• Vino (11/11) Aug 27 2023 Hi All,
• Basile B. (16/27) Aug 28 2023 Problems is that "PATHEXT" is a runtime argument. If you really
• Basile B. (11/41) Aug 28 2023 To go further, the correct code for syntax you wanted to use is
• Vino (2/14) Aug 30 2023 Thank you

Vino <akashvino79 gmail.com> writes:

Hi All,

   The the below code is not working, hence requesting your help.

Code:
```
import std.stdio;
import std.process: environment;
void main () {
    int* ext(string) = &environment.get("PATHEXT");
    writeln(*ext);
}
```

Basile B. <b2.temp gmx.com> writes:

On Monday, 28 August 2023 at 06:38:50 UTC, Vino wrote:
 Hi All,

   The the below code is not working, hence requesting your help.

 Code:
 ```
 import std.stdio;
 import std.process: environment;
 void main () {
    int* ext(string) = &environment.get("PATHEXT");
    writeln(*ext);
 }
 ```

Problems is that "PATHEXT" is a runtime argument. If you really 
want to get a pointer to the function for that runtime argument 
you can use a lambda:

```d
import std.stdio;
import std.process: environment;
void main () {

     alias atGet = {return environment.get("PATHEXT");}; // really 
lazy

     writeln(atGet);         // pointer to the lambda
     writeln((*atGet)());    // call the lambda
}
```

There might be other ways, but less idiomatic (using a struct + 
opCall, a.k.a  a "functor")

Basile B. <b2.temp gmx.com> writes:

On Monday, 28 August 2023 at 10:20:14 UTC, Basile B. wrote:
 On Monday, 28 August 2023 at 06:38:50 UTC, Vino wrote:
 Hi All,

   The the below code is not working, hence requesting your 
 help.

 Code:
 ```
 import std.stdio;
 import std.process: environment;
 void main () {
    int* ext(string) = &environment.get("PATHEXT");
    writeln(*ext);
 }
 ```

 Problems is that "PATHEXT" is a runtime argument. If you really 
 want to get a pointer to the function for that runtime argument 
 you can use a lambda:

 ```d
 import std.stdio;
 import std.process: environment;
 void main () {

     alias atGet = {return environment.get("PATHEXT");}; // 
 really lazy

     writeln(atGet);         // pointer to the lambda
     writeln((*atGet)());    // call the lambda
 }
 ```

 There might be other ways, but less idiomatic (using a struct + 
 opCall, a.k.a  a "functor")

To go further, the correct code for syntax you wanted to use is 
actually

```d
alias Ext_T = string (const char[] a, string b); // define a 
function type
alias Ext_PT = Ext_T*; // define a function **pointer** type
Ext_PT ext = &environment.get;
```

But as you can see that does not allow to capture the argument. 
Also it only work as AliasDeclaration RHS.

Vino <akashvino79 gmail.com> writes:

On Monday, 28 August 2023 at 10:27:07 UTC, Basile B. wrote:
 On Monday, 28 August 2023 at 10:20:14 UTC, Basile B. wrote:
 [...]

 To go further, the correct code for syntax you wanted to use is 
 actually

 ```d
 alias Ext_T = string (const char[] a, string b); // define a 
 function type
 alias Ext_PT = Ext_T*; // define a function **pointer** type
 Ext_PT ext = &environment.get;
 ```

 But as you can see that does not allow to capture the argument. 
 Also it only work as AliasDeclaration RHS.

Thank you