01: /*
02: * Jatha - a Common LISP-compatible LISP library in Java.
03: * Copyright (C) 1997-2005 Micheal Scott Hewett
04: *
05: * This library is free software; you can redistribute it and/or
06: * modify it under the terms of the GNU Lesser General Public
07: * License as published by the Free Software Foundation; either
08: * version 2.1 of the License, or (at your option) any later version.
09: *
10: * This library 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 GNU
13: * Lesser General Public License for more details.
14: *
15: * You should have received a copy of the GNU Lesser General Public
16: * License along with this library; if not, write to the Free Software
17: * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18: *
19: *
20: * For further information, please contact Micheal Hewett at
21: * hewett@cs.stanford.edu
22: *
23: */
24:
25: package org.jatha.compile;
26:
27: import org.jatha.Jatha;
28: import org.jatha.dynatype.*;
29: import org.jatha.machine.*;
30:
31: // According the the CL spec, the value argument of DEFVAR
32: // is only supposed to be evaluated if the argument is going
33: // to be assigned to the variable. This means we have to
34: // evaluate it at runtime, but only if necessary.
35:
36: public class DefvarPrimitive extends LispPrimitive {
37: public DefvarPrimitive(Jatha lisp) {
38: super (lisp, "DEFVAR", 1, 3);
39: }
40:
41: public void Execute(SECDMachine machine) {
42: LispValue args = machine.S.pop();
43: LispValue sym = args.first();
44: LispValue val = args.second();
45:
46: // Declare the symbol as Special
47: sym.set_special(true);
48:
49: // If there is a value and the symbol is not bound,
50: // we need to evaluate the argument and assign it to the symbol.
51: if ((args.basic_length() == 2) && (sym.boundp() == f_lisp.NIL)) {
52: machine.C.pop(); // Pop the DEFVAR
53:
54: machine.C.push(new SetfSymbolValuePrimitive(f_lisp));
55: machine.C.push(new EvalPrimitive(f_lisp));
56: machine.S.push(sym);
57: machine.S.push(val);
58: } else {
59: // Return the symbol
60: machine.S.push(sym);
61:
62: machine.C.pop(); // Pop the DEFVAR
63: }
64:
65: }
66:
67: // Evaluate no args. DEFVAR is a special form.
68: public LispValue CompileArgs(LispCompiler compiler,
69: SECDMachine machine, LispValue args, LispValue valueList,
70: LispValue code) {
71: return compiler.compileConstantArgsLeftToRight(machine, args,
72: valueList, f_lisp.makeCons(machine.LIS, f_lisp
73: .makeCons(args.length(), code)));
74: }
75: }
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