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Whats wrong with this program?

This is a discussion on Whats wrong with this program? within the C Programming forums, part of the General Programming Boards category; Code: #include <stdio.h> #define TOTAL_ELEMENTS ( sizeof ( array ) / sizeof ( array [ 0 ])) int array [] ...

  1. #1
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    Whats wrong with this program?

    Code:
    #include<stdio.h>
    #defineTOTAL_ELEMENTS (sizeof(array) /sizeof(array[0]))intarray[] = {23,34,12,17,204,99,16};
    intmain()
      {
    intd;
    for(d=-1;d<= (TOTAL_ELEMENTS-2);d++)
    printf("%d\n",array[d+1]);
    return0;
      }


  2. #2
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    You are using an identifier before declaring it.

    Identifiers must be first declared before using them in a function.

  3. #3
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by Swoorup
    Whats wrong with this program?
    According to my compiler:
    Code:
    test.c:2:2: invalid preprocessing directive #defineTOTAL_ELEMENTS
    test.c:4: warning: return type defaults to `int'
    test.c: In function `intmain':
    test.c:5: error: `intd' undeclared (first use in this function)
    test.c:5: error: (Each undeclared identifier is reported only once
    test.c:5: error: for each function it appears in.)
    test.c:6: error: `d' undeclared (first use in this function)
    test.c:6: error: `TOTAL_ELEMENTS' undeclared (first use in this function)
    test.c:7: error: `array' undeclared (first use in this function)
    test.c:8: error: `return0' undeclared (first use in this function)
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  4. #4
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    Sorry the code turned awkward when copying and pasting it.
    This is the one:
    Code:
    #include<stdio.h> 
    #define TOTAL_ELEMENTS (sizeof(array) /sizeof(array[0])) 
    
    
    int array[] = {23,34,12,17,204,99,16};
    int main()
    {
    int d;
    for(d=-1;d <= (TOTAL_ELEMENTS-2);d++)
    printf("%d\n",array[d+1]);
    return 0;
    }
    Still does not work though

  5. #5
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    read the above post.

  6. #6
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    No, it works though if this line
    for(d=-1;d <= (TOTAL_ELEMENTS-2);d++)
    is replace by for(d=0;d <= (TOTAL_ELEMENTS-2);d++)

    I just don't understand why d=-1 does not make the whole program loop and print the elements

  7. #7
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    Dude, you won't get any output even if you change d=-1 to d=0.

  8. #8
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    You don't believe me at all

    if d=0
    this is the output:
    34
    12
    17
    204
    99
    16
    Press any key to continue...

    And with d=-1
    Press any key to continue...

    Please do see for yourself. I had found the code somewhere but forgot where! It was somewhere from a c puzzle like site. But today I just got to stumble across it

  9. #9
    and the hat of wrongness Salem's Avatar
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    > I just don't understand why d=-1 does not make the whole program loop and print the elements
    Because the comparison is int <= size_t

    But since size_t is an unsigned number, the int gets promoted to unsigned as well, resulting in a comparison of
    if ( 0xffffffff <= 6 )
    which is obviously false, and therefore nothing happens.
    Swoorup likes this.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  10. #10
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    So the -1 gets converted to this 4294967295?
    That's really interesting but confusing at the same point.

    Thank you sir.

  11. #11
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    Quote Originally Posted by Swoorup View Post
    You don't believe me at all
    What I believe is that you had a problem and rather than think it over a bit and fix it, you started throwing code at it to see what stuck...

    Code:
    #include<stdio.h> 
    #define TOTAL_ELEMENTS (sizeof(array) /sizeof(array[0])) 
    
    
    int array[] = {23,34,12,17,204,99,16};
    
    int main()
      {
         int d;
         for(d = 0; d < TOTAL_ELEMENTS; d++)
            printf("%d\n", array[d]);
    
         return 0;
      }

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