• "Maxime Chevalier" <maximechevalierb gmail.com> Nov 20 2012
• Timon Gehr <timon.gehr gmx.ch> Nov 20 2012
• "bearophile" <bearophileHUGS lycos.com> Nov 20 2012
• Jacob Carlborg <doob me.com> Nov 20 2012

"Maxime Chevalier" <maximechevalierb gmail.com> writes:

I need to pass an array literal as a template parameter. The 
reference on this website seems to imply this is possible, but 
doesn't illustrate it. The obvious way doesn't seem to work:

mixin template MyTemplate(int[] arr) {}
Error: arithmetic/string type expected for value-parameter, not 
int[]

Is there no way to do this without using a mixin and CTFE? I 
don't think I can use tuple types because I need to initialize a 
struct member using the array literal parameter.

Timon Gehr <timon.gehr gmx.ch> writes:

On 11/21/2012 12:22 AM, Maxime Chevalier wrote:
 I need to pass an array literal as a template parameter. The reference
 on this website seems to imply this is possible, but doesn't illustrate
 it. The obvious way doesn't seem to work:

 mixin template MyTemplate(int[] arr) {}
 Error: arithmetic/string type expected for value-parameter, not int[]

 Is there no way to do this without using a mixin and CTFE? I don't think
 I can use tuple types because I need to initialize a struct member using
 the array literal parameter.


I guess it should work, and this is a compiler bug. You can work around 
the limitation by using a template alias parameter.

"bearophile" <bearophileHUGS lycos.com> writes:

Maxime Chevalier:

 I need to pass an array literal as a template parameter. The 
 reference on this website seems to imply this is possible, but 
 doesn't illustrate it. The obvious way doesn't seem to work:


It's a known compiler bug, already in Bugzilla.

In the meantime this is a workaround:

template Foo(Args...) if (Args.length == 1) {
     pragma(msg, Args[0]);
     enum Foo = Args;
}

void main() {
     enum double[] a = [10, 20, 30];
     auto x = Foo!a;
}


Bye,
bearophile

Jacob Carlborg <doob me.com> writes:

On 2012-11-21 00:22, Maxime Chevalier wrote:
 I need to pass an array literal as a template parameter. The reference
 on this website seems to imply this is possible, but doesn't illustrate
 it. The obvious way doesn't seem to work:

 mixin template MyTemplate(int[] arr) {}
 Error: arithmetic/string type expected for value-parameter, not int[]

 Is there no way to do this without using a mixin and CTFE? I don't think
 I can use tuple types because I need to initialize a struct member using
 the array literal parameter.


It seems an "alias" parameter is working:

mixin template MyTemplate(alias arr) {}

You might want to add some kind of template constraint on that.

-- 
/Jacob Carlborg