ValueReference.java

package eu.wietsevenema.lang.oberon.interpreter;

import eu.wietsevenema.lang.oberon.exceptions.ImmutableException;
import eu.wietsevenema.lang.oberon.exceptions.TypeMismatchException;
import eu.wietsevenema.lang.oberon.interpreter.values.Value;

public class ValueReference implements Bindable {

	private Value value;
	private boolean constant = false;

	public ValueReference(Value value) {
		assert (value != null);
		this.value = value;
	}

	private ValueReference(Value value, boolean constant) {
		assert (value != null);

		this.constant = constant;
		this.value = value;
	}

	public static ValueReference createConstant(Value value) {
		// Constructors met boolean parameters zijn verwarrend.
		return new ValueReference(value, true);
	}

	public Value getValue() {
		return value;
	}

	/*
	 * Bewust gekozen om constanten niet met subclass op te lossen; is een
	 * violatie van Liskov substitutie principe.
	 */
	public void setValue(Value value) throws TypeMismatchException, ImmutableException {
		if (this.isConstant()) {
			throw new ImmutableException("Setting a constant is not possible.");
		}
		if (this.value.getClass() == value.getClass()) {
			this.value = value;
		} else {
			throw new TypeMismatchException();
		}
	}

	private boolean isConstant() {
		return this.constant;
	}

}