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1   ////////////////////////////////////////////////////////////////////////////////
2   // MillScript: an Open Spice interpreter and batch website creation tool
3   // Copyright (C) 2001-2004 Open World Ltd
4   // Copyright (C) 2005 Kevin Rogers
5   //
6   // This file is part of MillScript.
7   //
8   // MillScript is free software; you can redistribute it and/or modify it under
9   // the terms of the GNU General Public License as published by the Free
10  // Software Foundation; either version 2 of the License, or (at your option)
11  // any later version.
12  //
13  // MillScript is distributed in the hope that it will be useful, but WITHOUT
14  // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
15  // FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
16  // more details.
17  //
18  // You should have received a copy of the GNU General Public License along with
19  // MillScript; if not, write to the Free Software Foundation, Inc., 59 Temple
20  // Place, Suite 330, Boston, MA  02111-1307  USA
21  ////////////////////////////////////////////////////////////////////////////////
22  package org.millscript.millscript.functions;
23  
24  import org.millscript.millscript.vm.Machine;
25  import org.millscript.millscript.vm.Package;
26  
27  /**
28   * This class the common functionality required for a two argument function
29   * which returns a single result. This class allows simple binary functions to
30   * be implemented very easily.
31   */
32  public abstract class BinaryFunction extends Function {
33  
34      /**
35       * @see Function#Function()
36       */
37      public BinaryFunction() {
38          super();
39      }
40  
41      /**
42       * @see Function#Function(Package)
43       */
44      public BinaryFunction( final Package p ) {
45          super( p );
46      }
47  
48      /**
49       * @see org.millscript.millscript.functions.Function#apply(org.millscript.millscript.vm.Machine, int)
50       */
51      @Override
52      public void apply( final Machine mc, final int nargs ) {
53          if ( nargs == 2 ) {
54              Object a2 = mc.popObject();
55              Object a1 = mc.popObject();
56              mc.pushObject( apply2( a1, a2 ) );
57          } else {
58              throw(
59                  FunctionAlert.eval(
60                      "Binary function being applied to wrong number of args",
61                      "Binary functions take exactly two arguments"
62                  ).culpritArgs( this, mc, nargs ).mishap()
63              );
64          }
65      }
66  
67      /**
68       * Returns the result of this function when applied to the two specified
69       * arguments.
70       *
71       * @param a1    the first argument to the function
72       * @param a2    the second argument to the function
73       * @return  the result of applying this function to the two arguments
74       */
75      public abstract Object apply2( final Object a1, final Object a2 );
76  
77  }