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Function template as template parameter
Dec 11, 2022
Andrey Zherikov
Dec 11, 2022
Salih Dincer
Dec 11, 2022
Ali Çehreli
Dec 11, 2022
Andrey Zherikov
December 11, 2022
Gravatar of Andrey ZherikovPosted by Andrey ZherikovReply
Andrey Zherikov
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I have this (very simplified) code:

void foo(alias callback)()
{
    callback!5;
}

static void print(int i)() { writeln(i); }
foo!print;

Is there a way to merge two last lines into one of a form like foo!(...something...)?

Note that callback parameter must be compile-time parameter as it represents a member of a type during introspection done by foo.

December 11, 2022
Gravatar of Salih DincerPosted by Salih Dincer
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Salih Dincer
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On Sunday, 11 December 2022 at 09:43:34 UTC, Andrey Zherikov wrote:

>

Note that callback parameter must be compile-time parameter as it represents a member of a type during introspection done by foo.

I can't quite understand the question, this already works:

void foo(alias callback)()
{
    import std.stdio : writefln;
    callback.writefln!"%s";
}

void main()
{
  auto i = [ 1, 2, 3 ];
  auto s = ["foo", "bar", "zoo"];

  foo!i;
  foo!s;

  foo!"hello, world!";

  enum a = 11, b = 22;
  foo!(a + b);
} /*
  [1, 2, 3]
  ["foo", "bar", "zoo"]
  hello, world!
  33
*/
December 11, 2022
Gravatar of Ali ÇehreliPosted by Ali Çehreli
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Ali Çehreli
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On 12/11/22 05:54, Salih Dincer wrote:
> On Sunday, 11 December 2022 at 09:43:34 UTC, Andrey Zherikov wrote:
>> Note that callback parameter must be compile-time parameter as it
>> represents a member of a type during introspection done by `foo`.
>
> I can't quite understand the question, this already works:

I think the OP is trying to create an anonymous template. I don't think it's possible.

The following works because the template has the name 'print':

// Named template:
static void print(int i)() {
    import std;
    writeln(i);
}

void main() {
    foo!print;
}

The following does not work when one attempts to use the template anonymously. Just trying to pass a template just like a lambda:

    foo!((int i)() {
            import std;
            writeln(i);
        });

Note how '(int i)()' is hoping to define a template.

Ali
December 11, 2022
Gravatar of Andrey ZherikovPosted by Andrey Zherikov
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Andrey Zherikov
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On Sunday, 11 December 2022 at 16:24:30 UTC, Ali Çehreli wrote:

>

On 12/11/22 05:54, Salih Dincer wrote:

>

On Sunday, 11 December 2022 at 09:43:34 UTC, Andrey Zherikov
wrote:

>

Note that callback parameter must be compile-time parameter
as it
represents a member of a type during introspection done by
foo.

I can't quite understand the question, this already works:

I think the OP is trying to create an anonymous template.

Yes

>

The following does not work when one attempts to use the template anonymously. Just trying to pass a template just like a lambda

Thanks for confirming this.