syntax error in my if statement

This is a discussion on syntax error in my if statement within the C Programming forums, part of the General Programming Boards category; Code: if (tax == 1) { price += shippingcost; total = price - (price * TAX_RATE); return total; } I ...

  1. #1
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    syntax error in my if statement

    Code:
    if (tax == 1) {
                price += shippingcost;   
                total = price - (price * TAX_RATE);
                return total;
           }
    I dont know why but its giving me the message "syntax error before '=' token
    for the line total = price - (price * TAX_RATE);. I cant figure it out why am I getting this error? (it is an 80 lined program and commenting this one line out allows it to compile).Thanks

  2. #2
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    Are all the variables defined?

    Also, are you really sure you want to be subtracting the taxes?

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    What do you mean? I use that same variable total in another if statement right after this one.
    Code:
    if (tax == 1) {
                price += shippingcost;   
                total = price - (price * TAX_RATE);
                return total;
           }
        
           else if (tax == 0){
                total = price + shippingcost;
                return total;
           }
    The use of total in the else if statement doesn't produce any error.

    Oh I see what you mean about the taxes lol I changed it to
    Code:
    total = price + (price * TAX_RATE);
    but it does nothing to fix the compiling error.
    Last edited by UCFuser; 04-01-2011 at 09:50 AM.

  4. #4
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    Quote Originally Posted by UCFuser View Post
    What do you mean? I use that same variable total in another if statement right after this one.
    Code:
    if (tax == 1) {
                price += shippingcost;   
                total = price - (price * TAX_RATE);
                return total;
           }
        
           else if (tax == 0){
                total = price + shippingcost;
                return total;
           }
    The use of total in the else if statement doesn't produce any error.

    Oh I see what you mean about the taxes lol I changed it to
    Code:
    total = price + (price * TAX_RATE);
    but it does nothing to fix the compiling error.
    If it's not too long, post your whole code... or at least enough that we can see the variable declarations and the lines preceding what you've already provided. The error you're getting can also be caused by bracketing errors in earlier code...

  5. #5
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    How do you define TAX_RATE?

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    Good idea... bracketing issue. Or bizarre macros that look like normal code. Or 'shippingcost' is a function or whatever. Or there is a garbagey character in the source/text file that's not visible.

    Yeah, Bayint Naung. TAX_RATE could be a #define with unbalanced parenthesis.

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    This is the whole function

    Code:
    double itemshipping(double price, double weight, int quantity, int tax) {
         
         //declare some intitail variables.    
         double shippingweight, shippingcost, total;
         
         //calculate original cost before shipping costs are added. 
         //find out total cost of shipping. 
         price *= quantity;
         shippingweight = weight * (double)quantity;
        
    
         //setup logic statements to recognize how much to charge per pound for shipping
         if (weight <10)
              shippingcost = shippingweight * 4.00;
           
           else if (weight >=10 && weight <30)
                shippingcost = shippingweight * 2.5;
           
           else if (weight >=30 && weight <50)
                shippingcost = shippingweight * 1.5;
           
           else 
                shippingcost = shippingweight *.99;
        
           //setup logic statements to recognize whether 
           //an item is taxed or not and apply this to 
           //the final cost with the cost of shipping added in. 
           if (tax == 1) {
                price += shippingcost;   
                //total = price + (price * TAX_RATE);
                return total;
           }
        
           else if (tax == 0){
                total = price + shippingcost;
                return total;
           }
    }
    This is the whole function

    this is how TAX_RATE is defined
    Code:
    #define TAX_RATE = 0.065
    Also if it were a bracket error shouldn't I still get an error message when trying to compile after commenting out the bad line?

  8. #8
    C++ Witch laserlight's Avatar
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    The macro is indeed the problem. You should have written:
    Code:
    #define TAX_RATE 0.065
    Otherwise, after macro replacement, your code actually looks like this:
    Code:
    total = price + (price * = 0.065);
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    Ahh I see what you mean, thanks!

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    Code:
                //total = price + (price * TAX_RATE);
    If there is no space between * and TAX_RATE.
    It will become
    total = price + ( price *= 0.065);
    Which is valid no compiler error. But undefined behaviour!!

  11. #11
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by Bayint Naung
    If there is no space between * and TAX_RATE.
    It will become
    total = price + ( price *= 0.065);
    Which is valid no compiler error. But undefined behaviour!!
    My experiments show that that is not correct: I do get a compiler error, meaning that the separate tokens were not combined into one token.
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    Bayint Naung said IF there is no space. IF the programmer had used (price *TAX_RATE);

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    Yes, laserlight, you are right. I've compiled with gcc and I did get compiler error.
    But using -traditional-cpp flag, I was able to compile. Currently I could not find what the standard says about it.
    But most likely I might be wrong.
    Probably Adak turbo C should be able to compile cleanly.

  14. #14
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    I get results like laserlight. I can do
    Code:
    total = price + ( price *= 0.065);
    And I get the following warning:
    $ gcc -Wall foo.c
    foo.c: In function ‘main’:
    foo.c:9: warning: operation on ‘price’ may be undefined
    But if I do
    Code:
    #define TAX_RATE = 0.065
    ...
    total = price + (price *TAX_RATE);
    I get the following:
    Code:
    $ gcc -Wall foo.c
    foo.c: In function ‘main’:
    foo.c:9: error: expected expression before ‘=’ token
    
    $ gcc -E foo.c
    ...
    int main(void)
    {
        double total, price = 1.1;
    
        total = price + (price * = 0.065);
    Notice that the preprocessor inserts a space between * and TAX_RATE . I seem to remember reading this somewhere, but I don't know if it's in the GCC docs or standard somewhere. I believe this is done on purpose, to avoid exactly the problem we're discussing.

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