public string visit(BinOp node)
{
int left = Convert.ToInt32(node.left.accept(this));
int right = Convert.ToInt32(node.right.accept(this));
int result = 0;
switch (node.token.type)
{
case Tokens.PLUS:
result = left + right;
break;
case Tokens.MINUS:
result = left - right;
break;
case Tokens.MUL:
result = left * right;
break;
case Tokens.DIV:
result = left / right;
break;
case Tokens.LT:
result = bool2int(left < right);
break;
case Tokens.GT:
result = bool2int(left > right);
break;
case Tokens.GEQ:
result = bool2int(left >= right);
break;
case Tokens.LEQ:
result = bool2int(left <= right);
break;
case Tokens.ISEQ:
result = bool2int(left == right);
break;
case Tokens.NEQ:
result = bool2int(left != right);
break;
case Tokens.AND:
result = bool2int(left != 0 && right != 0);
break;
case Tokens.OR:
result = bool2int(left != 0 || right != 0);
break;
}
return(Convert.ToString(result));
}
//orexpr : compexpr ((AND) compexpr)*
private AST andexpr()
{
AST node = compexpr();
while (current_token.type == Tokens.AND)
{
Token t = current_token;
eat(Tokens.AND);
node = new BinOp(node, t, compexpr());
}
return(node);
}
//orexpr : andexpr ((OR) andexpr)*
private AST orexpr()
{
AST node = andexpr();
while (current_token.type == Tokens.OR)
{
Token t = current_token;
eat(Tokens.OR);
node = new BinOp(node, t, andexpr());
}
return(node);
}
//mulexpr : factor ((MUL|DIV) factor)*
private AST mulexpr()
{
AST node = factor();
Tokens[] addition_operators = new Tokens[] { Tokens.MUL, Tokens.DIV };
while (Array.IndexOf(addition_operators, current_token.type) != -1)
{
Token t = current_token;
eat(current_token.type);
node = new BinOp(node, t, factor());
}
return(node);
}
//sumexpr : mulexpr ((PLUS|MINUS) mulexpr)*
private AST sumexpr()
{
AST node = mulexpr();
Tokens[] addition_operators = new Tokens[] { Tokens.PLUS, Tokens.MINUS };
while (Array.IndexOf(addition_operators, current_token.type) != -1)
{
Token t = current_token;
eat(current_token.type);
node = new BinOp(node, t, mulexpr());
}
return(node);
}