/**
* Function VisitUnaryExpr
* Param : unary expression to evaluate
* Return : the negated value of the right operand or error
*/
public Value VisitUnaryExpr(Expr.Unary expr)
{
Value right = Evaluate(expr.Right);
/* If the operator is NOT and the right operand is BOOL */
if (expr.OperatorToken.Kind == TokenKind.Not)
{
if (right.Type.Equals(VALTYPE.BOOL))
{
return(new Value(VALTYPE.BOOL, !((bool)right.Val)));
}
/* If the right operand is not BOOL throw an error */
else
{
throw new RuntimeError(expr.OperatorToken, "Trying to negate a non bool value");
}
}
return(null);
}
/**
* Function VisitUnaryExpr : checks that the operator is NOT and
* that the right expression is BOOL. Otherwise throws an error
* Param : unary expression to ckeck
* Return : the type of the unary expression
*/
public VALTYPE VisitUnaryExpr(Expr.Unary expr)
{
VALTYPE right = GetType(expr.Right);
/* If the operator is NOT and the right expr is BOOL */
if (expr.OperatorToken.Kind == TokenKind.Not)
{
if (right.Equals(VALTYPE.BOOL))
{
return(right);
}
/* Error if right expr is not BOOL */
else
{
throw new TypeError(expr.OperatorToken, "'" + expr.OperatorToken.Text
+ "' expects a BOOL expression, got " + right.ToString() + " instead.");
}
}
/* Single operand */
else
{
return(right);
}
}
/**
* Function VisitUnaryExpr
* Param : unary expression to visit
* Return : parenthesized string of the value
*/
public String VisitUnaryExpr(Expr.Unary expr)
{
return(Parenthesize(expr.OperatorToken.Text, expr.Right));
}