src/builtin/PRED_tab_2.java

package com.googlecode.prolog_cafe.builtin;
import com.googlecode.prolog_cafe.exceptions.BuiltinException;
import com.googlecode.prolog_cafe.exceptions.ExistenceException;
import com.googlecode.prolog_cafe.exceptions.IllegalDomainException;
import com.googlecode.prolog_cafe.exceptions.PInstantiationException;
import com.googlecode.prolog_cafe.exceptions.PermissionException;
import com.googlecode.prolog_cafe.lang.Arithmetic;
import com.googlecode.prolog_cafe.lang.IntegerTerm;
import com.googlecode.prolog_cafe.lang.JavaObjectTerm;
import com.googlecode.prolog_cafe.lang.NumberTerm;
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;

import java.io.PrintWriter;
/**
   <code>tab/2</code><br>
   @author Mutsunori Banbara (banbara@kobe-u.ac.jp)
   @author Naoyuki Tamura (tamura@kobe-u.ac.jp)
   @version 1.0
*/
public class PRED_tab_2 extends Predicate.P2 {
    public PRED_tab_2(Term a1, Term a2, Operation cont) {
        arg1 = a1;
        arg2 = a2;
        this.cont = cont;
    }

    @Override
    public Operation exec(Prolog engine) {
        engine.setB0();
        Term a1, a2;
        a1 = arg1;
        a2 = arg2;
	int n;
	String s = "";
	Object stream = null;

	// Char
	a2 = a2.dereference(); 
	if (a2 instanceof VariableTerm)
	    throw new PInstantiationException(this, 2);
	if (! (a2 instanceof IntegerTerm)) {
	    try {
		a2 = Arithmetic.evaluate(a2);
	    } catch (BuiltinException e) {
		e.goal = this;
		e.argNo = 2;
		throw e;
	    }
	}
	n = ((NumberTerm)a2).intValue();
	// S_or_a
	a1 = a1.dereference(); 
	if (a1 instanceof VariableTerm) {
	    throw new PInstantiationException(this, 1);
	} else if (a1 instanceof SymbolTerm) {
	    if (! engine.getStreamManager().containsKey(a1))
		throw new ExistenceException(this, 1, "stream", a1, "");
	    stream = ((JavaObjectTerm) engine.getStreamManager().get(a1)).object();
	} else if (a1 instanceof JavaObjectTerm) {
	    stream = ((JavaObjectTerm) a1).object();
	} else {
	    throw new IllegalDomainException(this, 1, "stream_or_alias", a1);
	}
	if (! (stream instanceof PrintWriter))
	    throw new PermissionException(this, "output", "stream", a1, "");
	// tab
	for (int i=0; i<n; i++)
	    s += " ";
	((PrintWriter) stream).print(s);
	return cont;
    }
}