strange declaration error

This is a discussion on strange declaration error within the C Programming forums, part of the General Programming Boards category; Well, it's strange, in C++ you can declare that type of variables almost any where in the code... I have ...

  1. #1
    Just a Member ammar's Avatar
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    Well, it's strange, in C++ you can declare that type of variables almost any where in the code...

    I have one question:
    If we have a block inside the function can we declare a variable inside that block...

    int main()
    {
    {
    int x;
    }
    return 0;
    }

    Is that OK!
    none...

  2. #2
    template<typename T> threahdead's Avatar
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    strange declaration error

    hi
    something very strange is happening, or im simply blind.
    Code:
    #include<stdio.h>
    
    int main ()
    {
    	printf("whats wrong?");
    	int i;	
    	return 0;
    }
    my compiler doesnt compile it but says that the "Declaration is not allowed here in function main"

    im using Borland C++ 5.5.1 for win32

    whats wrong with this small code? why cant i declare variables in
    main?
    whaaa

  3. #3
    Programming Sex-God Polymorphic OOP's Avatar
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    In C, declarations have to be at the top of functions.

    I think C99 allows declarations anywhere -- as long as you declare before you use, but I'm not sure; I don't usually program in C. If that's the case, then if you get an updated C compiler you might be able to what you were trying to do.

  4. #4
    Registered User Vber's Avatar
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    You're declaring a variable

    after you started the program.
    You can declare a variable outside a function (global variable) or at the start of the function, look:

    Code:
    #include <stdio.h>
    
    /* global var */
    int iGlobal; 
    
    int main(void)
    {
        /* local var */
        int iLocal;
       
        return 0;
        
    }

  5. #5
    template<typename T> threahdead's Avatar
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    darn!
    thanks i was going blind because of python.

  6. #6
    Microsoft. Who? MethodMan's Avatar
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    I dont think this was mentioned, if so I didnt read everything right. If you have a function, all the variables must be declared at the top of that function

    Code:
    void print()
    {
         int i;
         printf("something");
    }
    -MethodMan-

    Your Move:Life is a game, Play it; Life is a challenge, Meet it; Life is an opportunity, capture it.

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  7. #7
    End Of Line Hammer's Avatar
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    >>all the variables must be declared at the top of that function
    No, as said by Salem, local variables must be declared at the top of the code block, not the function.

    So, a very simplistic example would be this:
    Code:
    #include <stdio.h>
    
    int main()
    {
        int i;
        
        for (i = 0; i < 10; i++)
        {
            int j;
            j = i * 10;
            printf ("%d * 10 is %d\n", i, j);
        }
    
        return 0;
    }
    Here, j is declared within the for loop, and therefore it's scope is limited to that code block.

    Is this good programming style? Well, that's another conversation that I'm sure someone will argue to death in a 50 post long thread, but imho, if it suits your needs, use it.
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

  8. #8
    ....
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    #include<stdio.h>

    int main ()
    {
    printf("whats wrong?");
    int i;
    return 0;
    }
    This compiles fine with me, using GCC 3.1. According to C99, the latest C standard, this is valid C. C99, like C++, does not require that all declarations appear at the start of a block.

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