• Tony (23/23) Nov 09 2017 Doing a port of some C code that has an #ifdef in the middle of
• Michael V. Franklin (33/56) Nov 09 2017 Here's my attempt. There's probably a more elegant way, but it's
• Tony (1/1) Nov 09 2017 Thanks Mike!

Tony <tonytdominguez aol.com> writes:

Doing a port of some C code that has an #ifdef in the middle of 
an initialization for an array of structs. I am getting a compile 
error trying to get equivalent behavior with "static if" or 
"version". Is there a way to achieve this other than making two 
separate array initialization sections?

struct a {
    int y;
    int z;
}

immutable string situation = "abc";

int main()
{
    a[] theArray = [
       { 10, 20 },
// version(abc)
static if (situation == "abc")
{
       { 30, 40 },
}
       { 50, 60 }
       ];
    return 0;
}

Michael V. Franklin <slavo5150 yahoo.com> writes:

On Friday, 10 November 2017 at 06:22:51 UTC, Tony wrote:
 Doing a port of some C code that has an #ifdef in the middle of 
 an initialization for an array of structs. I am getting a 
 compile error trying to get equivalent behavior with "static 
 if" or "version". Is there a way to achieve this other than 
 making two separate array initialization sections?

 struct a {
    int y;
    int z;
 }

 immutable string situation = "abc";

 int main()
 {
    a[] theArray = [
       { 10, 20 },
 // version(abc)
 static if (situation == "abc")
 {
       { 30, 40 },
 }
       { 50, 60 }
       ];
    return 0;
 }

Here's my attempt. There's probably a more elegant way, but it's 
the best I could do.

import std.stdio;

struct a {
     int y;
     int z;
}

enum situation = "abc";

int main()
{
     enum head = "a[] theArray = [ {10, 20},";
     static if (situation == "abc")
     {
         enum middle = "{ 30, 40},";	
     }
     else
     {
         enum middle = "";	
     }
     enum tail = "{ 50, 60 }];";
     mixin(head ~ middle ~ tail);
	
     writeln(head ~ middle ~ tail);
	
     return 0;
}

The use of enums for this is called manifest constants 
(https://dlang.org/spec/enum.html#manifest_constants).  It's more 
analogous to #define in C.

Mixins are documented here 
(https://dlang.org/spec/statement.html#mixin-statement)

Mike

Tony <tonytdominguez aol.com> writes:

Thanks Mike!