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digitalmars.D.learn - Function template as template parameter

reply Andrey Zherikov <andrey.zherikov gmail.com> writes:
I have this (very simplified) code:
```d
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`.
Dec 11 2022
parent reply Salih Dincer <salihdb hotmail.com> writes:
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:

```d
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
*/
```
Dec 11 2022
parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
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
Dec 11 2022
parent Andrey Zherikov <andrey.zherikov gmail.com> writes:
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.
Dec 11 2022