src/builtin/PRED_$hash_remove_first_3.java

package com.googlecode.prolog_cafe.builtin;
import com.googlecode.prolog_cafe.exceptions.ExistenceException;
import com.googlecode.prolog_cafe.exceptions.IllegalDomainException;
import com.googlecode.prolog_cafe.exceptions.InternalException;
import com.googlecode.prolog_cafe.exceptions.PInstantiationException;
import com.googlecode.prolog_cafe.lang.HashtableOfTerm;
import com.googlecode.prolog_cafe.lang.IntegerTerm;
import com.googlecode.prolog_cafe.lang.JavaObjectTerm;
import com.googlecode.prolog_cafe.lang.ListTerm;
import com.googlecode.prolog_cafe.lang.Operation;
import com.googlecode.prolog_cafe.lang.Predicate;
import com.googlecode.prolog_cafe.lang.Prolog;
import com.googlecode.prolog_cafe.lang.SymbolTerm;
import com.googlecode.prolog_cafe.lang.Term;
import com.googlecode.prolog_cafe.lang.VariableTerm;
/**
   <code>'$hash_remove_first'/3</code><br>
   @author Mutsunori Banbara (banbara@kobe-u.ac.jp)
   @author Naoyuki Tamura (tamura@kobe-u.ac.jp)
   @version 1.0
*/
class PRED_$hash_remove_first_3 extends Predicate.P3 {
    public PRED_$hash_remove_first_3(Term a1, Term a2, Term a3, Operation cont) {
        arg1 = a1;
        arg2 = a2;
        arg3 = a3;
        this.cont = cont;
    }

    @Override
    public Operation exec(Prolog engine) {
        engine.setB0();
        Term a1, a2, a3;
        a1 = arg1;
        a2 = arg2;
        a3 = arg3;

	Object hash = null;

	a1 = a1.dereference();
	if (a1 instanceof VariableTerm) {
	    throw new PInstantiationException(this, 1);
	} else if (a1 instanceof SymbolTerm) {
	    if (! engine.getHashManager().containsKey(a1))
		throw new ExistenceException(this, 1, "hash", a1, "");
	    hash = ((JavaObjectTerm) engine.getHashManager().get(a1)).object();
	} else if (a1 instanceof JavaObjectTerm) {
	    hash = ((JavaObjectTerm) a1).object();
	} else {
	    throw new IllegalDomainException(this, 1, "hash_or_alias", a1);
	}
	if (! (hash instanceof HashtableOfTerm))
	    throw new InternalException(this + ": Hash is not HashtableOfTerm");
	a2 = a2.dereference();
	Term elem = ((HashtableOfTerm) hash).get(a2);
	if (elem == null || Prolog.Nil.equals(elem))
	    return cont;
	a3 = a3.dereference();
	Term x  = elem;
	Term x0 = Prolog.Nil;
	Term y,z;
	while(! Prolog.Nil.equals(x)) {
	    if (! (x instanceof ListTerm))
		throw new InternalException(this + ": the valus of " + a2 + " is not list structure");
	    y = ((ListTerm)x).car().dereference();
	    z = ((ListTerm)x).cdr().dereference();
	    if (y.equals(a3)) {
		if (Prolog.Nil.equals(z)) {
		    if (x0 instanceof ListTerm)
			((ListTerm)x0).setCdr(Prolog.Nil);
		    else 
			elem = Prolog.Nil;
		} else {
		    ((ListTerm)x).setCar(((ListTerm)z).car().dereference());
		    ((ListTerm)x).setCdr(((ListTerm)z).cdr().dereference());
		}
		break;
	    }
	    x0 = x;
	    x = z;
	}
	if (Prolog.Nil.equals(elem) && a2 instanceof IntegerTerm) {
	    ((HashtableOfTerm)hash).remove(a2);
	    //	    System.out.println("################ key " + a2 + " is removed");
	} else {
	    ((HashtableOfTerm) hash).put(a2, elem);
	}
        return cont;
    }
}