object IVisitor <object> .visit(BinOpNode node)
{
Node left = node.getLeft();
Node right = node.getRight();
// decorate
left.type = Convert.ToString(left.accept(this));
right.type = Convert.ToString(right.accept(this));
if (left.type == Token.INT && right.type == Token.INT)
{
node.type = Token.INT;
}
else if (left.type == Token.STRING || right.type == Token.STRING)
{
node.type = Token.STRING;
}
else if (left.type == Token.BOOL || right.type == Token.BOOL)
{
node.type = Token.BOOL;
}
checkOperationIsAllowed(node, left, right);
return(node.type);
}
object IVisitor <object> .visit(BinOpNode node)
{
object left = evaluate(node.getLeft());
object right = evaluate(node.getRight());
switch (node.value)
{
case "+":
// concatenation
if (node.getLeft().type.Equals(Token.STRING) & node.getRight().type.Equals(Token.STRING))
{
return(left.ToString() + right.ToString());
}
else
{
return(Convert.ToInt32(left) + Convert.ToInt32(right));
}
case "-":
return(Convert.ToInt32(left) - Convert.ToInt32(right));
case "*":
return(Convert.ToInt32(left) * Convert.ToInt32(right));
case "/":
return(Convert.ToInt32(left) / Convert.ToInt32(right));
case "=":
if (node.getLeft().type.Equals(Token.STRING) & node.getRight().type.Equals(Token.STRING))
{
return(left.ToString().Equals(right.ToString()));
}
else
{
return(Convert.ToInt32(left) == Convert.ToInt32(right));
}
case "<":
if (node.getLeft().type.Equals(Token.STRING) & node.getRight().type.Equals(Token.STRING))
{
return(left.ToString().Length < right.ToString().Length);
}
else
{
return(Convert.ToInt32(left) < Convert.ToInt32(right));
}
case "&":
return(Convert.ToBoolean(left) & Convert.ToBoolean(right));
default:
break;
}
return(null);
}
private Node expr()
{
Node left = term();
while (currentToken.type == Token.ADD | currentToken.type == Token.SUB)
{
Node node = new BinOpNode(currentToken);
nextToken();
node.addChild(left);
node.addChild(term());
left = node;
}
return(left);
}
private Node term()
{
Node left = factor();
while (currentToken.type == Token.MUL | currentToken.type == Token.DIV | currentToken.type == Token.LT | currentToken.type == Token.AND | currentToken.type == Token.EQ)
{
Node node = new BinOpNode(currentToken);
nextToken();
node.addChild(left);
node.addChild(factor());
left = node;
}
return(left);
}
object IVisitor <object> .visit(BinOpNode node)
{
return(null);
}