• Gorge Jingale (3/3) Jul 24 2016 Is there a static ternary if?
• =?UTF-8?Q?Ali_=c3=87ehreli?= (10/13) Jul 24 2016 The way to force an expression at compile time is to use it for
• lqjglkqjsg (21/36) Jul 25 2016 It also works for "real" enumerated types.
• Cauterite (11/14) Jul 25 2016 You can pretty easily make your own;
• Gorge Jingale (4/20) Jul 25 2016 Cool, that would work. I don't think the lazy evaluation is a
• Michael Coulombe (3/26) Jul 25 2016 If that's ok, then try out std.traits.Select or std.traits.select:
• Cauterite (3/6) Jul 26 2016 Damn, I looked real hard for that template, I knew it existed. I

Gorge Jingale <Frifj mail.com> writes:

Is there a static ternary if?

(A == B) ? C : D;

for compile type that works like static if.

=?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:

On 07/24/2016 07:15 PM, Gorge Jingale wrote:
 Is there a static ternary if?

 (A == B) ? C : D;

 for compile type that works like static if.

The way to force an expression at compile time is to use it for 
something that's needed at compile time. For example, you can initialize 
a manifest constant (enum) with that expression:

void main() {
     enum i = (__MODULE__.length % 2) ? 42 : 43;
     pragma(msg, i);
}

Instead of enum, you can use 'static const' as well.

Ali

lqjglkqjsg <lqjglkqghjghjjsg lkdsf.od> writes:

On Monday, 25 July 2016 at 05:00:23 UTC, Ali Çehreli wrote:
 On 07/24/2016 07:15 PM, Gorge Jingale wrote:
 Is there a static ternary if?

 (A == B) ? C : D;

 for compile type that works like static if.

 The way to force an expression at compile time is to use it for 
 something that's needed at compile time. For example, you can 
 initialize a manifest constant (enum) with that expression:

 void main() {
     enum i = (__MODULE__.length % 2) ? 42 : 43;
     pragma(msg, i);
 }

 Instead of enum, you can use 'static const' as well.

 Ali

It also works for "real" enumerated types.

********************************
enum ver = 0; // version(Windows) ... else ....

enum VersionRelative1
{
     A = ver ? 1 : 2,
     B = ver ? 3 : 4,
}

enum VersionRelative2
{
     A = !ver ? 1 : 2,
     B = !ver ? 3 : 4,
}

unittest
{
     static assert(VersionRelative1.A == 2);
     static assert(VersionRelative2.A == 1);
}
********************************

which is quite cool and not widely known.

Cauterite <cauterite gmail.com> writes:

On Monday, 25 July 2016 at 02:15:12 UTC, Gorge Jingale wrote:
 Is there a static ternary if?

 (A == B) ? C : D;

 for compile type that works like static if.

You can pretty easily make your own;

   template staticIf(bool cond, alias a, alias b) {
     static if (cond) {
       alias staticIf = a;
     } else {
       alias staticIf = b;
     };
   };

The drawback is that there's no 'short-circuiting'; a and b are 
both evaluated.

Gorge Jingale <Frifj mail.com> writes:

On Monday, 25 July 2016 at 22:27:11 UTC, Cauterite wrote:
 On Monday, 25 July 2016 at 02:15:12 UTC, Gorge Jingale wrote:
 Is there a static ternary if?

 (A == B) ? C : D;

 for compile type that works like static if.

 You can pretty easily make your own;

   template staticIf(bool cond, alias a, alias b) {
     static if (cond) {
       alias staticIf = a;
     } else {
       alias staticIf = b;
     };
   };

 The drawback is that there's no 'short-circuiting'; a and b are 
 both evaluated.

Cool, that would work. I don't think the lazy evaluation is a 
problem at compile time? Just makes for longer times, but should 
be pretty minuscule.

Michael Coulombe <kirsybuu gmail.com> writes:

On Monday, 25 July 2016 at 22:57:05 UTC, Gorge Jingale wrote:
 On Monday, 25 July 2016 at 22:27:11 UTC, Cauterite wrote:
 On Monday, 25 July 2016 at 02:15:12 UTC, Gorge Jingale wrote:
 Is there a static ternary if?

 (A == B) ? C : D;

 for compile type that works like static if.

 You can pretty easily make your own;

   template staticIf(bool cond, alias a, alias b) {
     static if (cond) {
       alias staticIf = a;
     } else {
       alias staticIf = b;
     };
   };

 The drawback is that there's no 'short-circuiting'; a and b 
 are both evaluated.

 Cool, that would work. I don't think the lazy evaluation is a 
 problem at compile time? Just makes for longer times, but 
 should be pretty minuscule.

If that's ok, then try out std.traits.Select or std.traits.select:
https://dlang.org/phobos/std_traits.html#Select

Cauterite <cauterite gmail.com> writes:

On Tuesday, 26 July 2016 at 00:54:59 UTC, Michael Coulombe wrote:
 If that's ok, then try out std.traits.Select or 
 std.traits.select:
 https://dlang.org/phobos/std_traits.html#Select

Damn, I looked real hard for that template, I knew it existed. I 
expected it to be in std.meta though.