d - Compile-time foreach outside function body -

is there way have foreach outside function body ex. generating code.

my scenario have associative array @ compile-time need use generate specific fields. unfortunately can't use foreach outside of function body generate members.

right using work-around have few mixins give 1 aa first mixin , mixin converts aa array , passes second mixin, second mixin recursive ng until there no more member, while calling first member in array, calls third mixin can use generate code.

it's not smooth , dynamic want , wondering if has better solution.

here solution

// first mixin takes associative array , string mixin handle items mixin template staticforeachaa(tkey,tvalue, tkey[tvalue] enumerator, string itemmixin) {         enum array = arrayaa!(tkey,tvalue)(enumerator); // converts aa array of key-value pair structs     alias arraytype = keyvaluepair!(tkey,tvalue);      mixin staticforeacharray!(arraytype, array, itemmixin); // calls second mixin array }  // second mixin "fake loops" array mixin template staticforeacharray(t, t[] array, string itemmixin) {     static if (array.length) {         import std.string : format;          mixin(format("mixin %s!(t, array[0]);", itemmixin)); // mixins itemmixin handle current item         mixin staticforeacharray!(t, array[1 .. $], itemmixin); // slices array remove item handled     } }  // third mixin can used whatever has done item mixin template staticforeachitem(t, t item) {     import std.conv : to;     pragma(msg, to!string(item)); } 

and "fake foreach" associative

enum aa = [0 : 1, 1 : 2, 2 : 3];  mixin staticforeachaa!(int, int, aa, "staticforeachitem"); 

this print key-value pairs aa @ compile-time.

leveraging power of compile-time functione excution (ctfe) make helper function generates code using data associative array (aa) provide.

import std.string : format;  string generatecodeforeachaa(tkey, tvalue)(tvalue[tkey] data, string foreachbody) {   string result;   foreach(k, v ; data)   {     result ~= format(foreachbody, k, v);   }    return result; } 

this function turns given aa data string formatting given foreachbody each aa element. returned string can mixin'ed:

enum data = [ 0 : 1, 1 : 2, 2 : 3 ];  enum code = generatecodeforeachaa(data, q{ pragma(msg, "%1$s => %2$s"); });  pragma(msg, "code: " ~ code);  mixin(code); 

output:

code:  pragma(msg, "0 => 1");  pragma(msg, "1 => 2");  pragma(msg, "2 => 3"); 0 => 1 1 => 2 2 => 3 

using generate members within struct:

struct foo {   enum members = [ "foo": 123, "bar": 42 ];   mixin(generatecodeforeachaa(members, q{ typeof(%2$s) %1$s = %2$s; })); }  void main() {   import std.stdio : writeln;    foo f;   writeln("foo: ", f.foo);   writeln("bar: ", f.bar); } 

output:

foo: 123 bar: 42