ASTNot.java

public class ASTNot implements ASTNode {

    ASTNode exp;

    public ASTNot(ASTNode e)
    {
		exp = e;
    }

    @Override
	public IValue eval(Environment<IValue> e) throws InterpreterError {
        IValue v0 = exp.eval(e);

        if (v0 instanceof VBool) {
            return new VBool(!((VBool)v0).getval());
        } else {
            throw new InterpreterError("illegal type to not operator");
        }
    }

    public ASTType typecheck(Environment<ASTType> e) throws TypeCheckError, InterpreterError {
        ASTType t = exp.typecheck(e);
        if (!(t instanceof ASTTBool))
            throw new TypeCheckError("~: arg type not bool");
        return ASTTBool.tbool;
    }

    @Override
    public boolean isFreeOutsideLambda(String id) {
		return exp.isFreeOutsideLambda(id);
	}
        
}