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digitalmars.D.learn - compilers w/ different language features: version block

reply kdevel <kdevel vogtner.de> writes:
A code fragment using static foreach

https://forum.dlang.org/thread/jiefcxwqbjzqnmtazkwy forum.dlang.org#post-beruryblsptnunsowjph:40forum.dlang.org

does not compile with the current GDC (GCC 4.9.4 and 5.5.0). I 
tried to encapsulate this code into a version block but GDC still 
checks the syntax. Is there any more elegant way besides of using 
a mixin?:

    version (DigitalMars) {
       pragma (msg, "DMD");
       mixin (`
       enum typenames = ["float", "double", "real", "short", 
"int", "long"];
       static foreach (s; typenames) {
          pragma (msg, s);
          disp[s] = mixin ("&mymain!" ~ s);
       }
       `);
    }
Feb 24 2018
next sibling parent reply Seb <seb wilzba.ch> writes:
On Sunday, 25 February 2018 at 00:36:16 UTC, kdevel wrote:

 A code fragment using static foreach

 https://forum.dlang.org/thread/jiefcxwqbjzqnmtazkwy forum.dlang.org#post-beruryblsptnunsowjph:40forum.dlang.org

 does not compile with the current GDC (GCC 4.9.4 and 5.5.0). I 
 tried to encapsulate this code into a version block but GDC 
 still checks the syntax. Is there any more elegant way besides 
 of using a mixin?:

    version (DigitalMars) {
       pragma (msg, "DMD");
       mixin (`
       enum typenames = ["float", "double", "real", "short", 
 "int", "long"];
       static foreach (s; typenames) {
          pragma (msg, s);
          disp[s] = mixin ("&mymain!" ~ s);
       }
       `);
    }


Are you looking for something like this?

---
static if (__traits(compiles, () { static foreach (i; [0]){} }))
     version = supportsStaticForeach;

void main()
{
     version(supportsStaticForeach) {
        pragma(msg, "Yay, your compiler is new enough.");
     }
}
---


https://run.dlang.io/is/PZN5Nv


 Is there any more elegant way besides of using a mixin?:


Don't support GDC (or only GDC-master)?
Feb 24 2018
parent reply Seb <seb wilzba.ch> writes:
On Sunday, 25 February 2018 at 00:42:20 UTC, Seb wrote:

 On Sunday, 25 February 2018 at 00:36:16 UTC, kdevel wrote:

    [...]


 Are you looking for something like this?

 ---
 static if (__traits(compiles, () { static foreach (i; [0]){} }))
     version = supportsStaticForeach;

 void main()
 {
     version(supportsStaticForeach) {
        pragma(msg, "Yay, your compiler is new enough.");
     }
 }
 ---


 https://run.dlang.io/is/PZN5Nv


 [...]


 Don't support GDC (or only GDC-master)?


Ah sorry I replied too fast. Yeah `mixin` is the only way to 
workaround this if you really, really have to support GDC.
Feb 24 2018
parent Seb <seb wilzba.ch> writes:
On Sunday, 25 February 2018 at 01:19:02 UTC, Seb wrote:

 On Sunday, 25 February 2018 at 00:42:20 UTC, Seb wrote:

 On Sunday, 25 February 2018 at 00:36:16 UTC, kdevel wrote:

    [...]


 Are you looking for something like this?

 ---
 static if (__traits(compiles, () { static foreach (i; [0]){} 
 }))
     version = supportsStaticForeach;

 void main()
 {
     version(supportsStaticForeach) {
        pragma(msg, "Yay, your compiler is new enough.");
     }
 }
 ---


 https://run.dlang.io/is/PZN5Nv


 [...]


 Don't support GDC (or only GDC-master)?


 Ah sorry I replied too fast. Yeah `mixin` is the only way to 
 workaround this if you really, really have to support GDC.


BTW there's one trick that might work on your setup - conditional 
imports:

---
static if (__traits(compiles, () { static foreach (i; [0]){} }))
     version = supportsStaticForeach;

void main()
{
     version(supportsStaticForeach) {
        import compat.staticforeach;
     } else {
        import compat.no_staticforeach;
     }
}
---

With rdmd this should work out of the box - with DUB you would 
need to tweak the source paths. DUB allows all options to be 
compiler-specific, so e.g. something like this for a dub.sdl 
could work:

---
sourcePaths-dmd "compat/staticforeach"
sourcePaths-ldc "compat/staticforeach"
sourcePaths-gdc "compat/no_staticforeach"
---
Feb 24 2018
prev sibling parent Jonathan M Davis <newsgroup.d jmdavisprog.com> writes:
On Sunday, February 25, 2018 00:36:16 kdevel via Digitalmars-d-learn wrote:

 A code fragment using static foreach

 https://forum.dlang.org/thread/jiefcxwqbjzqnmtazkwy forum.dlang.org#post-b
 eruryblsptnunsowjph:40forum.dlang.org

 does not compile with the current GDC (GCC 4.9.4 and 5.5.0). I
 tried to encapsulate this code into a version block but GDC still
 checks the syntax. Is there any more elegant way besides of using
 a mixin?:

     version (DigitalMars) {
        pragma (msg, "DMD");
        mixin (`
        enum typenames = ["float", "double", "real", "short",
 "int", "long"];
        static foreach (s; typenames) {
           pragma (msg, s);
           disp[s] = mixin ("&mymain!" ~ s);
        }
        `);
     }


For static foreach? No. As I undarstand it, because of how the grammar works
with static foreach, there is no way to have it in the code (other than a
string mixin) unless the compiler supports it.

If you want to use newer features, I would suggest avoiding gdc until they
finish playing catch-up. They have yet to do an official release that's more
up-to-date than 2.068.2 of the front-end. When the frontend switched from
C++ to D, the gdc folks did a lot of rewriting to update their stuff, and
it's taken them a while to finish. What they have on github should be more
up-to-date, but I don't know what state it's in, and they have yet to do a
release with all of those updates. At some point, the gdc guys will catch
up, but for now, it's probably better to avoid it - especially if you want
to use newer features like static foreach.

So, I would suggest that you either use dmd or ldc. ldc has actually managed
to stay fairly up-to-date and is usually at most a release or so behind dmd.

But if you really want code to work with both gdc and and newer compilers,
then as far as static foreach goes, you'll have to do stuff like use string
mixins or different files for different compilers. Unfortunately, you can't
just use different version blocks.

- Jonathan M Davis
Feb 24 2018