/*
* Jatha - a Common LISP-compatible LISP library in Java.
* Copyright (C) 1997-2005 Micheal Scott Hewett
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*
* For further information, please contact Micheal Hewett at
* hewett@cs.stanford.edu
*
*/
package org.jatha.machine;
import org.jatha.Jatha;
import org.jatha.dynatype.LispValue;
// @date Sat Feb 1 22:18:53 1997
/**
* opSEL takes a branch in an IF-ELSE expression.
* It selects code from the C register and, depending on
* whether the topmost value in the S register is true
* or not, places that code on the C register and pushes
* the remaining C register code onto the D register.
* Pops the S register.
* @see SECDMachine
* @author Micheal S. Hewett hewett@cs.stanford.edu
*/
class opSEL extends SECDop
{
/**
* It calls <tt>SECDop()</tt> with the machine argument
* and the label of this instruction.
* @see SECDMachine
*/
public opSEL(Jatha lisp)
{
super(lisp, "SEL");
}
public void Execute(SECDMachine machine)
{
LispValue selector = machine.S.pop();
LispValue trueCodeBranch;
LispValue falseCodeBranch;
machine.C.pop(); // Pop the SEL command.
trueCodeBranch = machine.C.pop();
falseCodeBranch = machine.C.pop();
machine.D.push(machine.C.value()); // push remaining code.
if (selector == f_lisp.NIL)
machine.C.assign(falseCodeBranch);
else
machine.C.assign(trueCodeBranch);
}
public LispValue grindef(LispValue code, int indentAmount)
{
indent(indentAmount);
System.out.print(functionName);
f_lisp.NEWLINE.internal_princ(System.out);
printCode(code.second(), indentAmount + 8);
f_lisp.NEWLINE.internal_princ(System.out);
printCode(code.third(), indentAmount + 8);
f_lisp.NEWLINE.internal_princ(System.out);
return code.cdr().cdr().cdr();
}
}