Random chars in a certain range

This is a discussion on Random chars in a certain range within the C++ Programming forums, part of the General Programming Boards category; I'm trying to generate 1024 random numbers, staying within the first half of the ASCII table (everything < 127) but ...

  1. #1
    Supermassive black hole cboard_member's Avatar
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    Random chars in a certain range

    I'm trying to generate 1024 random numbers, staying within the first half of the ASCII table (everything < 127) but not including anything below 33. Basically I want to stay with characters which are displayable while staying away from the ones which only "display" in a console window.

    The following works, but there is a weird... thing. I can't explain it in more detail other than the number generated is occasionally 3435973836. No matter how I twist this, that number appears no less than 100 times.

    Code:
    int main (int argc, char **argv)
    {
        char    data[1024];
        char    c = 0;
        unsigned debug_data[1024];
    
        memset (data, 0, 1024);
    
        srand ((unsigned) time (0));
    
        for (unsigned i = 0; i < 1024; i++) {
                    c = rand () / (RAND_MAX / 127 + 1);  // stay within lower 127?
                    if (! (c > 33)) continue;
                    key[i] = c;
                    debug_data[i] = (unsigned) c;
        }
    
        return 0;
    }
    I build up debug_data so I can see the ASCII values for each character it outputs. That weird random value appears randomly...

    Is there anything glaringly wrong with it?
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

    - Mike McShaffry

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    and the hat of wrongness Salem's Avatar
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  3. #3
    Supermassive black hole cboard_member's Avatar
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    Thanks buddy
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

    - Mike McShaffry

  4. #4
    Frequently Quite Prolix dwks's Avatar
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    You might want to read Prelude's article on the subject: http://eternallyconfuzzled.com/tuts/random.html
    dwk

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