri, Jun 21, 2013 at 05:48:25PM +0200, Jacob Carlborg wrote:
 On 2013-06-21 16:56, H. S. Teoh wrote:
 
 +1, me too! I can say that 85-90% of what I do at work today, I
 learned from my personal coding projects, not from the CS courses I
 took in university. (That's why I like to joke about CS grads knowing
 more about uncomputable problems than computable ones...)
 
 It feels like there's something wrong with the world here :)
[...]

Only something wrong? ;-)

To be fair, though, I can understand why university programs are that
way: their goal is to produce more researchers and professors who may
join the faculty and produce more research. So they focus more on the
theoretical aspects of computer science in order to produce such
candidates, whereas focusing on more practical aspects is something for
technical colleges whose goal is to produce industry workers.

Unfortunately, in North America at least, the technical colleges lean
more toward stuff like how to use MS Word, how to organize your
company data in MS SQL, rather than _real_ programming, and
universities that actually *teach* real programming are more interested
in finding solutions to uncomputable problems than teaching students how
to solve computable ones, so there's a gap in the area of producing
qualified industry coders who can write functional software. There *are*
pockets of competent programming education here and there, of course,
but this is the impression I get from the general situation.


T

-- 
If you think you are too small to make a difference, try sleeping in a closed 
room with a mosquito. -- Jan van Steenbergen

Re: TDD is BS?


On 6/21/2013 3:04 AM, Jacob Carlborg wrote:

But I do some researcher about TDD and similar techniques, use
my common sense, pick some pieces from here and there and use what I think 
works.


I've been around long enough to have seen an endless parade of magic new 
techniques du jour, most of which purport to remove the necessity of thought 
about your programming problem.


In the end they wind up contributing one or two pieces to the collective wisdom, 
and fade away in the rearview mirror.


But there is one technique that stands head and shoulders above the others in 
improving code quality, sometimes dramatically so. That's unit testing coupled 
with a coverage analyzer.


I can't even count the number of times I thought this is so simple, I couldn't 
have gotten it wrong, I doan need no steeenkin unit tests. But I write a couple 
anyway, and you can guess the rest.


Whether you write the unit tests before, during, or after the module is written 
is irrelevant.

Re: TDD is BS?


On 6/20/2013 8:50 PM, H. S. Teoh wrote:

One of my previous supervisors told me that when he gets resumés, as
soon as he sees Ph.D he chucks it straight into the trash.


He'd have missed out on Andrei, then.

Re: TDD is BS?

2013-06-21 Thread John Colvin


On Friday, 21 June 2013 at 19:14:18 UTC, Walter Bright wrote:

On 6/20/2013 8:50 PM, H. S. Teoh wrote:
One of my previous supervisors told me that when he gets 
resumés, as

soon as he sees Ph.D he chucks it straight into the trash.


He'd have missed out on Andrei, then.


And a lot of other people who are driven towards new ideas.

There's a fair amount of inverted snobbery about academia here.

Ultimately, a PhD shows the ability to conduct original research 
and present it. It doesn't make you a great programmer, but then 
again *it never purports to*. Nor does a computer science degree.


If you want a normal programming job, you need to show more real 
world experience than a PhD, but just throwing out people who 
have proved their originality and in depth understanding of a 
topic through a PhD is nothing short of absurd.

Re: TDD is BS?


On 6/21/2013 12:49 PM, John Colvin wrote:

If you want a normal programming job, you need to show more real world
experience than a PhD, but just throwing out people who have proved their
originality and in depth understanding of a topic through a PhD is nothing short
of absurd.


You need a mix of people - young and old, newbies and old hands, academics and 
mechanics, detail guys and big picture guys, to have a healthy dev organization.

Re: TDD is BS?

2013-06-21 Thread Simen Kjaeraas

On Fri, 21 Jun 2013 21:11:51 +0200, Walter Bright  
newshou...@digitalmars.com wrote:


Whether you write the unit tests before, during, or after the module is  
written is irrelevant.


I mostly agree with this, but there is one reason to write tests before
implementing - you don't know the code yet. This way you don't filter out
stuff that you think is unnecessary because you know the code handles it.

Of course, the converse is also true - write tests after writing the code,
because you then know the code and have a better idea of what the corner
cases are.

--
Simen

Re: TDD is BS?

On Fri, Jun 21, 2013 at 09:49:21PM +0200, John Colvin wrote:
 On Friday, 21 June 2013 at 19:14:18 UTC, Walter Bright wrote:
 On 6/20/2013 8:50 PM, H. S. Teoh wrote:
 One of my previous supervisors told me that when he gets resumés, as
 soon as he sees Ph.D he chucks it straight into the trash.
 
 He'd have missed out on Andrei, then.
 
 And a lot of other people who are driven towards new ideas.
 
 There's a fair amount of inverted snobbery about academia here.
 
 Ultimately, a PhD shows the ability to conduct original research and
 present it. It doesn't make you a great programmer, but then again
 *it never purports to*. Nor does a computer science degree.

According to my ex-supervisor (and I'm not saying I agree with him), it
indicates that one is opinionated enough to originate ideas, and
stubborn enough to successfully defend said ideas, which can be
detrimental in a team setting if the idea wasn't a good one.  (And since
a PhD doesn't purport to make you a great programmer, and he was looking
for great programmers rather than researchers, that could be a reason
for his views on the matter.)


 If you want a normal programming job, you need to show more real
 world experience than a PhD, but just throwing out people who have
 proved their originality and in depth understanding of a topic
 through a PhD is nothing short of absurd.

Well, my ex-supervisor *did* have a reputation of having many
interesting (i.e. extreme) ideas about many things. :) I can't say I
subscribe to his views on this matter, but what I was trying to get at
was the prevalent fallacious fixation on academic achievement (i.e.
equating he has good grades / a degree / a PhD with he is a good
programmer).  Too many potential employers can't see beyond that, or
are not willing / don't have the time and energy to do so, thus
resulting in the situation where people are being hired because of their
academic achievement, but are expected to have skills not necessarily
implied by said achievement. Then when such hires consistently produce
sub-par work, some people get provoked to equate PhD with poor
programming skills.

This situation wouldn't have developed if employers evaluated candidates
based on their *skills* rather than by the credentials on paper.  But in
this day and age where time is never enough, it's all too convenient to
dismiss a candidate because he has no academic credentials rather than
to spend the time / energy to review unlikely candidates on the
off-chance that perhaps they might turn out to be hidden programming
prodigies. Or to blindly hire a candidate *with* said credentials
because someone of high academic standing is likely to be skillful
enough to do the job, rather than to spend to time / energy to check if
this is actually the case. (Not to mention that all too often, the ones
with hiring powers may not necessarily have the ability to discern real
skills from a smooth talker.)


T

-- 
You are a very disagreeable person. NO.

Re: TDD is BS?

On Fri, Jun 21, 2013 at 01:11:44PM -0700, Walter Bright wrote:
 On 6/21/2013 12:49 PM, John Colvin wrote:
 If you want a normal programming job, you need to show more real
 world experience than a PhD, but just throwing out people who have
 proved their originality and in depth understanding of a topic
 through a PhD is nothing short of absurd.
 
 You need a mix of people - young and old, newbies and old hands,
 academics and mechanics, detail guys and big picture guys, to have a
 healthy dev organization.

This reminds me of a HR seminar I attended once, where an example was
given of a particular (real) company who only ever hired top-notch
programmers.  They set their standards very high, and have a review
system that would basically fire anyone whose skills are sub-par. The
guys in charge thought this was going to skyrocket the company into
success.

But what actually happened was, nobody wanted to work on mundane
projects -- maintaining existing systems, keeping the servers running,
doing routine chores necessary for everyday operations, etc.. There was
a lot of infighting on who gets to work on the fun stuff, and the people
who didn't get it began to quit one by one. Eventually, none of the
mundane things were adequately taken care of, and most of the employees
left 'cos they didn't get to do what they wanted, and the company
collapsed.


T

-- 
Many open minds should be closed for repairs. -- K5 user

Re: TDD is BS?


On 6/21/2013 1:34 PM, H. S. Teoh wrote:

But what actually happened was, nobody wanted to work on mundane
projects -- maintaining existing systems, keeping the servers running,
doing routine chores necessary for everyday operations, etc.. There was
a lot of infighting on who gets to work on the fun stuff, and the people
who didn't get it began to quit one by one. Eventually, none of the
mundane things were adequately taken care of, and most of the employees
left 'cos they didn't get to do what they wanted, and the company
collapsed.


Yup.

Similar things happen if you only hire people fresh out of college. Things are 
find for a while, and then everyone wants to move up into management at the same 
time.

Re: TDD is BS?

On Fri, Jun 21, 2013 at 12:11:51PM -0700, Walter Bright wrote:
 On 6/21/2013 3:04 AM, Jacob Carlborg wrote:
 But I do some researcher about TDD and similar techniques, use my
 common sense, pick some pieces from here and there and use what I
 think works.
 
 I've been around long enough to have seen an endless parade of magic
 new techniques du jour, most of which purport to remove the
 necessity of thought about your programming problem.
 
 In the end they wind up contributing one or two pieces to the
 collective wisdom, and fade away in the rearview mirror.

+1, words of wisdom.

From high-level language to structured programming to OO to
aspect-oriented programming to X-oriented Y-driven whatever that is
the next bandwagon, it's all the same story repeated over and over.
It's supposed to be the panacea that will make you able to ship a
product just by pressing a single magic button, solve all your
programming problems, and cure world hunger. Then you actually get into
it, and discover that you still have to (gasp!) use your brain to get
your program working. And life goes on as before.


 But there is one technique that stands head and shoulders above the
 others in improving code quality, sometimes dramatically so. That's
 unit testing coupled with a coverage analyzer.
 
 I can't even count the number of times I thought this is so simple,
 I couldn't have gotten it wrong, I doan need no steeenkin unit
 tests. But I write a couple anyway, and you can guess the rest.

Yeah, I used to be firmly in the camp of this code is so trivial, so
*blatantly* correct, that it constitutes its own proof of correctness.
Until D came along and shamed me into writing unittests for said
trivial code, and suddenly I found myself sinking in the flood of
bugs, failing corner cases, and (gasp!) typos, that I hadn't imagined
were there all along.


 Whether you write the unit tests before, during, or after the module
 is written is irrelevant.

Yeah, sometimes I start with one or two tests before, usually a whole
bunch in the middle, and a couple after (followed by a lot more later
when bugs are inevitably found and fixed). The best part about D's
built-in unittests (and I keep harping on about this) is that they're so
dang convenient you'd be foolish for not writing them. They can be
integrated into the very process of coding -- which has singlehandedly
improved the quality of my code by leaps and bounds.


T

-- 
IBM = I'll Buy Microsoft!

Re: TDD is BS?

2013-06-21 Thread Nick Sabalausky

On Fri, 21 Jun 2013 17:48:25 +0200
Jacob Carlborg d...@me.com wrote:

 On 2013-06-21 16:56, H. S. Teoh wrote:
 
  +1, me too! I can say that 85-90% of what I do at work today, I
  learned from my personal coding projects, not from the CS courses I
  took in university. (That's why I like to joke about CS grads
  knowing more about uncomputable problems than computable ones...)
 
 It feels like there's something wrong with the world here :)
 

There definitely is. I spent a total of somewhere around 6 years in
college, but somewhere around the middle of that I made the deliberate
decision to *not* get a degree of any sort. That was because I wanted no
part in helping to perpetuate the incredibly widespread myths/lies about
academic achievement. I've never regretted that decision. (The one
decision I *did* regret was not leaving college entirely after the first
year.)

Re: TDD is BS?

2013-06-21 Thread John Colvin


On Friday, 21 June 2013 at 20:25:28 UTC, H. S. Teoh wrote:

On Fri, Jun 21, 2013 at 09:49:21PM +0200, John Colvin wrote:

On Friday, 21 June 2013 at 19:14:18 UTC, Walter Bright wrote:
On 6/20/2013 8:50 PM, H. S. Teoh wrote:
One of my previous supervisors told me that when he gets 
resumés, as

soon as he sees Ph.D he chucks it straight into the trash.

He'd have missed out on Andrei, then.

And a lot of other people who are driven towards new ideas.

There's a fair amount of inverted snobbery about academia here.

Ultimately, a PhD shows the ability to conduct original 
research and
present it. It doesn't make you a great programmer, but then 
again

*it never purports to*. Nor does a computer science degree.


According to my ex-supervisor (and I'm not saying I agree with 
him), it

indicates that one is opinionated enough to originate ideas, and
stubborn enough to successfully defend said ideas, which can be
detrimental in a team setting if the idea wasn't a good one.  
(And since
a PhD doesn't purport to make you a great programmer, and he 
was looking
for great programmers rather than researchers, that could be a 
reason

for his views on the matter.)


If you want a normal programming job, you need to show more 
real
world experience than a PhD, but just throwing out people who 
have

proved their originality and in depth understanding of a topic
through a PhD is nothing short of absurd.


Well, my ex-supervisor *did* have a reputation of having many
interesting (i.e. extreme) ideas about many things. :) I 
can't say I
subscribe to his views on this matter, but what I was trying to 
get at
was the prevalent fallacious fixation on academic achievement 
(i.e.
equating he has good grades / a degree / a PhD with he is a 
good
programmer).  Too many potential employers can't see beyond 
that, or

are not willing / don't have the time and energy to do so, thus
resulting in the situation where people are being hired because 
of their
academic achievement, but are expected to have skills not 
necessarily
implied by said achievement. Then when such hires consistently 
produce
sub-par work, some people get provoked to equate PhD with 
poor

programming skills.

This situation wouldn't have developed if employers evaluated 
candidates
based on their *skills* rather than by the credentials on 
paper.  But in
this day and age where time is never enough, it's all too 
convenient to
dismiss a candidate because he has no academic credentials 
rather than

to spend the time / energy to review unlikely candidates on the
off-chance that perhaps they might turn out to be hidden 
programming
prodigies. Or to blindly hire a candidate *with* said 
credentials
because someone of high academic standing is likely to be 
skillful
enough to do the job, rather than to spend to time / energy to 
check if
this is actually the case. (Not to mention that all too often, 
the ones
with hiring powers may not necessarily have the ability to 
discern real

skills from a smooth talker.)


T


Agreed on all points.

As an aside: what defines a good programmer  is of course 
dependant on the task. Many academics do write effective code, 
quite quickly, and get a lot of quite convoluted work done by 
coding.


E.g. I would (entirely hypothetically) happily hire a physics PhD 
to write high-level data-analysis routines in python, but i'd be 
wary of getting them to work on a high security web-app. On the 
flip side, I would be wary of hiring an enthusiastic college 
dropout to write an accurate fluid simulation, but they might 
easily fit the definition of good programmer for extending a 
web framework.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-21 Thread Andrei Alexandrescu


On 6/21/13 5:59 AM, Jacob Carlborg wrote:

On 2013-06-21 07:57, H. S. Teoh wrote:


we got to ask HR to first
administer a technical test before any interviews are arranged; test
results are reviewed before deciding to interview the candidate


I done tests like that, they all suck. This is how it usually works:

You get a problem to solve. They say: solve it anyway you want, using
any language you want. You solve it farily quickly and straight
forward. Then they say, you are not allowed to use that function.
Basically they're saying it's cheating. Then you remove that function
and change the implementation accordingly. Then they say, you are not
allowed to use that other function. You change the code accordingly and
this dance continues. Then you're thinking to yourself, Am I supposed
to reimplement the standard library?.

I would say, most times, it's almost irresponsible to _not_ use the
standard library. A bunch of people, a lot smarter than I, have had a
good 20 years or so to perfect and fine tune the standard library. Not a
chance in hell that I'm going to beat that, on an interview, with code
written on a whiteboard.

A side note. You're of curse not allowed to look at any documentation at
all and you're not allowed to use a text editor. You write the code on a
whiteboard, yes a _whiteboard_.

That's just so stupid. That's not how programming works in the real
world. Why the hell do they think IDE's have built in, easy to
read/find, documentation.


If there's any need to reach for documentation, the interviewer has 
failed. When interviewing we (at Facebook) ask problems that are likely 
to appear in a normal day's work, but for which the typical libraries 
don't help. (E.g. many libraries don't can't help with implementing 
unstable remove (see std.algorithm).)


Also it's fair to ask about implementing a stdlib function itself if the 
interview concerns some systems-level work; e.g. brute-force strstr() is 
fair game and I think any engineer should be able to lift it off the 
ground quickly (to my dismay, only a fraction can). Paradoxically use of 
stdlib functions may actually hurt; I've seen people who e.g. call 
strlen() in a loop in order to implement strstr()!



Andrei

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

On Friday, 21 June 2013 at 21:33:43 UTC, Andrei Alexandrescu 
wrote:
brute-force strstr() is fair game and I think any engineer 
should be able to lift it off the ground quickly (to my dismay, 
only a fraction can).


But, should the return value be const or not? :P


I think I'd write in D just cuz of inout().

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

On Fri, Jun 21, 2013 at 05:33:45PM -0400, Andrei Alexandrescu wrote:
[...]
 Also it's fair to ask about implementing a stdlib function itself if
 the interview concerns some systems-level work; e.g. brute-force
 strstr() is fair game and I think any engineer should be able to
 lift it off the ground quickly (to my dismay, only a fraction can).

Yeah, I was rather dismayed at how many people lacked basic
understanding of the programming language they purport to be skilled in.
Like not understanding variable shadowing in C, or simple closures in
Javascript (not the evilly-nested convolution I tested for in a
different test question :-P).


 Paradoxically use of stdlib functions may actually hurt; I've seen
 people who e.g. call strlen() in a loop in order to implement
 strstr()!
[...]

My favorite example of poor strlen() usage is writing strlen()==0 in a
loop condition.

More typical causes of disqualification, though, are what one of my
university professors affectionately called squirrelly code: code that
*probably* does what it's supposed to, but does so by roundabout,
non-obvious ways, running around here and there doing little things that
don't really relate directly to the problem at hand (like squirrels
running around hunting for their forgotten stash of nuts). Code like
this typically demonstrate a lack of understanding of programming in
general, or lack of understanding of the problem at hand, or inability
to identify and address the salient points of said problem. Typical
symptoms include declaring and using useless variables, calling printf
inside a function that shouldn't be doing I/O, doing unnecessary type
conversions to perform trivial computations (converting int to string
and attempting to do arithmetic on the digits in the string), odd usage
of loops and conditionals in unexpected places, using comments to urge
the computer to do what one wishes, etc..

The software analogue of Rube Goldberg machines, if you will. :-P


T

-- 
Век живи - век учись. А дураком помрёшь.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

Just for laughs I just slapped together a strstr and it made me 
realize a little thing I do in D that I never did in C:


assert()

I use it all over the place in D, pretty much any time I make an 
assumption, I slap it down in an assert.


But I don't I ever, not once, used any kind of assertion in C or 
C++. I think this is a fairly significant gain that can be 
attributed to it being built in to D. It is just silly not to do 
it when it is there.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On Friday, 21 June 2013 at 22:23:01 UTC, Adam D. Ruppe wrote:

being built in to D


Or maybe it is because everybody else does it in the 
documentation and such, since #include assert.h in C isn't 
*that* big of a deal. idk, all I do know for sure is that I do it 
now and didn't before.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-21 Thread Andrei Alexandrescu


On 6/21/13 2:50 PM, Adam D. Ruppe wrote:

On Friday, 21 June 2013 at 21:33:43 UTC, Andrei Alexandrescu wrote:

brute-force strstr() is fair game and I think any engineer should be
able to lift it off the ground quickly (to my dismay, only a fraction
can).


But, should the return value be const or not? :P


I think I'd write in D just cuz of inout().


That would be a nice touch and bring bonus points, but in most of the 
cases I tell the candidate to gloss over that detail.


Andrei

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

2013-06-21 Thread Andrei Alexandrescu


On 6/21/13 3:22 PM, Adam D. Ruppe wrote:

Just for laughs I just slapped together a strstr


Post it and I'll destroy it.

Andrei

Re: TDD is BS?

2013-06-21 Thread Nick Sabalausky

On Fri, 21 Jun 2013 09:47:46 -0700
H. S. Teoh hst...@quickfur.ath.cx wrote:
 
 universities that actually *teach* real programming are more
 interested in finding solutions to uncomputable problems than
 teaching students how to solve computable ones
 

That doesn't match my experience (also in the US here). Granted, all my
info is from ten years ago, but what I saw was mainly a bunch of what
The Joel on Software guy called Java Schools
http://www.joelonsoftware.com/articles/ThePerilsofJavaSchools.html.

The following includes what I've seen at BGSU and OSU (party schools,
not that I personally attended OSU, but I did have a friend that went
through OSU's RESOLVE/C++ stuff) and also JCU (a private univ that,
at least around Cleveland, is highly-regarded by everyone except me).

What I've seen at these places, and apparently many others from what I
understand, is that while they *do* recognize the importance of creating
programmers, the problems are:

- The theory is minimal to make sure they get all those high-paying
  students through the revolving door.

- Tests and exams do *not* teach people. An yet, that's where the
  emphasis is, instead of on instruction.

- The really *big* issue: You just simply CANNOT expect people to go
  from beginner to competent programmer when they spend *at most*
  one-third of their credits, and about 3 hours a week, over a mere 4
  years on actual programming material instead of irrelevant liberal
  arts garbage that *belongs* in high school, not a college so-called
  major.

- The nasty little details like pointer/memory problems, linker errors,
  etc that real people have to deal with are neatly glossed over and
  sidestepped.

- There was one CS101 teacher (I had to tutor her unfortunate students)
  who constantly bragged about being from a real-world software
  company...but she was a Java-addict (circa v1.2-v1.4) who kept trying
  to teach OO *before* basic flow-of-execution. Consequently, none of
  her unfortunate students had the slightest clue what was going on.

- Many of the professors are terrible programmers themselves. For
  example, I had one who openly admitted the only language he knew was
  C, and yet at one point it became painfully obvious that he had
  almost no comprehension of null-terminated strings.

- Many of the teachers don't even teach, they just collect the
  thousands of dollars in tuition and give you a book recommendation
  (really more of a demand than a recommendation). Now, I'm a strong
  believer in being self-taught and learning from books, but all I need
  for that is a library card, not a $100k debt and four years of elitist
  attitudes from people who clearly don't know what they're doing
  anyway.

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)


On 6/21/2013 3:35 PM, Andrei Alexandrescu wrote:

On 6/21/13 3:22 PM, Adam D. Ruppe wrote:

Just for laughs I just slapped together a strstr


Post it and I'll destroy it.


Can I play, too? Mine from the Digital Mars C library. Haven't looked at it 
since 2001.

==

/*_ strstr.c */
/* Copyright (C) 1985-2001 by Digital Mars  */
/* All Rights Reserved  */
/* www.digitalmars.com  */
/* Written by Walter Bright */

#includestdio.h
#includectype.h
#includestddef.h
#includestring.h
#includestdlib.h

#if 0 /* Smaller but slower under many circumstances. */
char *strstr(const char *s1,const char *s2)
{   size_t len2;
size_t len1;
char c2 = *s2;

len1 = strlen(s1);
len2 = strlen(s2);
if (!len2)
return (char *) s1;
while (len2 = len1)
{
if (c2 == *s1)
if (memcmp(s2,s1,len2) == 0)
return (char *) s1;
s1++;
len1--;
}
return NULL;
}
#else
#include limits.h/* defines UCHAR_MAX */
/
See Algorithms Second Edition by Robert Sedgewick.  Boyer-Moore string
search routine.
/
char *strstr(const char *text, const char * pattern)
{
  const size_t M = strlen(pattern);
  const unsigned long N = strlen(text);
  const char *p_p = pattern;
  const char *t_p;
  size_t skip[UCHAR_MAX + 1];
  size_t i, j;

  if(M == 0)
return (char *)text;

  if(M  N)   /* If pattern is longer than the text string. */
return 0;

#if __INTSIZE == 4
  _memintset((int *)skip, M, UCHAR_MAX + 1);
#else
  { size_t *s_p = skip + UCHAR_MAX;
do
{
  *s_p = M;
}while(s_p--  skip);
  }
#endif

  p_p = pattern;
  do
  {
skip[*(const unsigned char *)p_p] = M - 1 - (p_p - pattern);
  } while(*++p_p);

  p_p = pattern + M - 1;
  t_p = text + M - 1;

  while(1)
  {
char c;

c = *t_p;
if(c == *p_p)
{
  if(p_p - pattern == 0)
return (char *)t_p;

  t_p--; p_p--;
}
else
{
  size_t step = M - (p_p - pattern);

  if (step  skip[(unsigned char)c])
step = skip[(unsigned char)c];

  /* If we have run out of text to search in. */
  /* Need cast for case of large strings with 16 bit size_t... */
  if((unsigned long)(t_p - text) + step = N)
return 0;

  t_p += step;

  p_p = pattern + M - 1;
}
  }
}
#endif  /* #if 0 */

Re: TDD is BS?

On Fri, Jun 21, 2013 at 06:12:57PM -0400, Nick Sabalausky wrote:
 On Fri, 21 Jun 2013 09:47:46 -0700
 H. S. Teoh hst...@quickfur.ath.cx wrote:
  
  universities that actually *teach* real programming are more
  interested in finding solutions to uncomputable problems than
  teaching students how to solve computable ones
  
 
 That doesn't match my experience (also in the US here).

Actually, I'm up in the Great White North, so my perception of North
America may be a bit biased on the first word. :-P


 Granted, all my info is from ten years ago, but what I saw was mainly
 a bunch of what The Joel on Software guy called Java Schools
 http://www.joelonsoftware.com/articles/ThePerilsofJavaSchools.html.

LOL... that article made me laugh. Thanks for the great read!


 The following includes what I've seen at BGSU and OSU (party schools,
 not that I personally attended OSU, but I did have a friend that went
 through OSU's RESOLVE/C++ stuff) and also JCU (a private univ that,
 at least around Cleveland, is highly-regarded by everyone except me).
 
 What I've seen at these places, and apparently many others from what I
 understand, is that while they *do* recognize the importance of
 creating programmers, the problems are:
 
 - The theory is minimal to make sure they get all those high-paying
   students through the revolving door.

Huh. I had the opposite experience. We were pounded with so much theory
from day one, and then summarily executed on our Computability Theory
finals (the infamous exam that was so hard, you were allowed to bring
*anything* -- any textbook, reference book, your desktop PC if you were
so inclined -- and none of it would help), that I came out with a rather
strong distaste for anything that mentions the word computability,
lasting for quite a while before it wore off.


 - Tests and exams do *not* teach people. An yet, that's where the
   emphasis is, instead of on instruction.
 
 - The really *big* issue: You just simply CANNOT expect people to go
   from beginner to competent programmer when they spend *at most*
   one-third of their credits, and about 3 hours a week, over a mere 4
   years on actual programming material instead of irrelevant liberal
   arts garbage that *belongs* in high school, not a college so-called
   major.

That, I have to agree. I wanted to double-major in CS and Chemistry, but
gave up on the first day in 2nd year when I looked at my course / lab /
programming project schedule, and said, that's not gonna work. Without
adequate time actually spent programming, it's impossible to get good at
it.


 - The nasty little details like pointer/memory problems, linker errors,
   etc that real people have to deal with are neatly glossed over and
   sidestepped.

OK, that's one of my pet peeves. Back in the day, I was taught pointers
(though not linker errors -- I learnt that on my own) and recursion.
Nowadays, people hear the word pointer and go e, and when you
say recursion their eyes glaze over. What on earth did they do to the
CS programs?!


 - There was one CS101 teacher (I had to tutor her unfortunate students)
   who constantly bragged about being from a real-world software
   company...but she was a Java-addict (circa v1.2-v1.4) who kept trying
   to teach OO *before* basic flow-of-execution. Consequently, none of
   her unfortunate students had the slightest clue what was going on.

Ugh. Talk about putting the cart before the horse...


 - Many of the professors are terrible programmers themselves. For
   example, I had one who openly admitted the only language he knew was
   C, and yet at one point it became painfully obvious that he had
   almost no comprehension of null-terminated strings.

That's the beef I have with over-emphasis on CS theory. There's nothing
wrong with theory in and of itself -- in fact it's foundational and very
much indispensible -- but when you become so detached from reality that
you think in terms of pure idealizations -- when you can *only* think in
terms of pure idealizations -- that you can't even write a single line
of real code without some external help, then something has clearly gone
very, very wrong.


 - Many of the teachers don't even teach, they just collect the
   thousands of dollars in tuition and give you a book recommendation
   (really more of a demand than a recommendation).

That's because the incentives are all wrong. Professors aren't paid to
teach; they're paid to produce research. Publish or perish, so goes the
saying in those circles. To them, teaching is an additional burden
imposed upon them that they'd rather get over with ASAP and get back to
their research, whatever it takes. Turn away the students showing up at
your office hours. Bore them to death in class so they wouldn't know
*what* to ask even if they wanted to. Read from a photocopy of the
textbook word-for-word to pass lecture time with zero effort (I've
actually been in a class where this was done). Anything, to get it over
with and get back

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)

On Friday, 21 June 2013 at 22:35:55 UTC, Andrei Alexandrescu 
wrote:

Post it and I'll destroy it.



inout(char)* mystrstr(inout(char)* haystack, const(char*) needle) 
{

assert(haystack !is null);

if(needle is null)
return haystack;

const(char)* where = needle;
inout(char)* gotit;

while(*haystack) {
if(*haystack == *where) {
if(gotit is null)
gotit = haystack; // store where the match started
where++;
haystack++;
if(*where == 0)
return gotit;
} else {
// if we were in the middle of a match, we'll want to
// check the current character again so only advance 
if

// we're at the beginning
if(gotit is null)
haystack++;
else {
// partial match, but not complete so no good
// start over, including the current *haystack
where = needle;
gotit = null;
}
}
}

return null;
}


unittest {
void test(string haystack, string needle, size_t line = 
__LINE__) {

import core.stdc.string;
import std.conv;

// .ptr is fine because the test uses all string 
literals, which are 0 terminated automatically
assert(strstr(haystack.ptr, needle.ptr) is 
mystrstr(haystack.ptr, needle.ptr), to!string(line));

}

test(foobar, f);
test(foobar, ob);
test(foobar, o);
test(foobar, a);
test(foobar, ar);
test(foobar, ea);

test(bedtime bedazzled!, beda);
}




I've heard of Boyer-Moore but don't actually know it, so I'd have 
to look it up! The brute force loop is simple enough though 
without needing a great deal of thought, though my first run 
through did actually fail the unittest, since I neglected the 
commented section in the else{} part. So if I was doing it on a 
whiteboard, (or didn't immediately use foo as a test variable, 
with the repeated o) I might not have actually caught that!

Re: OT: CS education gone wrong (Was: Re: TDD is BS?)