public Operation exec()

in java/com/googlecode/prolog_cafe/builtin/PRED_number_chars_2.java [28:83]
55 lines of code
19 McCabe index (conditional complexity)

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

	a1 = a1.dereference();
	a2 = a2.dereference();
	if (Prolog.Nil.equals(a2))
	    throw new SyntaxException(this, 2, "character_code_list", a2, "");
	if (a1 instanceof VariableTerm) { // number_chars(-Number, +CharList)
	    if (a2 instanceof VariableTerm) {
		throw new PInstantiationException(this, 2);
	    } else if (! (a2 instanceof ListTerm)) {
		throw new IllegalTypeException(this, 2, "list", a2);
	    }
	    StringBuffer sb = new StringBuffer();
	    Term x = a2;
	    while(! Prolog.Nil.equals(x)) {
		if (x instanceof VariableTerm)
		    throw new PInstantiationException(this, 2);
		if (! (x instanceof ListTerm))
		    throw new IllegalTypeException(this, 2, "list", a2);
		Term car = ((ListTerm)x).car().dereference();
		if (car instanceof VariableTerm)
		    throw new PInstantiationException(this, 2);
		if (! (car instanceof SymbolTerm) || ((SymbolTerm)car).name().length() != 1)
		    throw new IllegalTypeException(this, 2, "character", a2);
		sb.append(((SymbolTerm)car).name());
		x = ((ListTerm)x).cdr().dereference();
	    }
	    try {
		if (! a1.unify(new IntegerTerm(Integer.parseInt(sb.toString())), engine.trail))
		    return engine.fail();
		return cont;
	    } catch (NumberFormatException e) {}
	    try {
		if(! a1.unify(new DoubleTerm(Double.parseDouble(sb.toString())), engine.trail))
		    return engine.fail();
		return cont;
	    } catch (NumberFormatException e) {
		throw new SyntaxException(this, 2, "character_code_list", a2, "");
	    }
	} else if (((a1 instanceof IntegerTerm) || (a1 instanceof DoubleTerm))) { // number_chars(+Number, ?CharList)
	    String s = a1.toString();
	    Term y = Prolog.Nil;
	    for (int i=s.length(); i>0; i--) {
		y = new ListTerm(SymbolTerm.create(s.substring(i-1,i)), y);
	    }
	    if (! a2.unify(y, engine.trail) ) 
		return engine.fail();
	    return cont;
	} else {
	    throw new IllegalTypeException(this, 1, "number", a1);
	}
    }