Structure help.

This is a discussion on Structure help. within the C Programming forums, part of the General Programming Boards category; Basically, I'm trying to define a structure type and I'm getting a syntax error on the third to last line. ...

  1. #1
    Work in Progress..... Jaken Veina's Avatar
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    Structure help.

    Basically, I'm trying to define a structure type and I'm getting a syntax error on the third to last line.
    Code:
    struct term
    {
     char sign;
     char coef;
     char xvar;
     char yvar;
     char oparen;
     term pterm[5]; //error here
     char cparen;
    };
    Also, on the same line I'm getting,
    [Warning] no semicolon at the end of struct or union
    I read in the tutorial on structures that the syntax for defining a structure type is different in C than C++, but when I comment out that line, it compiles fine. And, I know you can use a variable whose type is the structure you are defining, because it was done in the article on the Huffman compression technique.

    Any thoughts?

    BTW, I'm using the DevC++ compiler.

  2. #2
    Gawking at stupidity
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    Replace:
    Code:
    term pterm[5]; //error here
    with:
    Code:
    struct term pterm[5]; // no error now
    If you understand what you're doing, you're not learning anything.

  3. #3
    char main() RoshanX's Avatar
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    Code:
    struct term
    {
     char sign;
     char coef;
     char xvar;
     char yvar;
     char oparen;
     term pterm[5]; <--------
    };
    <---- The compiler doesn't know the storage requirement for struct term. So it will flag an error.
    The only way around this is,

    Code:
    struct term
    {
     char sign;
     char coef;
     char xvar;
     char yvar;
     char oparen;
     struct term* pterm;  
    };
    This works because, the size of a pointer type is constant ( for that particular OS and architecture ) and known before by the compiler.

  4. #4
    Work in Progress..... Jaken Veina's Avatar
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    Bah. Of course. Thankies.

    Ah, nevermind. More errors. On that same line,
    Code:
    struct term pterm[5];
    I'm now getting the error message,
    field 'pterm' has incomplete type
    But, wait! I changed the variable to a pointer and it works fine. Thanks.

  5. #5
    ATH0 quzah's Avatar
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    Quote Originally Posted by itsme86
    Replace:
    Code:
    term pterm[5]; //error here
    with:
    Code:
    struct term pterm[5]; // no error now
    Yeah except you can't do that. You can't indefinately have one structure contain an actual instance of itself. You can have it store pointers to instances of itself, but you can't have it store actual instances. Why? Well, what happens if you have a recursive function which never ends? Exactly. That's what would happen if you had a structure contain an instance of itself.

    Quzah.
    Hope is the first step on the road to disappointment.

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