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digitalmars.D.learn - Equivalent of C++ #__VA_ARGS__

reply Ronoroa <aravind.nujella gmail.com> writes:
How do I achieve equivalent semantics of following C++ code?

```
#define
<< print_func(__VA_ARGS__) << std::endl;
```
Aug 02 2020
parent reply Adam D. Ruppe <destructionator gmail.com> writes:
On Sunday, 2 August 2020 at 15:30:27 UTC, Ronoroa wrote:

 How do I achieve equivalent semantics of following C++ code?

 ```
 #define
 << print_func(__VA_ARGS__) << std::endl;
 ```


You probably just want


void dbg(Args...)(Args args, size_t line = __LINE__) {
      writeln(line, args, " = ", print_func(args));
}
Aug 02 2020
parent reply Ronoroa <aravind.nujella gmail.com> writes:
On Sunday, 2 August 2020 at 15:48:34 UTC, Adam D. Ruppe wrote:

 On Sunday, 2 August 2020 at 15:30:27 UTC, Ronoroa wrote:
 void dbg(Args...)(Args args, size_t line = __LINE__) {
      writeln(line, args, " = ", print_func(args));
 }




I've tried

void dbg(Args...)(Args args, size_t line = __LINE__) {

     // print_func is simply writeln
     writeln(args);
}

void main() {
     int a = 10, b = 4;


     //                            ^^^^ this
     dbg(a, b);
}
Aug 02 2020
parent reply Adam D. Ruppe <destructionator gmail.com> writes:
On Sunday, 2 August 2020 at 16:05:07 UTC, Ronoroa wrote:

 That doesn't seem to stringize the args part like in 



oh yeah i missed that part.

D basically can't do that exactly, but if you pass the args as 
template things directly you can do this:

---
void main(string[] args) {
         int a;
         int b = 34;
         dbg!(a, b); // notice the !
}

void dbg(Args...)(size_t line = __LINE__) {
         import std.stdio;


         foreach(idx, alias arg; Args) {
                 if(idx) write(", ");
                 write(arg.stringof, " = ", arg);
         }
         writeln();
}
---




Or reformat the output however you want.
Aug 02 2020
parent Ronoroa <aravind.nujella gmail.com> writes:
On Sunday, 2 August 2020 at 16:31:50 UTC, Adam D. Ruppe wrote:

 On Sunday, 2 August 2020 at 16:05:07 UTC, Ronoroa wrote:

 That doesn't seem to stringize the args part like in 



 oh yeah i missed that part.

 D basically can't do that exactly, but if you pass the args as 
 template things directly you can do this:

 ---
 void main(string[] args) {
         int a;
         int b = 34;
         dbg!(a, b); // notice the !
 }

 void dbg(Args...)(size_t line = __LINE__) {
         import std.stdio;


         foreach(idx, alias arg; Args) {
                 if(idx) write(", ");
                 write(arg.stringof, " = ", arg);
         }
         writeln();
 }
 ---



 
 Or reformat the output however you want.


That's so much nicer than the C++ macro. Thanks a lot!
Aug 02 2020