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digitalmars.D - Idioms you use

reply Freddy <Hexagonalstar64 gmail.com> writes:
Are any D idioms you use that you like to share?
Heres one of mine
---
enum ctfe =
{
     return 0xdead & 0xbad;
}();
---
Sep 28 2015
next sibling parent lobo <swamplobo gmail.com> writes:
On Monday, 28 September 2015 at 21:40:45 UTC, Freddy wrote:

 Are any D idioms you use that you like to share?
 Heres one of mine
 ---
 enum ctfe =
 {
     return 0xdead & 0xbad;
 }();
 ---


What does this do and where would it be useful in my code?

For D idioms I usually go here...you may want to submit a PR:

http://p0nce.github.io/d-idioms/

Phobos is another good source of how to do X in D.

bye,
lobo
Sep 28 2015
prev sibling next sibling parent Cauterite <cauterite gmail.com> writes:
On Monday, 28 September 2015 at 21:40:45 UTC, Freddy wrote:

 Are any D idioms you use that you like to share?


I'm not sure if these fit under the definition of 'idiom', but 
they sort of are… I think.
http://dpaste.dzfl.pl/f66a76a7411f

You could even extend the concept with opDispatch to achieve 
syntax like this:
pinvoke.psapi.GetProcessImageFileNameW!uint(...);

I've used a similar technique (+ caching) to lazily load OpenGL 
extensions. It worked really well.
Sep 29 2015
prev sibling next sibling parent reply anonymous <anonymous example.com> writes:
On Monday 28 September 2015 23:40, Freddy wrote:


 Are any D idioms you use that you like to share?
 Heres one of mine
 ---
 enum ctfe =
 {
      return 0xdead & 0xbad;
 }();
 ---


Why not just `enum ctfe = 0xdead & 0xbad;`?

Are there cases where `enum foo = {return bar;}();` works but `enum foo = 
bar;` doesn't? And if there are, aren't they compiler bugs?
Sep 29 2015
next sibling parent reply Cauterite <cauterite gmail.com> writes:
On Tuesday, 29 September 2015 at 12:52:36 UTC, anonymous wrote:

 Why not just `enum ctfe = 0xdead & 0xbad;`?

 Are there cases where `enum foo = {return bar;}();` works but 
 `enum foo = bar;` doesn't? And if there are, aren't they 
 compiler bugs?


I'm pretty sure he's talking about the general use of an 
anonymous function invocation assigned to an enum to force some 
statements to be executed at compile time. His example was not 
very illustrative though.
Sep 29 2015
parent anonymous <anonymous example.com> writes:
On Tuesday 29 September 2015 15:06, Cauterite wrote:


 some statements


Buf of course! I totally didn't think of multiple statements. Thanks.
Sep 29 2015
prev sibling parent Adam D. Ruppe <destructionator gmail.com> writes:
On Tuesday, 29 September 2015 at 12:52:36 UTC, anonymous wrote:

 Are there cases where `enum foo = {return bar;}();` works but 
 `enum foo = bar;` doesn't? And if there are, aren't they 
 compiler bugs?


If it is more complex than just one statement, putting it in a 
function lets you execute multiple lines (including loops and 
stuff) at once.
Sep 29 2015
prev sibling parent reply Marco Leise <Marco.Leise gmx.de> writes:
Am Mon, 28 Sep 2015 21:40:43 +0000
schrieb Freddy <Hexagonalstar64 gmail.com>:


 Are any D idioms you use that you like to share?
 Heres one of mine
 ---
 enum ctfe =
 {
      return 0xdead & 0xbad;
 }();
 ---


Yep, using that often, although I try to get my head around
using functional style one-line expressions where possible to
avoid the boilerplate.

static immutable ctfe = {
    bool[256] result;
    foreach (i; 0 .. 256)
        result = isDigit(i);
    return result;
}();

==>

static immutable bool[256] ctfe = iota(256).map!isDigit.array;

==>

static ctfe = ctfeArr!( iota(256).map!isDigit );

enum ctfeArr(alias r)()
{
	// r.length doesn't work as static array size
	enum length = r.length;
	// immutable doesn't work on this (cannot modify const)
	ElementType!(typeof(r))[length] result = r.array;
	// Cross fingers here ...
	return cast(immutable) result;
}

-- 
Marco
Oct 03 2015
parent reply Artur Skawina via Digitalmars-d <digitalmars-d puremagic.com> writes:
On 10/03/15 15:53, Marco Leise via Digitalmars-d wrote:

 Am Mon, 28 Sep 2015 21:40:43 +0000
 schrieb Freddy <Hexagonalstar64 gmail.com>:
 

 Are any D idioms you use that you like to share?
 Heres one of mine
 ---
 enum ctfe =
 {
      return 0xdead & 0xbad;
 }();
 ---


 
 Yep, using that often, although I try to get my head around
 using functional style one-line expressions where possible to
 avoid the boilerplate.
 
 static immutable ctfe = {
     bool[256] result;
     foreach (i; 0 .. 256)
         result = isDigit(i);
     return result;
 }();
 
 ==>
 
 static immutable bool[256] ctfe = iota(256).map!isDigit.array;
 
 ==>
 
 static ctfe = ctfeArr!( iota(256).map!isDigit );
 
 enum ctfeArr(alias r)()
 {
 	// r.length doesn't work as static array size
 	enum length = r.length;
 	// immutable doesn't work on this (cannot modify const)
 	ElementType!(typeof(r))[length] result = r.array;
 	// Cross fingers here ...
 	return cast(immutable) result;
 }


==>

   static ctfe = ctfeArr!( iota(256).map!isDigit() );

   immutable typeof(R.front)[R.array().length] ctfeArr(alias R) = R.array();


[`array` is only required because of compiler issues, yes.]

artur
Oct 03 2015
parent reply Marco Leise <Marco.Leise gmx.de> writes:
Am Sun, 04 Oct 2015 00:08:39 +0200
schrieb Artur Skawina via Digitalmars-d
<digitalmars-d puremagic.com>:


    static ctfe = ctfeArr!( iota(256).map!isDigit() );
 
    immutable typeof(R.front)[R.array().length] ctfeArr(alias R) = R.array();


I like that. Also that 1) In D everything is possible. And 2)
If not, there is a workaround, goto 1).

-- 
Marco
Oct 05 2015
parent Artur Skawina via Digitalmars-d <digitalmars-d puremagic.com> writes:
On 10/05/15 17:53, Marco Leise via Digitalmars-d wrote:

 Am Sun, 04 Oct 2015 00:08:39 +0200
 schrieb Artur Skawina via Digitalmars-d
 <digitalmars-d puremagic.com>:
 

    static ctfe = ctfeArr!( iota(256).map!isDigit() );

    immutable typeof(R.front)[R.array().length] ctfeArr(alias R) = R.array();


 
 I like that. Also that 1) In D everything is possible. And 2)
 If not, there is a workaround, goto 1).


Note that I just wanted to show that the ctfeArr /function/ was not
necessary, and I didn't want that `ctfe` declaration to be affected;
real code would look more like:

   enum typeof(R.front)[R.array().length] ctfeArr(alias R) = R.array();
   immutable ctfe = ctfeArr!( iota(256).map!isDigit() );

artur
Oct 05 2015