Capture parameter identifier name in a template?

[Rémy Mouëza via Digitalmars-d-learn]

I have just checked it and yes, it works with a constant that is not an 
enum: `const int FOO` defined in the module namespace or `static int 
BAR` defined in the dummy Vm class.

On 08/14/2014 02:08 PM, Maxime Chevalier-Boisvert wrote:
 > Thanks. Does it also work with a constant that's not an enum, e.g.: 
const int FOO?
 >
 > On 08/14/2014 01:23 PM, Rémy Mouëza wrote:
 >> Using __traits (identifier, ...) and a template alias seems to work 
for me:
 >>
 >> import std.stdio;
 >>
 >> /// Two kinds of enums:
 >>
 >> /// A named enum.
 >> enum VmParams {
 >>      OBJ_MIN_CAP,
 >>      PROTO_SLOT_IDX,
 >>      FPTR_SLOT_IDX,
 >> }
 >>
 >> /// An anonymous one.
 >> enum {
 >>      ATTR_CONFIGURABLE = 3,
 >>      ATTR_WRITABLE,
 >>      ATTR_ENUMERABLE,
 >>      ATTR_DELETED,
 >>      ATTR_GETSET,
 >>      ATTR_DEFAULT
 >> }
 >>
 >> /// A dummy Vm class for example purpose.
 >> class Vm {
 >>      /// Stores values.
 >>      int [string] table;
 >>
 >>      /// The "classic" runtime const API.
 >>      void defRTConst (string id, int val) {
 >>          table [id] = val;
 >>      }
 >>
 >>      /// Using an alias with the identifier trait.
 >>      void rtConst (alias p) () {
 >>          table [__traits (identifier, p)] = p;
 >>      }
 >>
 >>      /// Initializes our .table member.
 >>      this () {
 >>          /// Using the allMembers traits we can process all the members
 >> of a
 >>          /// named enum.
 >>          foreach (member; __traits (allMembers, VmParams)) {
 >>              int value = mixin ("VmParams." ~ member);
 >>              this.defRTConst (member, value);
 >>          }
 >>
 >>          /// Without duplicating the name and its value.
 >>          rtConst!ATTR_CONFIGURABLE;
 >>          rtConst!ATTR_WRITABLE;
 >>          rtConst!ATTR_ENUMERABLE;
 >>          rtConst!ATTR_DELETED;
 >>          rtConst!ATTR_GETSET;
 >>          rtConst!ATTR_DEFAULT;
 >>
 >>          /* rtConst won't work with local variables:
 >>          //  auto foo = ATTR_DEFAULT;
 >>          //  rtConst!foo;
 >>          The code above raises a compiler error:
 >>              Error: template instance rtConst!(foo) cannot use local
 >> 'foo' as parameter to non-global template rtConst(alias p)()
 >>          */
 >>      }
 >> }
 >>
 >> void main ()  {
 >>      Vm vm = new Vm;
 >>      vm.table.writeln;
 >>
 >>      /// output:
 >>      /// ["OBJ_MIN_CAP":0, "ATTR_WRITABLE":4, "ATTR_ENUMERABLE":5,
 >> "ATTR_GETSET":7, "PROTO_SLOT_IDX":1, "FPTR_SLOT_IDX":2,
 >> "ATTR_CONFIGURABLE":3, "ATTR_DELETED":6, "ATTR_DEFAULT":8]
 >> }
 >>
 >>
 >> On 08/12/2014 07:36 PM, Maxime Chevalier-Boisvert wrote:
 >>> In my JavaScript VM, I have a function whose purpose is to expose 
D/host
 >>> constants to the JavaScript runtime code running inside the VM. This
 >>> makes for somewhat redundant code, as follows:
 >>>
 >>> vm.defRTConst("OBJ_MIN_CAP"w, OBJ_MIN_CAP);
 >>> vm.defRTConst("PROTO_SLOT_IDX"w, PROTO_SLOT_IDX);
 >>> vm.defRTConst("FPTR_SLOT_IDX"w, FPTR_SLOT_IDX);
 >>> vm.defRTConst("ATTR_CONFIGURABLE"w  , ATTR_CONFIGURABLE);
 >>> vm.defRTConst("ATTR_WRITABLE"w      , ATTR_WRITABLE);
 >>> vm.defRTConst("ATTR_ENUMERABLE"w    , ATTR_ENUMERABLE);
 >>> vm.defRTConst("ATTR_DELETED"w       , ATTR_DELETED);
 >>> vm.defRTConst("ATTR_GETSET"w        , ATTR_GETSET);
 >>> vm.defRTConst("ATTR_DEFAULT"w       , ATTR_DEFAULT);
 >>>
 >>> I'm just wondering if there's a way to template defRTConst so that the
 >>> name of an identifier I'm passing (e.g.: ATTR_DEFAULT) can be captured
 >>> by the template, making it so that I don't also need to pass the 
name as
 >>> a string. I expect the answer to be no, but maybe someone with more
 >>> knowledge of D template magic knows better.
 >>