gaem/parser/utils.d

   1 /* GML parser
   2  * coded by Ketmar // Invisible Vector <ketmar@ketmar.no-ip.org>
   3  * Understanding is not required. Only obedience.
   4  *
   5  * This program is free software: you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation, version 3 of the License ONLY.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  16  */
  17 module gaem.parser.utils is aliced;
  18
  19
  20 // ////////////////////////////////////////////////////////////////////////// //
  21 // handy utility
  22 auto selector(RetType=void, T, A...) (T obj, scope A args) if (A.length > 0) {
  23   import std.traits : arity, isCallable, Parameters, ReturnType;
  24   foreach (immutable aidx, auto arg; args) {
  25     static assert(isCallable!(args[aidx]), "non-callable case #"~aidx.stringof);
  26     static if (arity!(args[aidx]) == 0) {
  27       static if (is(ReturnType!(args[aidx]) == void)) {
  28         arg();
  29         static if (!is(RetType == void)) return RetType.init; else return;
  30       } else {
  31         return cast(RetType)arg();
  32       }
  33     } else {
  34       static assert(arity!(args[aidx]) == 1, "invalid arity for case #"~aidx.stringof);
  35       static assert(is(Parameters!(A[aidx])[0] : T), "invalid delegate argument for case #"~aidx.stringof);
  36       // check for common error: `=> {}`
  37       static assert(!isCallable!(ReturnType!(A[aidx])), "you probably wrote '=>{}' in case #"~aidx.stringof);
  38       if (auto o = cast(Parameters!(A[aidx])[0])obj) {
  39         // i found her! ;-)
  40         static if (is(ReturnType!(args[aidx]) == void)) {
  41           arg(o);
  42           static if (!is(RetType == void)) return RetType.init; else return;
  43         } else {
  44           return cast(RetType)arg(o);
  45         }
  46       }
  47     }
  48   }
  49   static if (!is(RetType == void)) return RetType.init;
  50 }