gmlparser/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, either version 3 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  17  */
  18 module gmlparser.utils is aliced;
  19
  20
  21 // ////////////////////////////////////////////////////////////////////////// //
  22 // handy utility
  23 auto selector(RetType=void, T, A...) (T obj, scope A args) if (A.length > 0) {
  24   import std.traits : arity, isCallable, Parameters, ReturnType;
  25   foreach (immutable aidx, auto arg; args) {
  26     static assert(isCallable!(args[aidx]), "non-callable case #"~aidx.stringof);
  27     static if (arity!(args[aidx]) == 0) {
  28       static if (is(ReturnType!(args[aidx]) == void)) {
  29         arg();
  30         static if (!is(RetType == void)) return RetType.init; else return;
  31       } else {
  32         return cast(RetType)arg();
  33       }
  34     } else {
  35       static assert(arity!(args[aidx]) == 1, "invalid arity for case #"~aidx.stringof);
  36       static assert(is(Parameters!(A[aidx])[0] : T), "invalid delegate argument for case #"~aidx.stringof);
  37       // check for common error: `=> {}`
  38       static assert(!isCallable!(ReturnType!(A[aidx])), "you probably wrote '=>{}' in case #"~aidx.stringof);
  39       if (auto o = cast(Parameters!(A[aidx])[0])obj) {
  40         // i found her! ;-)
  41         static if (is(ReturnType!(args[aidx]) == void)) {
  42           arg(o);
  43           static if (!is(RetType == void)) return RetType.init; else return;
  44         } else {
  45           return cast(RetType)arg(o);
  46         }
  47       }
  48     }
  49   }
  50   static if (!is(RetType == void)) return RetType.init;
  51 }