Re: Implicit conversion in constructor
On Saturday, 18 July 2015 at 02:28:09 UTC, tcak wrote:
I even am not sure how in the world it allows implicit
conversion from class to struct in "fine" at all.
Given:
struct Foo {
T x;
alias x this;
}
Any time you do
Foo foo;
foo.something = whatever;
// or
foo = whatever;
// or
whatever = foo;
It first tries that code directly. If that doesn't work, it then
tries rewriting `foo` into `foo.x`:
foo.x.something = whatever;
foo.x = whatever;
whatever = foo.x;
And if that compiles, you're all set, that code gets generated.
The OP's situation is just case #2 here. The compiler is taking
the illegal `thing = new Foo;` and rewriting it into the legal
`thing.foo = new Foo;` automatically via alias this.
Re: Implicit conversion in constructor
On Saturday, 18 July 2015 at 02:23:26 UTC, rcorre wrote:
Is there any reason why implicit conversion from Foo to Thing
is permitted in a regular method but not in a constructor?
In the constructor, you are supposed to be constructing things,
so the first "assignment" of structs is actually a constructor
call. D does not support implicit construction (kinda sadly, but
it doesn't).
In the other methods, it calls opAssign instead, since the struct
already exists. So this is the difference between:
Thing thing = new Foo(); // in the ctor, this line in main
wouldn't work either with the same error
and
thing = new Foo(); // in the other method, this line in main does
work
Try adding `void opAssign(T)(T t) { static assert(0); }` to your
struct and recompile. You'll see it throws on the method. Then
change that `opAssign` to `this`, so it becomes a constructor.
Then you'll see it is called in the class constructor.
Moreover, note that this only applies to the *first* assignment
of the struct. If you copy/paste that line in the constructor
again right under it, you'll see the compiler only throws the
error once. The first one is a construction. The second one is a
standard assignment again.
Put those two lines in a runtime branch: `if(something) thing =
new Foo(); else thing = new Foo();` and notice how the compiler
throws two errors again.
The first assignment in any branch of a constructor is a
construction! The next one is an assignment.
So the rule is slightly complex (and the implementation may be
buggy, though it seems good to me now), but it is intentional.
The reason for this goes beyond just that constructors are
supposed to be constructing. It also is relevant for `immutable`
members - these are allowed to be constructed, but not modified,
so if the class constructor didn't treat those as constructions,
it would be impossible to set them up with runtime data.
And it is also important for `@disable this()` struct members,
which must be constructed explicitly. If the first assignment in
a ctor didn't count for that, you couldn't have them in a class
at all.
Re: Are Lua tables possible to do with D?
On Thursday, 16 July 2015 at 07:20:16 UTC, Fusxfaranto wrote:
An associative array of Variant[string] ought to do the job
well enough.
http://dlang.org/phobos/std_variant.html
For extra fun, you can implement the '.' style syntax pretty
easily:
---
import std.variant;
struct LuaTable {
Variant[string] _table;
alias _table this;
auto opDispatch(string s)() {
return _table[s];
}
void opDispatch(string s, T)(T val) {
_table[s] = Variant(val);
}
}
unittest {
LuaTable table;
table.foo = 5;
table.bar = "s";
assert(table.foo == 5);
assert(table.bar == "s");
}
---
Re: Implicit conversion in constructor
On Saturday, 18 July 2015 at 02:28:09 UTC, tcak wrote: I even am not sure how in the world it allows implicit conversion from class to struct in "fine" at all. The 'alias this' in the struct permits implicit conversion. I _think_ that is intended behavior, though I admit I'm not actually sure now. I've been taking it for granted for awhile...
Re: Implicit conversion in constructor
On Saturday, 18 July 2015 at 02:23:26 UTC, rcorre wrote:
Is there any reason why implicit conversion from Foo to Thing
is permitted in a regular method but not in a constructor?
Trying to figure out whether this is a bug or some sort of
constructor-specific safety precaution.
struct Thing {
Foo foo;
alias foo this;
}
class Foo { }
class Bar {
Thing thing;
void fine() {
thing = new Foo(); // ok
}
this() {
thing = new Foo(); // nope!
}
}
I even am not sure how in the world it allows implicit conversion
from class to struct in "fine" at all.
Implicit conversion in constructor
Is there any reason why implicit conversion from Foo to Thing is
permitted in a regular method but not in a constructor?
Trying to figure out whether this is a bug or some sort of
constructor-specific safety precaution.
struct Thing {
Foo foo;
alias foo this;
}
class Foo { }
class Bar {
Thing thing;
void fine() {
thing = new Foo(); // ok
}
this() {
thing = new Foo(); // nope!
}
}
Re: Virtual value types during compile-time for static type safety, static optimizations and function overloading.
On Friday, 17 July 2015 at 23:44:25 UTC, Tamas wrote: I used DMD, BTW. what compile flags?
Re: Using executeShell in multiple thread causes access violation error
On Monday, 13 July 2015 at 09:46:26 UTC, Minas Mina wrote: I have written a script that visits all directories in the current directory and executes a command. In my case, "git pull". When running the script serially, everything is fine. All git repositories are pulled. But I'd like to pull multiple repositories in parallel to speed things up. So I've changed my loop from foreach(entry; dirs) to foreach(entry; parallel(dirs)) After a while that the program is running I get: std.exception.ErrnoException@std\stdio.d(638): Could not close file `HANDLE(C0)' (No error) 0x00411E5C 0x0040B8AB 0x0040A146 0x00402288 0x00403A99 0x00413B95 0x004095FC 0x00439AA0 0x770992B2 in RtlInitializeExceptionChain 0x77099285 in RtlInitializeExceptionChain object.Error@(0): Access Violation 0x00439429 0x0043A277 0x00411ECD 0x763A9B2C in GetFileAttributesW Here is the code: http://pastebin.com/Tk0TBGxs Probably this is a Windows only problem. I tried the following code on my Linux machine and I didn't get any exception like yours: https://gist.github.com/ZombineDev/e1e48a18a22d4fc85e8d Can you run my code just so we can confirm that the problem is in the Windows implementation and not in your code? Also what compiler version are you using? If you don't get exception while using your code, it would be better if you could show me a complete code snippet so the issue can be reproduced.
Re: Getting Nth Row and Column from MatrixView, Scid library
On Friday, 17 July 2015 at 22:05:45 UTC, kerdemdemir wrote: Sad times with linear algebra libraries for me, Since I can't get rows and columns easily with Scid, It seems not flexible for me. And also there are other issues for example I can't set matrix to row or column major. I begin to check alternatives first I begin to investigate Dlib. D lib matrixes are unfortunately static once created their size can't be expanded and must be square matrix. This restrictions seem too much to me . The best alternative seems to me scid fork of "Cristi Cobzarenco" link: https://github.com/cristicbz/scid. It has the basic features I need. But it seems last commit made 3 years ago. I couldn't compile it. I am getting error: scid\internal\regionallocator.d(364): Error: safe function 'scid.internal.region allocator.threadLocalSegmentSize' cannot call system function 'scid.internal.reg ionallocator.RegionAllocatorException.this' Error building library Any advice about another lib or fix compile error will be welcome. No idea if it will help with what you need, and the documentation is still a work in progress, but this is my library for embedding D in R (similar to Rcpp): https://bitbucket.org/bachmeil/dmdinline2/overview It does have an easy way to work with rows and columns.
Re: Virtual value types during compile-time for static type safety, static optimizations and function overloading.
On Friday, 17 July 2015 at 21:20:41 UTC, Tamas wrote:
Although this code is fully operational, presents nice api and
compile-time optimizations, the extra Struct wrapper is not
without runtime penalty.
Is there a solution that results the same static optimizations,
but has no runtime penalty, i.e. the functions just operates
with ints? (At least when compiled)
Thanks, Tamas
Hi, I don't see the runtime penalities you talk about.
I've defined these alias:
---
alias abs1 = abs!int;
alias abs2 = abs!Positive;
alias isqrt1 = isqrt!int;
alias isqrt2 = isqrt!Positive;
---
and the asm produced for the `Positive` type is clearly faster:
;--- abs1 ---
00402074h enter 000Ch, 00h
00402078h test eax, eax
0040207Ah js 00402081h
0040207Ch mov dword ptr [ebp-0Ch], eax
0040207Fh leave
00402080h ret
00402081h neg eax
00402083h mov dword ptr [ebp-08h], eax
00402086h leave
00402087h ret
;
;--- abs2 (Positive)---
00402088h enter 0004h, 00h
0040208Ch leave
0040208Dh ret
;
;--- isqrt1 ---
00402090h enter 0008h, 00h
00402094h test eax, eax
00402096h jns 004020CFh
00402098h mov ecx, 00454D60h
0040209Dh push ecx
0040209Eh call 00403410h
004020A3h add esp, 04h
004020A6h push dword ptr [004540A4h]
004020ACh push dword ptr [004540A0h]
004020B2h push dword ptr [004540E4h]
004020B8h push dword ptr [004540E0h]
004020BEh push 001Bh
004020C0h push h
004020C2h call 004035C0h
004020C7h push eax
004020C8h call 00403400h
004020CDh jmp 004020E6h
004020CFh call 0040247Ch
004020D4h fsqrt
004020D6h sub esp, 04h
004020D9h fstp dword ptr [esp]
004020DCh call 00402494h
004020E1h mov dword ptr [ebp-08h], eax
004020E4h leave
004020E5h ret
004020E6h leave
004020E7h ret
;
;--- isqrt2 (Positive)---
004020E8h enter 0008h, 00h
004020ECh call 00402560h
004020F1h fsqrt
004020F3h sub esp, 04h
004020F6h fstp dword ptr [esp]
004020F9h call 00402494h
004020FEh mov dword ptr [ebp-08h], eax
00402101h leave
00402102h ret
;
(dmd win32 bit, -w -wi).
Also note that i've tweaked the code to get rid of a few warnings:
---
Positive abs(T)(T n) {
static if (is(T == Positive)) {
return n;
}
else
{
if (n >= 0) return Positive(n);
else return Positive(-n);
}
}
Positive isqrt(T)(T x) {
static if (is(T == Positive)) {
return Positive(sqrt(x.to!float).to!int);
}
else
{
if (x<0)
throw new Exception("no root for negative numbers");
else return Positive(sqrt(x.to!float).to!int);
}
}
---
Re: Virtual value types during compile-time for static type safety, static optimizations and function overloading.
On Friday, 17 July 2015 at 23:16:51 UTC, ZombineDev wrote: On Friday, 17 July 2015 at 23:15:31 UTC, ZombineDev wrote: On Friday, 17 July 2015 at 21:20:41 UTC, Tamas wrote: Is there a solution that results the same static optimizations, but has no runtime penalty, i.e. the functions just operates with ints? (At least when compiled) Did you try looking at assembly generated by GDC or LDC with full optimizations? For example GDC does quite better than DMD for the proposed SafeInt type: https://github.com/D-Programming-Language/phobos/pull/3389#issuecomment-119005595 Also, see the table at the bottom of this comment: https://github.com/D-Programming-Language/phobos/pull/3389#issuecomment-117450524 Thanks for the pointers! My first priority a performant library, secondary is a nice api, 3rd is a nice implementation. So that kind of rules put Amy degradation compared to ints. I used DMD, BTW. I see no reason for the necessity of performance degradation. Essentially I just want to assign a similar qualifyer like const or immutable. They are checked and used at compile time, but erased for runtime. Same here.
Re: Virtual value types during compile-time for static type safety, static optimizations and function overloading.
On Friday, 17 July 2015 at 23:15:31 UTC, ZombineDev wrote: On Friday, 17 July 2015 at 21:20:41 UTC, Tamas wrote: Is there a solution that results the same static optimizations, but has no runtime penalty, i.e. the functions just operates with ints? (At least when compiled) Did you try looking at assembly generated by GDC or LDC with full optimizations? For example GDC does quite better than DMD for the proposed SafeInt type: https://github.com/D-Programming-Language/phobos/pull/3389#issuecomment-119005595 Also, see the table at the bottom of this comment: https://github.com/D-Programming-Language/phobos/pull/3389#issuecomment-117450524
Re: Virtual value types during compile-time for static type safety, static optimizations and function overloading.
On Friday, 17 July 2015 at 21:20:41 UTC, Tamas wrote: Is there a solution that results the same static optimizations, but has no runtime penalty, i.e. the functions just operates with ints? (At least when compiled) Did you try looking at assembly generated by GDC or LDC with full optimizations? For example GDC does quite better than DMD for the proposed SafeInt type: https://github.com/D-Programming-Language/phobos/pull/3389#issuecomment-119005595
Re: Using executeShell in multiple thread causes access violation error
bump
Re: Getting Nth Row and Column from MatrixView, Scid library
Sad times with linear algebra libraries for me, Since I can't get rows and columns easily with Scid, It seems not flexible for me. And also there are other issues for example I can't set matrix to row or column major. I begin to check alternatives first I begin to investigate Dlib. D lib matrixes are unfortunately static once created their size can't be expanded and must be square matrix. This restrictions seem too much to me . The best alternative seems to me scid fork of "Cristi Cobzarenco" link: https://github.com/cristicbz/scid. It has the basic features I need. But it seems last commit made 3 years ago. I couldn't compile it. I am getting error: scid\internal\regionallocator.d(364): Error: safe function 'scid.internal.region allocator.threadLocalSegmentSize' cannot call system function 'scid.internal.reg ionallocator.RegionAllocatorException.this' Error building library Any advice about another lib or fix compile error will be welcome.
Re: Working functionally with third party libraries
On Friday, 17 July 2015 at 17:56:51 UTC, sigod wrote: On Friday, 17 July 2015 at 15:41:22 UTC, ZombineDev wrote: eager approach, since it's more straightforward. What makes you think it's always more straightforward? Sometimes (like in this case with MongoDB) you cannot write eager approach without first writing lazy one. Well I just wrote without properly looking up what MongoDB does. I thought collection.find() returned the first n elements, not a iterator (cursor in MongoDB's terms) and that it would be additional work split those n elements. Anyway, thanks for the correction, now I am bit more educated ;)
Virtual value types during compile-time for static type safety, static optimizations and function overloading.
I got inspired by Andrei's "Generic Programming Must Go" talk:
https://www.youtube.com/watch?v=mCrVYYlFTrA
I.e. writing functions with static if-s, based on what we know
about the input.
So the question is how to annotate the input variables?
Adam showed an excellent solution for this, by wrapping the value
into a struct, and using alias:
http://stackoverflow.com/questions/31442059/virtual-static-value-types
Unfortunately, it's not without runtime penalty. I have checked
this idea with ints, against the generated asm.dlang.org code.
Unfortunately the struct wrapper results in longer asm code. In
theory such run-time penalty is not necessary, as everything is
available compile-time.
To understand my use-case, here is an example "math library" that
skips certain validations or computations altogether, whether
some properties of the input can be inferred from how the value
was produced:
import std.math : sqrt;
import std.conv;
struct Positive {
int num;
alias num this;
}
Positive abs(T)(T n) {
static if (is(T == Positive)) {
return n;
}
if (n >= 0) return Positive(n);
return Positive(-n);
}
Positive isqrt(T)(T x) {
static if (is(T == Positive)) {
return Positive(sqrt(x.to!float).to!int);
}
if (x<0) {
throw new Exception("no root for negative numbers");
}
return Positive(sqrt(x.to!float).to!int);
}
unittest {
assert(abs(-4) == 4); // full abs runs
assert(isqrt(4).abs() == 2); // full isqrt runs, abs returns n
immediately.
assert(abs(-4).isqrt() == 2); // full abs runs, isqrt return
immediately, skipping validation;
}
Although this code is fully operational, presents nice api and
compile-time optimizations, the extra Struct wrapper is not
without runtime penalty.
Is there a solution that results the same static optimizations,
but has no runtime penalty, i.e. the functions just operates with
ints? (At least when compiled)
Thanks, Tamas
Can you add a remote repository to DUB?
All I can find is add-local. Thanks!
Re: How to convert byte array to float
On Friday, July 17, 2015 18:43:26 DLangLearner via Digitalmars-d-learn wrote: > Excuse me for my trivial question, but I'd like to know how to > convert byte array to float? What I could think of are > cast(float)(byte[]) and to!float(byte[]) but they do not work for > me. Thanks! You could use std.bitmanip.peek or std.bitmanip.read - though you do need to make sure that you're telling it the right endianness, depending on how the array of bytes was generated. - Jonathan M Davis
Re: How to convert byte array to float
On Friday, 17 July 2015 at 18:58:33 UTC, byron wrote: On Friday, 17 July 2015 at 18:53:24 UTC, byron wrote: On Friday, 17 July 2015 at 18:43:27 UTC, DLangLearner wrote: Excuse me for my trivial question, but I'd like to know how to convert byte array to float? What I could think of are cast(float)(byte[]) and to!float(byte[]) but they do not work for me. Thanks! You want to include [] in the cast so: byte[] b = [1, 2, 3, 4] byte[] f = cast(float[])b; writeln(b); writeln(f); You can even cast on a slice: byte[] b = [1, 2, 3, 4, 5, 6, 7, 8] byte[] f = cast(float[])b[4..8]; Ah I miss read, if you want as a float, not a float array you can do: byte[] b = [1, 2, 3, 4]; float f = *cast(float*)b.ptr; not sure if there is a better way thanks for quick reply, i'll plug above lines into my codes.
Re: How to convert byte array to float
On Friday, 17 July 2015 at 19:03:46 UTC, Jacob Carlborg wrote:
On 2015-07-17 20:58, byron wrote:
Ah I miss read, if you want as a float, not a float array you
can do:
byte[] b = [1, 2, 3, 4];
float f = *cast(float*)b.ptr;
not sure if there is a better way
I think a union can be used as well, not sure if it's better
though.
not a bad idea.
testing on asm.dlang.org both reduce to the same assembly
(-release -inline -O)
float pointerTest(inout byte[4] b) {
return *cast(float*)b.ptr;
}
float unionTest(inout byte[4] b) {
union U {
byte[4] b;
float f;
}
return U(b).f;
}
Re: Template function that accept strings and array of strings
On 2015-07-17 19:25, badlink wrote: My fault, I didn't test the variadic function enough and jumped to conclusion. It actually works well http://pastebin.com/R4EHuBLh Cool :) Sometimes D developers think templates will be needed to solve everything. -- /Jacob Carlborg
Re: Environment variable for application storage under OSX ?
On 2015-07-17 15:27, anonymous wrote:
Ok so my sample can be rewritten
static this() {
version(Win32) p = environment.get("APPDATA");
version(linux) p = "/home/" ~ environment.get("USER");
version(OSX) p = environment.get("HOME") ~ /Library/Application
Support/;
}
---
Ideally you should hard code the values like this. BTW, why don't you
use the HOME environment variable on Linux.
I really wish it could be possible to buy and setup OSX on any
hardware...I will never buy a mac just to test the portability of a
couple of projects 1 hour per week...
It's possible to run OS X on non-Apple computers, including virtual
machines. But this is not the place to discuss this.
--
/Jacob Carlborg
Re: How to convert byte array to float
On 2015-07-17 20:58, byron wrote: Ah I miss read, if you want as a float, not a float array you can do: byte[] b = [1, 2, 3, 4]; float f = *cast(float*)b.ptr; not sure if there is a better way I think a union can be used as well, not sure if it's better though. -- /Jacob Carlborg
Re: How to convert byte array to float
On Friday, 17 July 2015 at 18:53:24 UTC, byron wrote: On Friday, 17 July 2015 at 18:43:27 UTC, DLangLearner wrote: Excuse me for my trivial question, but I'd like to know how to convert byte array to float? What I could think of are cast(float)(byte[]) and to!float(byte[]) but they do not work for me. Thanks! You want to include [] in the cast so: byte[] b = [1, 2, 3, 4] byte[] f = cast(float[])b; writeln(b); writeln(f); You can even cast on a slice: byte[] b = [1, 2, 3, 4, 5, 6, 7, 8] byte[] f = cast(float[])b[4..8]; Ah I miss read, if you want as a float, not a float array you can do: byte[] b = [1, 2, 3, 4]; float f = *cast(float*)b.ptr; not sure if there is a better way
Re: LNK2019 error from using a function pointer to core.bitop functions?
On Friday, 17 July 2015 at 15:49:46 UTC, Roland Hadinger wrote:
On Friday, 17 July 2015 at 15:47:39 UTC, Roland Hadinger wrote:
Otherwise, I'd use templates and an alias. Maybe this will
result in faster code:
bool opIndexAssign(bool value, size_t[2] inds)
{
void impl(bool b)(size_t[2] inds)
{
static if(b)
alias btx = bts;
else
alias btx = btr;
// code from opIndexAssign goes here...
// for (size_t i = startBitInd; ...
}
if( value )
impl!true(inds);
else
impl!false(inds);
return value; // oops
}
Roland, both of your solutions work perfectly. Thank you.
You brought up the issue of performance. Performance may be an
issue for certain use-cases when the function is called many
times and the values of inds[1] - inds[0] is small (e.g less than
257). In these cases at least half the work in the function will
be done with bts/btr. However, for larger ranges there is an
optimization (not shown) that eliminates the need to call bts/btr
in the middle region of the range.
Why do you think the second solution would be faster than the
first? And do you also think that the rolled out version
replicating the code in the "if" and "else" blocks replacing bts
with btr would be even faster since it eliminates the need for
any additional function call? I guess I'll have to profile all
three versions when my program matures enough be used with a
"big" data example.
Sorry for all the questions. I really appreciate your help.
Best, Matt
Re: How to convert byte array to float
On Friday, 17 July 2015 at 18:43:27 UTC, DLangLearner wrote: Excuse me for my trivial question, but I'd like to know how to convert byte array to float? What I could think of are cast(float)(byte[]) and to!float(byte[]) but they do not work for me. Thanks! You want to include [] in the cast so: byte[] b = [1, 2, 3, 4] byte[] f = cast(float[])b; writeln(b); writeln(f); You can even cast on a slice: byte[] b = [1, 2, 3, 4, 5, 6, 7, 8] byte[] f = cast(float[])b[4..8];
How to convert byte array to float
Excuse me for my trivial question, but I'd like to know how to convert byte array to float? What I could think of are cast(float)(byte[]) and to!float(byte[]) but they do not work for me. Thanks!
Re: Comparison of struct with Nullable member
On Friday, 17 July 2015 at 12:18:56 UTC, TC wrote:
Hello,
I came around a strange behavior and I'm not sure if it is a
bug or feature.
import std.typecons : Nullable;
struct Foo
{
string bar;
Nullable!int baz;
}
auto a = Foo("bb");
auto b = Foo("bb");
assert(a == b);
This ends up with: Called `get' on null Nullable!int
But if I change bar to be an int for example, than it passes ok.
I would expect this to pass ok.
Tested on dmd 2.067.1 win64
Bug. I reported a reduced version as
.
Re: Working functionally with third party libraries
On Friday, 17 July 2015 at 15:41:22 UTC, ZombineDev wrote: eager approach, since it's more straightforward. What makes you think it's always more straightforward? Sometimes (like in this case with MongoDB) you cannot write eager approach without first writing lazy one.
Re: Template function that accept strings and array of strings
On Friday, 17 July 2015 at 12:58:58 UTC, Jacob Carlborg wrote: I don't think I really understand how you want to use/call the function. Could you give an example with all the different types you want to call the function? My fault, I didn't test the variadic function enough and jumped to conclusion. It actually works well http://pastebin.com/R4EHuBLh
Re: How to use core.thread.Thread
On Friday, 17 July 2015 at 14:14:41 UTC, byron wrote:
Since I have yet to use or see anyone use shared in a useful
way I avoid it.
It's one way to avoid it. So, you mean you always use send/receive
when you need threading?
I did small test to know the memory layout.
import core.atomic;
int foo;
shared int sfoo;
class DerivedThread : Thread {
int count;
shared int scount;
this() {
super(&run);
}
private void run() {
inc();
writefln("at thread: foo=%s, &foo=%s, sfoo=%s, &sfoo=%s",
foo, &foo, sfoo, &sfoo);
writefln("at thread: count=%s, &count=%s, scount=%s,
&scount=%s", count, &count, scount, &scount);
}
void inc() {
++foo;
atomicOp!"+="(sfoo, 1);
++count;
atomicOp!"+="(scount, 1);
}
}
void main() {
auto thr = new DerivedThread();
thr.start();
thr.inc();
thr.join();
writefln(" at main: foo=%s, &foo=%s, sfoo=%s, &sfoo=%s",
foo, &foo, sfoo, &sfoo);
writefln(" at main: count=%s, &count=%s, scount=%s,
&scount=%s", thr.count, &thr.count, thr.scount, &thr.scount);
}
at thread: foo=1, &foo=A33580, sfoo=2, &sfoo=5541E4
at thread: count=2, &count=240178, scount=2, &scount=24017C
at main: foo=1, &foo=984B28, sfoo=2, &sfoo=5541E4
at main: count=2, &count=240178, scount=2, &scount=24017C
That means Thread object "thr" is always shared while
global foo is not shared because it has different memory location.
In my understanding, shared is not only checking something at
compile time,
but also it affects on the memory layout.
Aki.
Re: Comparison of struct with Nullable member
On Friday, 17 July 2015 at 15:52:45 UTC, TC wrote:
On Friday, 17 July 2015 at 15:30:42 UTC, Meta wrote:
https://issues.dlang.org/show_bug.cgi?id=14804
I'll probably be able to submit a PR for this sometime in the
next few days.
Thanks.
What I don't get is why this one works ok?
import std.typecons : Nullable;
struct Foo
{
int bar;
Nullable!int baz;
}
auto a = Foo(1);
auto b = Foo(1);
assert(a == b);
This may be because if your struct only contains primitive
values, the compiler will just do a memcmp to determine equality.
Don't quote me on that though.
Also is there some "nicer" way to init the struct with nullable
member with default constructor?
Now I'm using Foo(1, Nullable!int(2)) but just Foo(1, 2) would
be much nicer.
Same with calling functions with nullable params.
You can defined a custom constructor in Foo which will construct
the Nullable.
struct Foo
{
this(int n1, int n2)
{
bar = n1;
baz = n2;
}
//...
}
Re: LNK2019 error from using a function pointer to core.bitop functions?
On Thursday, 16 July 2015 at 03:24:54 UTC, Matthew Gamble wrote:
This member function of my struct uses a function pointer btx.
When the line declaring the function pointer is present I get a
LNK2019 error: unresolved external symbol.
Just guessing, probably because bts and btr are intrinsics?
If performance is not that important, you can always do this at
the start of your opIndexAssign method:
static int bts(size_t* p, size_t bitnum) { return .bts(p,
bitnum); }
static int btr(size_t* p, size_t bitnum) { return .btr(p,
bitnum); }
int function(size_t*, size_t) btx = (value) ? &bts : &btr;
Otherwise, I'd use templates and an alias. Maybe this will result
in faster code:
bool opIndexAssign(bool value, size_t[2] inds)
{
void impl(bool b)(size_t[2] inds)
{
static if(b)
alias btx = bts;
else
alias btx = btr;
// code from opIndexAssign goes here...
// for (size_t i = startBitInd; ...
}
if( value )
impl!true(inds);
else
impl!false(inds);
}
Re: Comparison of struct with Nullable member
On Friday, 17 July 2015 at 15:30:42 UTC, Meta wrote:
https://issues.dlang.org/show_bug.cgi?id=14804
I'll probably be able to submit a PR for this sometime in the
next few days.
Thanks.
What I don't get is why this one works ok?
import std.typecons : Nullable;
struct Foo
{
int bar;
Nullable!int baz;
}
auto a = Foo(1);
auto b = Foo(1);
assert(a == b);
Also is there some "nicer" way to init the struct with nullable
member with default constructor?
Now I'm using Foo(1, Nullable!int(2)) but just Foo(1, 2) would be
much nicer.
Same with calling functions with nullable params.
Re: Working functionally with third party libraries
On Friday, 17 July 2015 at 15:41:22 UTC, ZombineDev wrote: I'm almost certain that the D database driver returns eagerly all the results that you've requested. The lazy stuff should happen when you start doing range operations after the results are returned from the database. It's not impossible to lazily query the database, but I think that the developers have chosen the eager approach, since it's more straightforward. Discard this. I didn't read the previous comments.
Re: LNK2019 error from using a function pointer to core.bitop functions?
On Friday, 17 July 2015 at 15:47:39 UTC, Roland Hadinger wrote:
Otherwise, I'd use templates and an alias. Maybe this will
result in faster code:
bool opIndexAssign(bool value, size_t[2] inds)
{
void impl(bool b)(size_t[2] inds)
{
static if(b)
alias btx = bts;
else
alias btx = btr;
// code from opIndexAssign goes here...
// for (size_t i = startBitInd; ...
}
if( value )
impl!true(inds);
else
impl!false(inds);
return value; // oops
}
Re: Working functionally with third party libraries
On Friday, 17 July 2015 at 09:07:29 UTC, Jarl André Hübenthal
wrote:
Thanks. Its a lot more cleaner and syntactically readable
having .array at the end. But about laziness the same applies
to clojure and scala. In clojure you must force evaluate the
list, in scala you must to mostly the same as in D, put a
toList or something at the end. Or loop it. But its pretty nice
to know that there is laziness in D, but when I query mongo I
expect all docs to be retrieved, since there are no paging in
the underlying queries? Thus, having a lazy functionality on
top of non lazy db queries seem a bit off dont you think?
I'm almost certain that the D database driver returns eagerly all
the results that you've requested. The lazy stuff should happen
when you start doing range operations after the results are
returned from the database. It's not impossible to lazily query
the database, but I think that the developers have chosen the
eager approach, since it's more straightforward.
Currently, in D most of the laziness is a convention, rather than
something directly built into the language. There are many
features that enable (indirectly) effective and easy to use lazy
algorithms, but these features are have many other uses
(templates, auto type deduction, compile-time reflection, etc.).
The only two direct features are:
1) foreach can iterate over ranges (objects of structs or classes
for which isInputRange is true. Here's an example:
import std.algorithm.iteration : map, filter;
foreach (name; persons.filter!(p => p.age > 18).map!(p => p.name))
writeln(name);
import std.range.primitives : isInputRange;
static assert (
isInputRange!(
typeof(
persons.filter!(p => p.age > 18).map!(p => p.name)
)
) == true
);
See http://dlang.org/phobos/std_range_primitives.html#isInputRange
2) The lazy keyword - when you annotate function parameters with
lazy they are evaluated not at the caller site, but only when
needed like in other more traditional functional languages. For
example:
void calculate(int[] numbers)
{
import std.format : format;
// ...
logErrorIf(numbers[3] < 5,
format("Expected value < 5, but got %s !", numbers[3]));
// ^~~~ this is only evaluated
// ...
}
void logErrorIf(bool condition, lazy string error_message)
{
if (condition)
writeln(message);
// ^~~~ here, if the condition is true
}
( In D string is just an alias to immutable(char)[], so the above
signature is identical to this:
void logErrorIf(bool condition, lazy immutable(char)[]
error_message) )
You can think of lazy parameters as implicit lambdas that return
the expression passed as argument only when called.
Here you can learn more about the lazy keyword
http://dlang.org/lazy-evaluation.html
Even though we have 'lazy' built into the language, most of the
lazy algorithms do not use it. I just made a quick search through
druntime and phobos for 'lazy' and 'range' (don't how correct it
was - I admit I'm a unix noob) and here's what I got:
// (I have DMD v2.067.1 installed)
// lazy at the head of the function parameter list or in the tail
$ find /usr/include/dmd/ -name '*.d' -exec cat {} \; | grep -c
'(lazy \|, lazy '
74
// just containing lazy
$ find /usr/include/dmd/ -name '*.d' -exec cat {} \; | grep -c
'lazy'
138
// just containing range
$ find /usr/include/dmd/ -name '*.d' -exec cat {} \; | grep -c
'range'
3548
I think that this because ranges are a more generic, flexible and
powerful abstraction, and are more efficient maybe because
they're easier to optimize to simple loops (eg. I've seen that
the ldc compiler handles them very well).
'lazy' is still useful but generally I have seen it used for more
simpler stuff (like the above 'lazy' example), and not for
propagating state through range pipelines (or more simply -
function chaining).
So you'll see both functions that are lazy and functions that are
not throughout Phobos (and most use ranges, as you can see from
the results).
Generally you can distinguish range functions from others by
their signatures. Since most ranges in D are templated structs
and not classes inheriting some interface
(though there some, see
http://dlang.org/phobos/std_range_interfaces#InputRange),
functions that operate on ranges are templated at least on one
range type:
// Check if the function 'fun' is really a predicate
enum isUnaryPredicate(alias fun, T) =
is( typeof( fun(T.init) ) : bool);
import std.range.primitives: isInputRange, ElementType;
// templated on predicate and range type
//v ~~v~~
auto filter1(alias predicate, Range)(Range range)
if (isInputRange!Range && // <- some template
isUnaryPredicate!(predicate, ElementType!Range))
// ^~ constraints
{
return ...
}
// Even if you can't look at the function body, you
// can guess that it can't be lazy becau
Re: Comparison of struct with Nullable member
On Friday, 17 July 2015 at 12:18:56 UTC, TC wrote:
Hello,
I came around a strange behavior and I'm not sure if it is a
bug or feature.
import std.typecons : Nullable;
struct Foo
{
string bar;
Nullable!int baz;
}
auto a = Foo("bb");
auto b = Foo("bb");
assert(a == b);
This ends up with: Called `get' on null Nullable!int
But if I change bar to be an int for example, than it passes ok.
I would expect this to pass ok.
Tested on dmd 2.067.1 win64
https://issues.dlang.org/show_bug.cgi?id=14804
I'll probably be able to submit a PR for this sometime in the
next few days.
Re: How to use core.thread.Thread
On Friday, 17 July 2015 at 07:56:48 UTC, aki wrote:
On Thursday, 16 July 2015 at 09:17:47 UTC, Daniel Kozák wrote:
class DerivedThread : Thread {
shared int count = 0;
}
I thought shared is only for whole of the object.
auto thr = new DerivedThread();
Here, "thr" is not shared but it's member thr.count is shared?
But if it's not shared, thr object referred by main thread and
"this" reference of DerivedThread.run() are different?
What happen if there are both shared and unshared member exists?
class DerivedThread : Thread {
shared int count = 0;
int foo = 0;
}
Umm. I can't imagine what's the memory layout of this object.
Since I have yet to use or see anyone use shared in a useful way
I avoid it. But I normally think of it like const (not
immutable). Shared wont change the memory layout (last time I
checked) its purpose is meant to help you write correct threaded
code, ie make sure you synchronize access to it, its not synced
for you. You should read the chapter from Andrie's book.
There is also a lot of good stuff in the std lib the helps avoid
doing things manually.
Re: Infinite range of nullable elements
On Friday, 17 July 2015 at 12:44:57 UTC, anonymous wrote:
The building blocks are there. You're `map`ping the original
range to `Nullable`, and then you're `chain`ing an infinite
range (`cycle`) of nulls behind.
import std.range: isInputRange;
auto cushion(R)(R r)
if (isInputRange!R)
{
import std.algorithm: map;
import std.range: chain, cycle, ElementType, only;
import std.typecons: Nullable;
alias E = ElementType!R;
alias NE = Nullable!E;
return chain(r.map!NE, NE().only.cycle);
}
Nice! I didn't think of using 'chain'.
Re: Comparison of struct with Nullable member
On Friday, 17 July 2015 at 12:18:56 UTC, TC wrote:
Hello,
I came around a strange behavior and I'm not sure if it is a
bug or feature.
import std.typecons : Nullable;
struct Foo
{
string bar;
Nullable!int baz;
}
auto a = Foo("bb");
auto b = Foo("bb");
assert(a == b);
This ends up with: Called `get' on null Nullable!int
But if I change bar to be an int for example, than it passes ok.
I would expect this to pass ok.
Tested on dmd 2.067.1 win64
what is happening is the complier generated default opEquals is
accessing the payload for Nullable!T without checking for null
(which as you've written `Foo("bb")` this constructs a and b as
`Foo("bb",(Nullable!int).init)` i.e. in the null state)
why nullables don't automatically check for null when comparing
for equality idk.
you can make this work by defining your own opEquals that
explicitly checks for nulls.
Re: Environment variable for application storage under OSX ?
On Friday, 17 July 2015 at 07:54:43 UTC, FreeSlave wrote:
On Friday, 17 July 2015 at 07:33:43 UTC, Anonymous wrote:
On Friday, 17 July 2015 at 07:14:24 UTC, FreeSlave wrote:
On Thursday, 16 July 2015 at 21:12:05 UTC, anonymous wrote:
I have the following code, working under Win and Linux:
---
import std.process: environment;
immutable string p;
static this() {
version(Win32) p = environment.get("APPDATA");
version(linux) p = "/home/" ~ environment.get("USER");
version(OSX) p = "?";
}
---
what would be the OSX equivalent (to get the path where the
applications data are commonmly stored)?
Hello. You may take a look at this library
https://github.com/MyLittleRobo/standardpaths
OSX version uses Carbon though. You may want to use Cocoa API
(which is newer), but it's Objective-C.
Also you may consider standard path for data storage without
using any api or spec. It's usually $HOME/Library/Application
Support/ on OSX.
So for a software named 'SuperDownloader2015' it would be
$HOME/Library/Application Support/SuperDownloader2015
right ?
so it's not user-specific and it's writable for the current
user ?
sorry but it looks a bit strange, anyone can confirm ?
It is user specific obviously since it's in user home.
Can you elaborate on what do you want exactly?
From Windows and Linux examples you provided I assumed you need
user-specific paths (APPDATA is defined per user on Windows).
System-wide application data path is different.
Ok so my sample can be rewritten
static this() {
version(Win32) p = environment.get("APPDATA");
version(linux) p = "/home/" ~ environment.get("USER");
version(OSX) p = environment.get("HOME") ~
/Library/Application Support/;
}
---
I really wish it could be possible to buy and setup OSX on any
hardware...I will never buy a mac just to test the portability of
a couple of projects 1 hour per week...
Anyway thx all for your answers.
Re: Infinite range of nullable elements
On Friday, 17 July 2015 at 10:19:22 UTC, Márcio Martins wrote: On Friday, 17 July 2015 at 07:42:09 UTC, Roland Hadinger wrote: At this moment I'm tempted to implement a function taking a range of elements E and returning an infinite range of Nullable!E. [...] Wouldn't it still require the algorithms to check if an element isNull()? Naturally. But this check can be done further down the function chain, so all the functions before will see an infinite range. I'm currently writing a lexer (big loop with two levels of switch statements inside) that needs to some looking ahead in multiple states. Normally, each of those lookaheads would require a check for "end of input". I want to avoid this because of the large number of states.
Re: Environment variable for application storage under OSX ?
On 2015-07-17 09:14, FreeSlave wrote: Hello. You may take a look at this library https://github.com/MyLittleRobo/standardpaths OSX version uses Carbon though. You may want to use Cocoa API (which is newer), but it's Objective-C. DMD master now has some initial support for Objective-C. -- /Jacob Carlborg
Re: Template function that accept strings and array of strings
On 2015-07-16 18:49, badlink wrote: The method with the variadic function works, but I would have to use only one parameter because this doesn't work: fun(const(char[])[] a, const(char[])[] b ...) and is a bit ugly in my use case ... I don't think I really understand how you want to use/call the function. Could you give an example with all the different types you want to call the function? -- /Jacob Carlborg
Re: Working functionally with third party libraries
On Friday, 17 July 2015 at 09:07:29 UTC, Jarl André Hübenthal wrote: Or loop it. But its pretty nice to know that there is laziness in D, but when I query mongo I expect all docs to be retrieved, since there are no paging in the underlying queries? Thus, having a lazy functionality on top of non lazy db queries seem a bit off dont you think? From the client point of view db is sort of lazy: data is received from server as needed. Why would you want to put all data into an array before processing it? Why can't you process it from the range directly?
Re: Environment variable for application storage under OSX ?
On 2015-07-16 23:12, anonymous wrote:
I have the following code, working under Win and Linux:
---
import std.process: environment;
immutable string p;
static this() {
version(Win32) p = environment.get("APPDATA");
version(linux) p = "/home/" ~ environment.get("USER");
version(OSX) p = "?";
}
---
what would be the OSX equivalent (to get the path where the applications
data are commonmly stored)?
They are usually defined as constants in Objective-C. You can read more
about it here [1][2][3].
You can also use the CoreServices framework which has a C API [4]. But I
think it's deprecated and the preferred way is to use the Objective-C API's.
[1]
https://developer.apple.com/library/mac/documentation/FileManagement/Conceptual/FileSystemProgrammingGuide/AccessingFilesandDirectories/AccessingFilesandDirectories.html#//apple_ref/doc/uid/TP40010672-CH3-SW3
[2]
https://developer.apple.com/library/mac/documentation/FileManagement/Conceptual/FileSystemProgrammingGuide/AccessingFilesandDirectories/AccessingFilesandDirectories.html#//apple_ref/doc/uid/TP40010672-CH3-SW11
[3]
https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Miscellaneous/Foundation_Constants/index.html#//apple_ref/c/econst/NSApplicationSupportDirectory
[4]
http://stackoverflow.com/questions/5123361/finding-library-application-support-from-c
--
/Jacob Carlborg
Re: Environment variable for application storage under OSX ?
On 2015-07-17 09:33, Anonymous wrote: So for a software named 'SuperDownloader2015' it would be $HOME/Library/Application Support/SuperDownloader2015 right ? so it's not user-specific and it's writable for the current user ? sorry but it looks a bit strange, anyone can confirm ? Yes, that's correct. Some applications skip the "Application Support" directory and creates the "SuperDownloader2015" directory directly in $HOME/Library -- /Jacob Carlborg
Re: Working functionally with third party libraries
On Friday, 17 July 2015 at 11:47:30 UTC, sigod wrote: On Friday, 17 July 2015 at 09:07:29 UTC, Jarl André Hübenthal wrote: But its pretty nice to know that there is laziness in D, but when I query mongo I expect all docs to be retrieved, since there are no paging in the underlying queries? Thus, having a lazy functionality on top of non lazy db queries seem a bit off dont you think? Not true. There's paging in MongoDB. See [Cursors][0] and documentation for `find` method. Also, look at [`vibe.d`'s implementation][1]. [0]: http://docs.mongodb.org/manual/core/cursors/ [1]: https://github.com/rejectedsoftware/vibe.d/blob/master/source/vibe/db/mongo/cursor.d +1 good to know.
Re: Infinite range of nullable elements
On Friday, 17 July 2015 at 07:42:09 UTC, Roland Hadinger wrote:
Here's how I would implement the basic behaviour (could be
extended to also forward bidirectional and random access
functions):
---
auto cushion(R)(R r)
if (isInputRange!R)
{
static if (isInfinite!R) { return r; } else {
struct _Cushion(R)
{
R r;
alias E = ElementType!R;
alias NE = Nullable!E;
@property bool empty() { return false; }
@property NE front()
{
return !r.empty ? NE(r.front) : NE();
}
void popFront()
{
if (!r.empty) r.popFront();
}
}
return _Cushion!R(r);
}
}
---
I didn't find anything like this Phobos. Did I miss something?
The building blocks are there. You're `map`ping the original
range to `Nullable`, and then you're `chain`ing an infinite range
(`cycle`) of nulls behind.
import std.range: isInputRange;
auto cushion(R)(R r)
if (isInputRange!R)
{
import std.algorithm: map;
import std.range: chain, cycle, ElementType, only;
import std.typecons: Nullable;
alias E = ElementType!R;
alias NE = Nullable!E;
return chain(r.map!NE, NE().only.cycle);
}
Comparison of struct with Nullable member
Hello,
I came around a strange behavior and I'm not sure if it is a bug
or feature.
import std.typecons : Nullable;
struct Foo
{
string bar;
Nullable!int baz;
}
auto a = Foo("bb");
auto b = Foo("bb");
assert(a == b);
This ends up with: Called `get' on null Nullable!int
But if I change bar to be an int for example, than it passes ok.
I would expect this to pass ok.
Tested on dmd 2.067.1 win64
Re: Working functionally with third party libraries
On Friday, 17 July 2015 at 09:07:29 UTC, Jarl André Hübenthal wrote: But its pretty nice to know that there is laziness in D, but when I query mongo I expect all docs to be retrieved, since there are no paging in the underlying queries? Thus, having a lazy functionality on top of non lazy db queries seem a bit off dont you think? Not true. There's paging in MongoDB. See [Cursors][0] and documentation for `find` method. Also, look at [`vibe.d`'s implementation][1]. [0]: http://docs.mongodb.org/manual/core/cursors/ [1]: https://github.com/rejectedsoftware/vibe.d/blob/master/source/vibe/db/mongo/cursor.d
Re: Infinite range of nullable elements
On Friday, 17 July 2015 at 07:42:09 UTC, Roland Hadinger wrote: At this moment I'm tempted to implement a function taking a range of elements E and returning an infinite range of Nullable!E. [...] Wouldn't it still require the algorithms to check if an element isNull()? Calling get() on a null element will assert(). I'm wondering why it asserts instead of throwing.
Re: Working functionally with third party libraries
On Thursday, 16 July 2015 at 20:41:21 UTC, ZombineDev wrote:
On Thursday, 16 July 2015 at 20:17:54 UTC, Jarl André Hübenthal
wrote:
On Thursday, 16 July 2015 at 20:00:38 UTC, Ali Çehreli wrote:
On 07/16/2015 12:35 PM, "Jarl
=?UTF-8?B?QW5kcsOpIEjDvGJlbnRoYWwi?= "
wrote:
Hi
using mongo with vibe.d is easy. But I would like to skip
the foreach on
MongoCursor?
I mean, I want to use map!, filter! and reduce! on the
resulting docs.
Is there a fast way to convert MongoCursor to an array
without resolving
to ugly for loops with appender! ?
I've never used MongoCursor but judging from the fact that it
has empty, front, and popFront(), it is an InputRange:
http://vibed.org/api/vibe.db.mongo.cursor/MongoCursor
Have you tried using it with map and others? What errors do
you get?
Ali
Ah well I got another error now. Using the following code:
Resource[] getResource() {
auto coll = client.getCollection("app.resource");
return coll.find().map!(doc => deserialize!(BsonSerializer,
Resource)(doc));
}
I get this error:
src/app.d(51,21): Error: cannot implicitly convert expression
(map(coll.find())) of type MapResult!(__lambda1,
MongoCursor!(Bson, Bson, typeof(null))) to Resource[]
Most of the functions from std.algorithm and std.range return a
lazy range which you need to iterate over go get its elements.
To turn those ranges to an array you need add a .array at the
end (http://dlang.org/phobos/std_array#array). Here's a larger
example: http://d.readthedocs.org/en/latest/introduction.html.
Another option is to return the elements as a range (by making
return type of your function auto), instead of putting them
into a newly allocated array (with .array). This way may be a
bit more work (delaying the call to .array), but it can be
quite efficient because it removes the need to allocate memory.
Thanks. Its a lot more cleaner and syntactically readable having
.array at the end. But about laziness the same applies to clojure
and scala. In clojure you must force evaluate the list, in scala
you must to mostly the same as in D, put a toList or something at
the end. Or loop it. But its pretty nice to know that there is
laziness in D, but when I query mongo I expect all docs to be
retrieved, since there are no paging in the underlying queries?
Thus, having a lazy functionality on top of non lazy db queries
seem a bit off dont you think?
Getting Nth Row and Column from MatrixView, Scid library
Hi, I want to use Scid matrixes for implementing GMM algorithm. I will start by writing Naive Bayes with linear and quadratic decision boundaries . I reliaze Scid does not provides any functions for getting spesific row or coloumn. Matrixwview class only supplies opIndex function. Is there anything that I am missing or what is the best to get nth column or row with Scid library. Link to Scid lib: http://www.kyllingen.net/code/scid/doc/scid_matrix.html
Re: How to use core.thread.Thread
On Thursday, 16 July 2015 at 09:17:47 UTC, Daniel Kozák wrote:
class DerivedThread : Thread {
shared int count = 0;
}
I thought shared is only for whole of the object.
auto thr = new DerivedThread();
Here, "thr" is not shared but it's member thr.count is shared?
But if it's not shared, thr object referred by main thread and
"this" reference of DerivedThread.run() are different?
What happen if there are both shared and unshared member exists?
class DerivedThread : Thread {
shared int count = 0;
int foo = 0;
}
Umm. I can't imagine what's the memory layout of this object.
Re: Environment variable for application storage under OSX ?
On Friday, 17 July 2015 at 07:33:43 UTC, Anonymous wrote:
On Friday, 17 July 2015 at 07:14:24 UTC, FreeSlave wrote:
On Thursday, 16 July 2015 at 21:12:05 UTC, anonymous wrote:
I have the following code, working under Win and Linux:
---
import std.process: environment;
immutable string p;
static this() {
version(Win32) p = environment.get("APPDATA");
version(linux) p = "/home/" ~ environment.get("USER");
version(OSX) p = "?";
}
---
what would be the OSX equivalent (to get the path where the
applications data are commonmly stored)?
Hello. You may take a look at this library
https://github.com/MyLittleRobo/standardpaths
OSX version uses Carbon though. You may want to use Cocoa API
(which is newer), but it's Objective-C.
Also you may consider standard path for data storage without
using any api or spec. It's usually $HOME/Library/Application
Support/ on OSX.
So for a software named 'SuperDownloader2015' it would be
$HOME/Library/Application Support/SuperDownloader2015
right ?
so it's not user-specific and it's writable for the current
user ?
sorry but it looks a bit strange, anyone can confirm ?
It is user specific obviously since it's in user home.
Can you elaborate on what do you want exactly?
From Windows and Linux examples you provided I assumed you need
user-specific paths (APPDATA is defined per user on Windows).
System-wide application data path is different.
Infinite range of nullable elements
At this moment I'm tempted to implement a function taking a range
of elements E and returning an infinite range of Nullable!E.
With this function ("cushion" for a lack of better name) I could
do:
auto a = [0,1,2,3,4,5,6,7,8,9];
foreach (e ; a.cushion.take(20))
writeln(e); // exactly 20 elements
This would allow chaining together algorithms that need to look
ahead in a range.
Here's how I would implement the basic behaviour (could be
extended to also forward bidirectional and random access
functions):
---
auto cushion(R)(R r)
if (isInputRange!R)
{
static if (isInfinite!R) { return r; } else {
struct _Cushion(R)
{
R r;
alias E = ElementType!R;
alias NE = Nullable!E;
@property bool empty() { return false; }
@property NE front()
{
return !r.empty ? NE(r.front) : NE();
}
void popFront()
{
if (!r.empty) r.popFront();
}
}
return _Cushion!R(r);
}
}
---
I didn't find anything like this Phobos. Did I miss something? Is
this a bad idea for some reason?
Re: Environment variable for application storage under OSX ?
On Friday, 17 July 2015 at 07:14:24 UTC, FreeSlave wrote:
On Thursday, 16 July 2015 at 21:12:05 UTC, anonymous wrote:
I have the following code, working under Win and Linux:
---
import std.process: environment;
immutable string p;
static this() {
version(Win32) p = environment.get("APPDATA");
version(linux) p = "/home/" ~ environment.get("USER");
version(OSX) p = "?";
}
---
what would be the OSX equivalent (to get the path where the
applications data are commonmly stored)?
Hello. You may take a look at this library
https://github.com/MyLittleRobo/standardpaths
OSX version uses Carbon though. You may want to use Cocoa API
(which is newer), but it's Objective-C.
Also you may consider standard path for data storage without
using any api or spec. It's usually $HOME/Library/Application
Support/ on OSX.
So for a software named 'SuperDownloader2015' it would be
$HOME/Library/Application Support/SuperDownloader2015
right ?
so it's not user-specific and it's writable for the current user ?
sorry but it looks a bit strange, anyone can confirm ?
Re: Environment variable for application storage under OSX ?
On Thursday, 16 July 2015 at 21:12:05 UTC, anonymous wrote:
I have the following code, working under Win and Linux:
---
import std.process: environment;
immutable string p;
static this() {
version(Win32) p = environment.get("APPDATA");
version(linux) p = "/home/" ~ environment.get("USER");
version(OSX) p = "?";
}
---
what would be the OSX equivalent (to get the path where the
applications data are commonmly stored)?
Hello. You may take a look at this library
https://github.com/MyLittleRobo/standardpaths
OSX version uses Carbon though. You may want to use Cocoa API
(which is newer), but it's Objective-C.
Also you may consider standard path for data storage without
using any api or spec. It's usually $HOME/Library/Application
Support/ on OSX.
