blob: ddcdb229cf8a5c581659402ecf00a6dd6b7136c7 [file] [log] [blame]
package com.googlecode.prolog_cafe.builtin;
import com.googlecode.prolog_cafe.exceptions.IllegalDomainException;
import com.googlecode.prolog_cafe.exceptions.IllegalTypeException;
import com.googlecode.prolog_cafe.exceptions.PInstantiationException;
import com.googlecode.prolog_cafe.lang.*;
/**
* <code>arg/3</code><br>
* @author Mutsunori Banbara (banbara@kobe-u.ac.jp)
* @author Naoyuki Tamura (tamura@kobe-u.ac.jp)
* @version 1.0
*/
public class PRED_arg_3 extends Predicate.P3 {
public PRED_arg_3(Term a1, Term a2, Term a3, Operation cont) {
arg1 = a1;
arg2 = a2;
arg3 = a3;
this.cont = cont;
}
public Operation exec(Prolog engine) {
engine.setB0();
Term a1, a2, a3;
a1 = arg1;
a2 = arg2;
a3 = arg3;
Term[] args;
int arity, argNo;
a1 = a1.dereference();
if(a1.isVariable())
throw new PInstantiationException(this, 1);
else if(! a1.isInteger())
throw new IllegalTypeException(this, 1, "integer", a1);
a2 = a2.dereference();
if (a2.isList()) {
args = new Term[2];
args[0] = ((ListTerm)a2).car();
args[1] = ((ListTerm)a2).cdr();
arity = 2;
} else if (a2.isStructure()) {
args = ((StructureTerm)a2).args();
arity = ((StructureTerm)a2).arity();
} else if (a2.isVariable()) {
throw new PInstantiationException(this, 2);
} else {
throw new IllegalTypeException(this, 2, "compound", a2);
}
argNo = ((IntegerTerm)a1).intValue();
if (argNo < 0)
throw new IllegalDomainException(this, 1, "not_less_than_zero", a1);
if (argNo > arity || argNo < 1)
return engine.fail();
if (! a3.unify(args[argNo-1], engine.trail))
return engine.fail();
return cont;
}
}