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.machine;
26:
27: import org.jatha.Jatha;
28: import org.jatha.dynatype.LispValue;
29:
30: // @date Sat Feb 1 22:18:53 1997
31: /**
32: * opSEL takes a branch in an IF-ELSE expression.
33: * It selects code from the C register and, depending on
34: * whether the topmost value in the S register is true
35: * or not, places that code on the C register and pushes
36: * the remaining C register code onto the D register.
37: * Pops the S register.
38: * @see SECDMachine
39: * @author Micheal S. Hewett hewett@cs.stanford.edu
40: */
41: class opSEL extends SECDop {
42: /**
43: * It calls <tt>SECDop()</tt> with the machine argument
44: * and the label of this instruction.
45: * @see SECDMachine
46: */
47: public opSEL(Jatha lisp) {
48: super (lisp, "SEL");
49: }
50:
51: public void Execute(SECDMachine machine) {
52: LispValue selector = machine.S.pop();
53: LispValue trueCodeBranch;
54: LispValue falseCodeBranch;
55:
56: machine.C.pop(); // Pop the SEL command.
57: trueCodeBranch = machine.C.pop();
58: falseCodeBranch = machine.C.pop();
59:
60: machine.D.push(machine.C.value()); // push remaining code.
61:
62: if (selector == f_lisp.NIL)
63: machine.C.assign(falseCodeBranch);
64: else
65: machine.C.assign(trueCodeBranch);
66: }
67:
68: public LispValue grindef(LispValue code, int indentAmount) {
69: indent(indentAmount);
70:
71: System.out.print(functionName);
72: f_lisp.NEWLINE.internal_princ(System.out);
73:
74: printCode(code.second(), indentAmount + 8);
75: f_lisp.NEWLINE.internal_princ(System.out);
76:
77: printCode(code.third(), indentAmount + 8);
78: f_lisp.NEWLINE.internal_princ(System.out);
79:
80: return code.cdr().cdr().cdr();
81: }
82: }
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