Re: Why is the constructor of B called?
On Thursday, 24 September 2015 at 01:01:09 UTC, Nicholas Wilson
wrote:
On Wednesday, 23 September 2015 at 21:25:15 UTC, tcak wrote:
On Wednesday, 23 September 2015 at 21:14:17 UTC, Adam D. Ruppe
wrote:
On Wednesday, 23 September 2015 at 21:08:37 UTC, tcak wrote:
I wouldn't expect B's constructor to be called at all unless
"super" is used there.
"If no call to constructors via this or super appear in a
constructor, and the base class has a constructor, a call to
super() is inserted at the beginning of the constructor. "
from http://dlang.org/class.html#constructors
the idea is to make sure the base class construction work is
done too.
Is there any way to prevent this behaviour?
Quickly checked whether Java acts in the same way. Answer is
yes.
You might be able to swap out the vtbl entry for a stub call
it and trick the compiler and swap it back, but...
Urgh...
If you can modify the base class, and you really need it, you can
check the dynamic type:
class Base {
this() {
if(!cast(Base) this) return;
// do the initialization
}
}
Re: Maximum number of threads
On Thursday, September 24, 2015 08:55:22 Alex via Digitalmars-d-learn wrote: > This should be a not so long question to answer, I hope. > > I took an example from the "Programming in D" book, chapter > "Message Passing Concurrency", around page 550. The question of > interest was, how many threads I can have spawned at the same > time. > So I made an array of robot objects from the example and found > out: the maximum number is different on different PCs I have. > For example: > - on my mac I can have 2048 threads spawned at the same time > - on my linux machine the maximum number is 32192. > The numbers are quite fixed, however there were some small > fluctuations on the linux machine. > > The questions still remains: how do I know, what maximum number > of threads I can have? Is it possible to calculate this value > during runtime of my program? The two machines I have available > for testing are very different, what is the main parameter which > controls the number of possible threads? (CPU maybe? Number of > cores? RAM is not I think at the moment...) It's entirely system specific. Not only does every OS handle it differently, but it con depend on how your machine is configured. In general though, I believe that it's a hard limit in the OS and has nothing to do with the number of cores or amount of RAM in your machine (though even if you haven't hit the limit, if the OS doesn't have enough resources to create another thread, then it will fail). So, if you want to know for a particular OS, you're probably going to have to google for it. In the case of linux, a quick search seems to indicate that getrlimit will do the trick: http://linux.die.net/man/2/getrlimit But you can find as much pretty quickly googling yourself. Maybe someone else can tell you what to use on other OSes off the top of their head though. Regardless, D doesn't provid any special way to do this, so to figure it out, you'd be calling whatever the C functions are that will tell you. - Jonathan M Davis
Re: Dub package with C code
On Thursday, 24 September 2015 at 08:35:40 UTC, Edwin van Leeuwen wrote: Alternatively you could use reggea to build both. I want to use dub. Simply because of code.dlang.org. Or can reggae also pull packages from there? You could try including the c source in your repo and add preBuildCommands to the dub config which builds the static library. preBuildCommands seems to be the way to go. Thank you all.
Re: Maximum number of threads
On Thursday, 24 September 2015 at 08:55:25 UTC, Alex wrote: This should be a not so long question to answer, I hope. I took an example from the "Programming in D" book, chapter "Message Passing Concurrency", around page 550. The question of interest was, how many threads I can have spawned at the same time. So I made an array of robot objects from the example and found out: the maximum number is different on different PCs I have. For example: - on my mac I can have 2048 threads spawned at the same time - on my linux machine the maximum number is 32192. The numbers are quite fixed, however there were some small fluctuations on the linux machine. The questions still remains: how do I know, what maximum number of threads I can have? Is it possible to calculate this value during runtime of my program? The two machines I have available for testing are very different, what is the main parameter which controls the number of possible threads? (CPU maybe? Number of cores? RAM is not I think at the moment...) Thanks in advance Alex From the numbers (2048 = 2^11, 32192 = ca 2^15), it's clear that you're not running out of memory, but that these are artificial limits imposed by the OS. This stackoverflow answer describes the situation on Linux: http://unix.stackexchange.com/a/47600/34768
Re: Maximum number of threads
On Thursday, 24 September 2015 at 08:55:25 UTC, Alex wrote: - on my mac I can have 2048 threads spawned at the same time - on my linux machine the maximum number is 32192. The numbers are quite fixed, however there were some small fluctuations on the linux machine. I only know of `cat /proc/sys/kernel/threads-max` on linux, which will give you the max number of threads system-wide.
Re: Dub package with C code
On 24/09/15 5:51 PM, Sebastiaan Koppe wrote: On Thursday, 24 September 2015 at 04:17:14 UTC, Rikki Cattermole wrote: Is libxlsxwriter available in the systems package manager? Pacman says no. Let e.g. Windows users figure theirs out. libxlsxwriter is not supported on windows. Which is kind-of funny. I've taken a look at it. Why not just port it?
Re: Dub package with C code
On Thursday, 24 September 2015 at 06:00:50 UTC, Rikki Cattermole wrote: On 24/09/15 5:51 PM, Sebastiaan Koppe wrote: On Thursday, 24 September 2015 at 04:17:14 UTC, Rikki Cattermole wrote: Is libxlsxwriter available in the systems package manager? Pacman says no. Let e.g. Windows users figure theirs out. libxlsxwriter is not supported on windows. Which is kind-of funny. I've taken a look at it. Why not just port it? Because I want to focus on the product I am building right now, not on side-projects.
Maximum number of threads
This should be a not so long question to answer, I hope. I took an example from the "Programming in D" book, chapter "Message Passing Concurrency", around page 550. The question of interest was, how many threads I can have spawned at the same time. So I made an array of robot objects from the example and found out: the maximum number is different on different PCs I have. For example: - on my mac I can have 2048 threads spawned at the same time - on my linux machine the maximum number is 32192. The numbers are quite fixed, however there were some small fluctuations on the linux machine. The questions still remains: how do I know, what maximum number of threads I can have? Is it possible to calculate this value during runtime of my program? The two machines I have available for testing are very different, what is the main parameter which controls the number of possible threads? (CPU maybe? Number of cores? RAM is not I think at the moment...) Thanks in advance Alex
Re: Dub package with C code
On Thursday, 24 September 2015 at 06:21:02 UTC, Sebastiaan Koppe wrote: Because I want to focus on the product I am building right now, not on side-projects. You could try including the c source in your repo and add preBuildCommands to the dub config which builds the static library. Alternatively you could use reggea to build both.
Re: Maximum number of threads
Offtop: i think if number of threads > number of real cores, than there's something wrong with your design. Maybe fibers suit better ?
question about multiple alias this
class A{
int i;
bool b;
alias i this;
alias b this;
}
void main()
{
auto a = new A;
int i = a;
bool b = a;
}
--- this will not compile in dmd 2068.1.
--- ok, but what technique do you use to emulate this type of
behavior??
--- would interfaces be the answer, if so could I see an example.
and would you use the
--- same for structs ??
--- thanks, Steven
Re: Why is the constructor of B called?
On Thursday, 24 September 2015 at 11:26:12 UTC, Marc Schütz wrote:
On Thursday, 24 September 2015 at 01:01:09 UTC, Nicholas Wilson
wrote:
On Wednesday, 23 September 2015 at 21:25:15 UTC, tcak wrote:
On Wednesday, 23 September 2015 at 21:14:17 UTC, Adam D.
Ruppe wrote:
[...]
Is there any way to prevent this behaviour?
Quickly checked whether Java acts in the same way. Answer is
yes.
You might be able to swap out the vtbl entry for a stub call
it and trick the compiler and swap it back, but...
Urgh...
If you can modify the base class, and you really need it, you
can check the dynamic type:
class Base {
this() {
if(!cast(Base) this) return;
// do the initialization
}
}
doesn't upcasting always work? iirc only down casting can return
null.
Re: Why is the constructor of B called?
On 09/24/15 13:26, Marc Schütz via Digitalmars-d-learn wrote:
> On Thursday, 24 September 2015 at 01:01:09 UTC, Nicholas Wilson wrote:
>> On Wednesday, 23 September 2015 at 21:25:15 UTC, tcak wrote:
>>> On Wednesday, 23 September 2015 at 21:14:17 UTC, Adam D. Ruppe wrote:
On Wednesday, 23 September 2015 at 21:08:37 UTC, tcak wrote:
> I wouldn't expect B's constructor to be called at all unless "super" is
> used there.
"If no call to constructors via this or super appear in a constructor, and
the base class has a constructor, a call to super() is inserted at the
beginning of the constructor. "
from http://dlang.org/class.html#constructors
the idea is to make sure the base class construction work is done too.
>>>
>>> Is there any way to prevent this behaviour?
>>>
>>> Quickly checked whether Java acts in the same way. Answer is yes.
>>
>> You might be able to swap out the vtbl entry for a stub call it and trick
>> the compiler and swap it back, but...
>
> Urgh...
>
> If you can modify the base class, and you really need it, you can check the
> dynamic type:
>
> class Base {
> this() {
> if(!cast(Base) this) return;
> // do the initialization
> }
> }
If you're going to do this then you can just use overloading.
That will both avoid the runtime check and require the hack
to be explicitly enabled in the derived class. IOW:
class B {
this() {
writeln("B.constructor");
foo();
}
struct SkipBCtor {}
this(SkipBCtor) {}
void foo() {
writeln("B.foo");
}
}
class D : B {
this() {
super(SkipBCtor());
writeln("D.constructor");
}
override void foo() {
writeln("D.foo overrides B.foo");
}
}
artur
Re: ORM libraries for D
On 25/09/15 1:18 AM, David Nadlinger wrote: Hi all, I'm having a look at ORM libraries in D right now. So far, I've come across hibernated and dvorm. Are there any other libraries that I should have a look at, particularly actively maintained ones? dvorm and hibernated seem to have received no work during the last couple of months. — David Dvorm is more or less feature complete :) I am the author of it, but unless issues come up I do not intend to continue working upon it. I have another one being worked upon but think 2 year plan. There are many more important libraries to fill my time with, unfortunately.
Re: ORM libraries for D
On 25/09/15 1:30 AM, Edwin van Leeuwen wrote: On Thursday, 24 September 2015 at 13:24:14 UTC, Rikki Cattermole wrote: Dvorm is more or less feature complete :) I am the author of it, but unless issues come up I do not intend to continue working upon it. You could consider bumping it up to version 1.0.0 to highlight this. Put it this way, doing so would also bump it up on code.dlang.org. I have not even ran the unittests in like a year. So who knows if it compiles with 2.068. But nobody has complained so lets assume yes.
Re: ORM libraries for D
On Thursday, 24 September 2015 at 13:24:14 UTC, Rikki Cattermole wrote: Dvorm is more or less feature complete :) I am the author of it, but unless issues come up I do not intend to continue working upon it. You could consider bumping it up to version 1.0.0 to highlight this.
Re: Dub package with C code
On Thursday, 24 September 2015 at 06:21:02 UTC, Sebastiaan Koppe wrote: Because I want to focus on the product I am building right now, not on side-projects. We should write a C to D converter. We have htod but I'm talking the whole source of it. That might be useful for times like this. But I have other things to do too...
Re: ORM libraries for D
On 25/09/15 1:43 AM, David Nadlinger wrote: On Thursday, 24 September 2015 at 13:24:14 UTC, Rikki Cattermole wrote: Dvorm is more or less feature complete :) I am the author of it, but unless issues come up I do not intend to continue working upon it. Do you know whether somebody has written an SQLite provide for it? I was going to use SQLite initially, hoping to just switch to MySQL/PostgreSQL later in case I unexpectedly need more than that later. — David As far as I am aware no. Although I would recommend against taking it up unless you feel like taking ownership of it(Dvorm).
ORM libraries for D
Hi all, I'm having a look at ORM libraries in D right now. So far, I've come across hibernated and dvorm. Are there any other libraries that I should have a look at, particularly actively maintained ones? dvorm and hibernated seem to have received no work during the last couple of months. — David
Re: ORM libraries for D
On Thursday, 24 September 2015 at 13:24:14 UTC, Rikki Cattermole wrote: Dvorm is more or less feature complete :) I am the author of it, but unless issues come up I do not intend to continue working upon it. Do you know whether somebody has written an SQLite provide for it? I was going to use SQLite initially, hoping to just switch to MySQL/PostgreSQL later in case I unexpectedly need more than that later. — David
Client socket sending data only one time.
Hello
I'm trying to connect to server and send data, with such simple
client:
#!/usr/bin/rdmd
import std.stdio;
import std.socket;
import std.socketstream;
import std.process;
import std.conv;
import core.time;
void main()
{
char[1024] buffer = 0;
Socket client = new TcpSocket();
auto addrServer = new InternetAddress("localhost", 8080);
client.connect(addrServer);
while(1)
{
client.send(readln());
client.receive(buffer);
writeln(buffer);
buffer = 0;
}
}
It is working but only one time, when I'm trying to send again
(second loop of while) it's stooping on readln() but not sending
input data.
What am i missing here?
Thanks in advance for any help.
Re: dis...@dlang.org
On Wednesday, 23 September 2015 at 17:43:43 UTC, Ali Çehreli wrote: On 09/23/2015 06:01 AM, Aidan wrote: I am just starting to look into D and i have to say I am loving it at the moment. But I have ran into an issue that i can't seem to find any libraries for Api hooking. If anyone knows of a well documented source for this it would be much appreciated. I don't understand the question but it may be related to lack of fiber in one's diet: :) http://vibed.org/features#fibers http://ddili.org/ders/d.en/fibers.html Ali I am reading your book On D at the moment! finding it very useful.
Re: dis...@dlang.org
On Wednesday, 23 September 2015 at 18:09:22 UTC, novice2 wrote: http://forum.dlang.org/thread/hrzfcjrltftgzansd...@forum.dlang.org https://github.com/Trass3r/hooksample Yes this is what I was looking for. thank you.
Re: question about multiple alias this
On Thursday, September 24, 2015 13:04:20 steven kladitis via
Digitalmars-d-learn wrote:
> class A{
>int i;
>bool b;
>alias i this;
>alias b this;
> }
>
> void main()
> {
>auto a = new A;
>int i = a;
>bool b = a;
> }
>
> --- this will not compile in dmd 2068.1.
> --- ok, but what technique do you use to emulate this type of
> behavior??
> --- would interfaces be the answer, if so could I see an example.
> and would you use the
> --- same for structs ??
> --- thanks, Steven
The only implicit conversion that's built into user-defined types is casting
from a derived class to a base class or interface that it implements. All
other implicit conversions have to be implemented via alias this, and
currently, you can only have one alias this. So, what you're trying to do
really doesn't work right now. You could declare an opCast for each type you
want to be able to convert to and do explicit casts, but alias this is the
only way to add implicit conversions.
We'll probably have support for multiple alias thises at some point, but I
don't know when.
- Jonathan M Davis
Re: Dub package with C code
On Thursday, 24 September 2015 at 02:43:20 UTC, Sebastiaan Koppe wrote: I have just created bindings for libxlsxwriter, an c library for creating excel files. Used the htod tool to do most of the work, and only had to adjust some things - mainly because libxlsxwriter uses data structures written in macro's. Right now I am making a dub package and I would like to aim for convenience for end-users (read: me). Therefor I decided to include the compiled static library inside the package. I only use Linux 64-bit myself, but this is obviously limiting for other people. The other option I had was to include the whole c code, depend on gcc or clang, and have dub (somehow) first build libxlsxwriter. But that seemed a bit too much... Another option would be to require end-users to build libxlsxwriter themselves. What do you guys recommend? nice work! worth a little blog post on the experience so others can be inspired by and benefit from yours?
Re: Maximum number of threads
On Thursday, 24 September 2015 at 12:38:41 UTC, Temtaime wrote: Offtop: i think if number of threads > number of real cores, than there's something wrong with your design. Maybe fibers suit better ? Well... you got my idea :) So it is not so far offtop, as you think ))) Fibers DO suit better as an idea of light workers. But the problem I have to manage is, that my program has to incorporate unpredictability in the work cycle of my workers. It is one of the main idea of the process itself. So the fact that a fiber yields at fixed points of his work is just the opposite from what I want. But the portability of code is an issue too... and my tries show, that I can't rely on this with threads... Having said that, I got an idea today, how I could try to incorporate fibers for my needs. If I manage to hide the yields calls of my workers in some random environment, I could express, that a worker can but must not give up his control at a specific point of his work. I have to try this idea next days. Using fibers instead of threads would save me from a lot of troubles anyway... ;) Thanks to everybody for hints about my question!
Re: How to setup mono-D for shared libraries?
On Wednesday, 23 September 2015 at 04:34:45 UTC, Rikki Cattermole wrote: On 23/09/15 8:20 AM, Jacob wrote: How do I setup mono-D for creating shared libraries and including them into other projects? When I drag the .d files to create the library from, which is not my own, I get undefined references. I have the lib files, which are a bunch of separate libs, that I want to include into one big lib. Once that's done I want to include that lib into another project. I'd rather not modify si.ini. Are there any tutorials for getting started with Mono-D? (setup, not coding) Well you could go the route of dub, which configuration files can be loaded directly into it as a project. To create the library, what do I do? 'dub init myLib' then delete app.d, and then add all the library.d files? Then what? Where do I tell it to find the .lib files without adding them to sc.ini? Do I just mess with dub.json to and add all the proper build options to get both the lib and the dependent apps working or are there other steps I'm missing?
Re: Dub package with C code
On Thursday, 24 September 2015 at 18:19:49 UTC, Laeeth Isharc wrote: nice work! To be honest it took me 2 hours, starting from git clone worth a little blog post on the experience so others can be inspired by and benefit from yours? I would be happy to write something. Any particular blog platform? Or do I first have to roll out my own?
Re: Dub package with C code
On Thursday, 24 September 2015 at 12:55:12 UTC, Adam D. Ruppe wrote: On Thursday, 24 September 2015 at 06:21:02 UTC, Sebastiaan Koppe wrote: Because I want to focus on the product I am building right now, not on side-projects. We should write a C to D converter. We have htod but I'm talking the whole source of it. That might be useful for times like this. But I have other things to do too... It would be really cool to have that. But aren't there a lot of corner cases that require manual intervention? Having said that, htod has been invaluable. And if I decide to port it, ctod will be invaluable as well, even though it won't get it 100% right.
Re: Dub package with C code
On Thursday, 24 September 2015 at 11:38:08 UTC, Sebastiaan Koppe wrote: On Thursday, 24 September 2015 at 08:35:40 UTC, Edwin van Leeuwen wrote: Alternatively you could use reggea to build both. I want to use dub. Simply because of code.dlang.org. Or can reggae also pull packages from there? Yes. Atila
Re: How to setup mono-D for shared libraries?
On 25/09/15 9:58 AM, Jacob wrote: On Wednesday, 23 September 2015 at 04:34:45 UTC, Rikki Cattermole wrote: On 23/09/15 8:20 AM, Jacob wrote: How do I setup mono-D for creating shared libraries and including them into other projects? When I drag the .d files to create the library from, which is not my own, I get undefined references. I have the lib files, which are a bunch of separate libs, that I want to include into one big lib. Once that's done I want to include that lib into another project. I'd rather not modify si.ini. Are there any tutorials for getting started with Mono-D? (setup, not coding) Well you could go the route of dub, which configuration files can be loaded directly into it as a project. To create the library, what do I do? 'dub init myLib' then delete app.d, and then add all the library.d files? Then what? Where do I tell it to find the .lib files without adding them to sc.ini? Do I just mess with dub.json to and add all the proper build options to get both the lib and the dependent apps working or are there other steps I'm missing? "targetType": "dynamicLibrary" http://code.dlang.org/package-format?lang=json#target-types I would also recommend looking at sub packages. http://code.dlang.org/package-format?lang=json#sub-packages That'll make things a lot easier. To have both an executable and a shared library built from the same project directory :)
Re: Dub package with C code
On Friday, 25 September 2015 at 01:36:11 UTC, Atila Neves wrote: On Thursday, 24 September 2015 at 11:38:08 UTC, Sebastiaan Koppe wrote: Or can reggae also pull packages from there? Yes. That is nice. I look at reggae once or twice. It looked like a lot of bootstrapping vs. `dub init && dub build`. And to be honest, I couldn't make immediate sense of the api. Is there any small example that builds some d code (including pulling deps)?
Re: Can I check if a value is convertible to a valid value of an enum?
On Friday, 25 September 2015 at 03:12:20 UTC, French Football wrote: ...without having to loop over the enum? writeln( test( valid_value ) ); //prints true Since `value` is known only at run time, some checks need to be performed at run time anyway. One way of doing it without iterating over all variants is to create a static hash table bool[string] valid_strings; and populate it in static constructor, then in your function you can just write if (value in valid_strings) ...
Re: Client socket sending data only one time.
On Thursday, 24 September 2015 at 14:20:39 UTC, holo wrote:
Hello
I'm trying to connect to server and send data, with such simple
client:
#!/usr/bin/rdmd
import std.stdio;
import std.socket;
import std.socketstream;
import std.process;
import std.conv;
import core.time;
void main()
{
char[1024] buffer = 0;
Socket client = new TcpSocket();
auto addrServer = new InternetAddress("localhost",
8080);
client.connect(addrServer);
while(1)
{
client.send(readln());
client.receive(buffer);
writeln(buffer);
buffer = 0;
}
}
It is working but only one time, when I'm trying to send again
(second loop of while) it's stooping on readln() but not
sending input data.
What am i missing here?
Thanks in advance for any help.
Where is the other side of this client? There must be a TCP
Server to listen connections, and create a second TCPSocket for
communication. There is only one TCPSocket in your code. A lot of
things are missing there. I would suggest you to check "C
TCPSocket example" in your favourite search engine.
Re: Maximum number of threads
On Thursday, September 24, 2015 12:38:39 Temtaime via Digitalmars-d-learn wrote: > Offtop: i think if number of threads > number of real cores, than > there's something wrong with your design. Maybe fibers suit > better ? That depends on what the threads are doing. If they're all CPU-intensive, then yeah, having more than about the number of real cores isn't going to work very well, but in many programs, a lot of the threads aren't doing much (e.g. waiting for something to happen and sitting idly in the meantime). If anything, I'd guess that it's far more common to have a lot more threads than cores if a program isn't single-threaded. I'd say that whether the number of cores matters particularly depends heavily on what your program is doing. But there are certainly cases where using fibers instead of threads makes a lot of sense. - Jonathan M Davis
Re: I can't get passing an array by reference to work anymore...
On Friday, 25 September 2015 at 02:37:22 UTC, TheGag96 wrote:
So I'm just doing a small test program here:
http://pastebin.com/UYf2n6bP
(I'm making sure I know quicksort for my algorithms class, I
know functionally this won't work as-is)
I'm on Linux, 64-bit, DMD 2.068.1, and when I try to compile
this I'm getting:
quicksort.d(18): Error: function quicksort.quickSort (ref int[]
arr) is not callable using argument types (int[])
quicksort.d(19): Error: function quicksort.quickSort (ref int[]
arr) is not callable using argument types (int[])
No matter how I attempt to define the array test, it will never
allow me to pass it by reference no matter what. I even
copy-pasted some example code from here
(https://en.wikibooks.org/wiki/D_(The_Programming_Language)/d2/Pointers,_Pass-By-Reference_and_Static_Arrays#Pass_By_Reference, bottom of the page), and it gave the same error.
What's the problem here? I SWEAR I've passed arrays by
reference before just like this. Thanks guys.
Im not sure why but..
Are you sure that you want to pass the array by ref?
In D the type int[] is like struct { size_t length; int* ptr;}
which means you are accessing through a pointer and thus changing
the data but not reassigning the array as you would with ref.
That link may well be out of date, Ali's Book
(http://ddili.org/ders/d.en/index.html) is a great resource if
you are learning.
Alternately look at the std algorithm implementation of quicksort.
Nic
Can I check if a value is convertible to a valid value of an enum?
...without having to loop over the enum?
enum SomeType : string { CHEESE = "cheese", POTATO = "potato" }
string valid_value = "cheese";
string invalid_value = "pizza";
bool test( string value ){
if( value.isConvertableToSomeType ){ // this be the magic I
seek
//do something
return true;
}
return false;
}
void main(){
writeln( test( valid_value ) ); //prints true
writeln( test( invalid_value ) ); //prints false
}
Or would I need to foreach over the enum somehow?
Re: BidirectionalRange switching direction
On Wednesday, 23 September 2015 at 03:26:29 UTC, John Colvin
wrote:
On Wednesday, 23 September 2015 at 02:10:22 UTC, Tofu Ninja
wrote:
Trying to implement a bi directional range and it is slightly
unclear what the semantics are supposed to be and just wanted
some clarification.
Are bidirectional ranges supposed to be able to support
switching direction mid iteration? Like if I do popFront
popFront popBack should that be equal to just a single
popFront? Or once you start on a direction should switching be
considered an error? Or is popFront and popBack supposed to
consume from both ends of the range and the range is empty
when they meet?
-tofu
The last one. E.g. for arrays (except narrow strings... ugh)
auto popFront(T)(ref T[] a)
{
a = a[1 .. $];
}
auto popBack(T)(ref T[] a)
{
a = a[0 .. $-1];
}
Ok cool, that's what I ended up doing.
Re: Can I check if a value is convertible to a valid value of an enum?
On Friday, 25 September 2015 at 03:12:20 UTC, French Football
wrote:
...without having to loop over the enum?
enum SomeType : string { CHEESE = "cheese", POTATO = "potato" }
string valid_value = "cheese";
string invalid_value = "pizza";
bool test( string value ){
if( value.isConvertableToSomeType ){ // this be the magic I
seek
//do something
return true;
}
return false;
}
void main(){
writeln( test( valid_value ) ); //prints true
writeln( test( invalid_value ) ); //prints false
}
Or would I need to foreach over the enum somehow?
find + EnumMembers should do the trick
if ( (EnumMembers!SomeType).canFind(value))
{
// ...
}
Re: I can't get passing an array by reference to work anymore...
On 09/24/2015 09:14 PM, Mike Parker wrote:
> I'm seeing the same error, but I haven't yet determined why.
It is because rvalues cannot be bound to 'ref' parameters:
void quickSort(ref int[] arr) {
// ...
quickSort(arr[0..wall]); // This slice is rvalue
quickSort(arr[wall+1..$]);// ditto
}
As it has already been said, there is no reason for the ref for this
function but the compilation error can be removed by making them lvalues:
auto left = arr[0..wall]; // now lvalue
quickSort(left);
auto right = arr[wall+1..$];// ditto
quickSort(right);
Then it will expose another problem with the code. ;)
Ali
Deduplicating Template Parameter List of std.variant.Algebraic
I just noticed that Algebraic doesn't deduplicate its types before construction because this compiles: import std.variant : Algebraic; auto x = Algebraic!(int, int)(5); Is this really sane?
I can't get passing an array by reference to work anymore...
So I'm just doing a small test program here: http://pastebin.com/UYf2n6bP (I'm making sure I know quicksort for my algorithms class, I know functionally this won't work as-is) I'm on Linux, 64-bit, DMD 2.068.1, and when I try to compile this I'm getting: quicksort.d(18): Error: function quicksort.quickSort (ref int[] arr) is not callable using argument types (int[]) quicksort.d(19): Error: function quicksort.quickSort (ref int[] arr) is not callable using argument types (int[]) No matter how I attempt to define the array test, it will never allow me to pass it by reference no matter what. I even copy-pasted some example code from here (https://en.wikibooks.org/wiki/D_(The_Programming_Language)/d2/Pointers,_Pass-By-Reference_and_Static_Arrays#Pass_By_Reference, bottom of the page), and it gave the same error. What's the problem here? I SWEAR I've passed arrays by reference before just like this. Thanks guys.
Re: I can't get passing an array by reference to work anymore...
On Friday, 25 September 2015 at 02:37:22 UTC, TheGag96 wrote:
What's the problem here? I SWEAR I've passed arrays by
reference before just like this. Thanks guys.
I'm seeing the same error, but I haven't yet determined why. At
any rate, this works:
```
import std.stdio;
void append(ref int[] arr, int val) {
arr ~= val;
}
void main() {
auto a1 = [10,20,30];
a1.append(40);
writeln(a1);
}
```
The compiler error aside, there's a big difference between this
function and your quicksort. This one is modifying the structure
(or metadata) of the source array. Your quicksort is only dealing
with the elements. You don't need to use ref to effect changes on
the elements of the source array. arr[1] = 2 on a function
parameter will be reflected in the source array even when ref is
absent. Only when you need to modify the length of the source
array, or cause it to point to a new memory block, would you need
to use ref.
So in your particular case, you can drop the ref from your
parameter and the compiler error will go away. However, the
function as written is producing a range violation :)
I'd still like to know what's causing the compiler error with ref
in this case, though.
pi program
import std.stdio;
import std.math;
void main()
{
float sum,pi,t;
int n=1;
sum=0;
while (n<100 )
{
t=1/( n*n);
n=n+1;
sum=sum+t;
}
writeln("value of PI= " , (sum*6)^^.5);
that is pi program as
(pi^2)/6= 1/1+ 1/4 + 1/9 + 1/16 + 1/25
but output of my program is 2.44
