• Kevin Bailey (27/27) Jul 07 2021 I'm trying to use some fairly simple template argument deduction,
• =?UTF-8?Q?Ali_=c3=87ehreli?= (9/11) Jul 07 2021 There are other ways of achieving the same thing the simplest of which
• Paul Backus (2/11) Jul 07 2021 https://issues.dlang.org/show_bug.cgi?id=22111
• Tejas (24/51) Jul 07 2021 The following works:
• vit (16/43) Jul 07 2021 This work:

Kevin Bailey <keraba yahoo.com> writes:

I'm trying to use some fairly simple template argument deduction, 
but
maybe I'm not getting the syntax correct. C++ doesn't event blink 
at
something like this, but D is giving me:

temptest.d(18): Error: template temptest.func cannot deduce 
function from argument types !()(bar), candidates are:
temptest.d(10):        func(T)(foo!T.bar f)

I guess D can't crack open a type like that?

```
template foo(T)
{
class bar
{
         T t;
}

}

void func(T)(            // 10
         foo!(T).bar f)
{
}

int main()
{
         foo!int.bar fi;
         func(fi);        // 18
}
```

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

On 7/7/21 12:14 PM, Kevin Bailey wrote:

 fairly simple template argument deduction

It's not the simplest but it is still complicated. :)

 I guess D can't crack open a type like that?

There are other ways of achieving the same thing the simplest of which 
is probably the following:

void func(B)(B f) {
}

Apparently, there are additional constraints on B, which can be 
expressed in D with some flexibility, pragmatism, and optimism.

Ali

Paul Backus <snarwin gmail.com> writes:

On Wednesday, 7 July 2021 at 19:14:52 UTC, Kevin Bailey wrote:
 I'm trying to use some fairly simple template argument 
 deduction, but
 maybe I'm not getting the syntax correct. C++ doesn't event 
 blink at
 something like this, but D is giving me:

 temptest.d(18): Error: template temptest.func cannot deduce 
 function from argument types !()(bar), candidates are:
 temptest.d(10):        func(T)(foo!T.bar f)

 I guess D can't crack open a type like that?

https://issues.dlang.org/show_bug.cgi?id=22111

Tejas <notrealemail gmail.com> writes:

On Wednesday, 7 July 2021 at 19:14:52 UTC, Kevin Bailey wrote:
 I'm trying to use some fairly simple template argument 
 deduction, but
 maybe I'm not getting the syntax correct. C++ doesn't event 
 blink at
 something like this, but D is giving me:

 temptest.d(18): Error: template temptest.func cannot deduce 
 function from argument types !()(bar), candidates are:
 temptest.d(10):        func(T)(foo!T.bar f)

 I guess D can't crack open a type like that?

 ```
 template foo(T)
 {
 class bar
 {
         T t;
 }

 }

 void func(T)(            // 10
         foo!(T).bar f)
 {
 }

 int main()
 {
         foo!int.bar fi;
         func(fi);        // 18
 }
 ```



     The following works:
     ```d
     import std.stdio;
     template foo(T)
     {
     class bar
     {
             T t;
     }

}

     void func(T) (            // 10
             T f)               //  No need to repeat 
foo!(int).bar :)
     {
     }

     int main()
     {
             foo!(int).bar fi;//brackets added, now syntax is 
correct
             func(fi);        // 18. int couldn't get deduced here
         return 0;
     }
     ```

vit <vit vit.vit> writes:

On Wednesday, 7 July 2021 at 19:14:52 UTC, Kevin Bailey wrote:
 I'm trying to use some fairly simple template argument 
 deduction, but
 maybe I'm not getting the syntax correct. C++ doesn't event 
 blink at
 something like this, but D is giving me:

 temptest.d(18): Error: template temptest.func cannot deduce 
 function from argument types !()(bar), candidates are:
 temptest.d(10):        func(T)(foo!T.bar f)

 I guess D can't crack open a type like that?

 ```
 template foo(T)
 {
 class bar
 {
         T t;
 }

 }

 void func(T)(            // 10
         foo!(T).bar f)
 {
 }

 int main()
 {
         foo!int.bar fi;
         func(fi);        // 18
 }
 ```

This work:

```d
template foo(T){
         class bar{
     		T t;
         }
     }

void func(alias F : foo!T, T)(F.bar f){
}

void main(){
     	
     foo!int.bar fi;
     func(fi);

}

```