• JN (23/23) Feb 18 import std;
• monkyyy (9/32) Feb 18 what do you mean why, thats a enum use this:
• Julian Fondren (11/17) Feb 18 This isn't the
• Nick Treleaven (20/30) Feb 21 The mixin statement inserts the body of the template into main's

JN <666total wp.pl> writes:

     import std;

     void before()
     {
         writeln("Before");
     }

     void after()
     {
         writeln("After");
     }

     void add(int x, int y)
     {
         writeln(x + y);
     }

     template WrapCall(string call)
     {
         enum WrapCall = "before(); " ~ call ~ "; after();";
     }

     void main()
     {
         mixin WrapCall!"add(1, 2)";
     }

This doesn't work, if I change it to mixin(WrapCall!"add(1, 2")), 
it works, why?

monkyyy <crazymonkyyy gmail.com> writes:

On Wednesday, 18 February 2026 at 19:43:38 UTC, JN wrote:
     import std;

     void before()
     {
         writeln("Before");
     }

     void after()
     {
         writeln("After");
     }

     void add(int x, int y)
     {
         writeln(x + y);
     }

     template WrapCall(string call)
     {
         enum WrapCall = "before(); " ~ call ~ "; after();";
     }

     void main()
     {
         mixin WrapCall!"add(1, 2)";
     }

 This doesn't work, if I change it to mixin(WrapCall!"add(1, 
 2")), it works, why?

what do you mean why, thats a enum use this:

```d
void wrapcall(alias F,T...)(T args){
   before;
   F(args);
   after;
}
```

Julian Fondren <julian.fondren gmail.com> writes:

On Wednesday, 18 February 2026 at 19:43:38 UTC, JN wrote:
     void main()
     {
         mixin WrapCall!"add(1, 2)";
     }

 This doesn't work, if I change it to mixin(WrapCall!"add(1, 
 2")), it works, why?

This isn't the 
https://dlang.org/spec/statement.html#mixin-statement , and what 
your change does it make it that.

Contrast:

```d
void main() {
     mixin WrapCall!"add(1, 2)";
     mixin(WrapCall);
}
```

Nick Treleaven <nick geany.org> writes:

On Wednesday, 18 February 2026 at 19:43:38 UTC, JN wrote:
     template WrapCall(string call)
     {
         enum WrapCall = "before(); " ~ call ~ "; after();";
     }

     void main()
     {
         mixin WrapCall!"add(1, 2)";
     }

The mixin statement inserts the body of the template into main's 
scope, so this just declares a string enum:

```d
void main()
{
     enum WrapCall = "before(); " ~ "add(1, 2)" ~ "; after();";
}
```
Note that eponymous templates don't do anything special for mixin 
statements.

 This doesn't work, if I change it to mixin(WrapCall!"add(1, 
 2")), it works, why?

Because that string mixin takes an enum string template 
instantiation and parses it as if it were code inside main, so 
you get:

```d
void main()
{
     before(); add(1, 2); after();
}
```