Weird Error

This is a discussion on Weird Error within the C Programming forums, part of the General Programming Boards category; Hello today i wanted to know like how many strings inside a str * but problem its 1 + orginal ...

  1. #1
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    Weird Error

    Hello today i wanted to know like how many strings inside a str * but problem its 1 + orginal strings and I wanted to make this following code so the str get rand strings only after like 2nd string only but i keep getting weird results as if the thing counted the strings as 7 not 6
    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <time.h>
    char *Names[]= {
        "first",//stops
        "second",//vowels
        "third",
        "fourth","fifth","sixth","seventh"
    };
    int main(void)
    {
        int y;
        srand(time(NULL)); 
        y=  2+ rand() % sizeof (Names) / sizeof(Names[0]);
    
        printf("%d\n",y);
        puts(Names[y]);
        getchar();
        return 0;
    }
    try print
    y= sizeof (Names) / sizeof(Names[0]);
    and it will print 7th character not 6th i know its 7 but arrays start from zero so i dunno how to fix this .....
    and i dunt wanna make it so i have some tests if to test if y==7 --y because that would be lame :P

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    I have no idea what you're asking. sizeof(Names)/sizeof(Names[0]) is 7. This means that when you do %7, you will get either 0, 1, 2, 3, 4, 5, or 6. (You can't have a remainder of 7 when you divide by 7.) So you could use y as an index perfectly, except for the fact that you add two to it....

  3. #3
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    i want the rand to start at 2 not so thats y i added the code to it

  4. #4
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    i want random elements from 2 to 6

  5. #5
    and the Hat of Guessing tabstop's Avatar
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    So if you only want five possibilities, then you have to % by 5, not by 7.

  6. #6
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    but it will start between 0 to 5 not 2 6 it will choose only from strings 0 to 5

  7. #7
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by elwad
    but it will start between 0 to 5 not 2 6 it will choose only from strings 0 to 5
    That is where the addition of 2 comes in. (Besides, it will be from 0 to 4, not 0 to 5).
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  8. #8
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    Quote Originally Posted by laserlight View Post
    That is where the addition of 2 comes in. (Besides, it will be from 0 to 4, not 0 to 5).
    yes but if you see in my code that it types 7 or 8 wrong and if i make it with % output will be 0 like if i made y % 7

  9. #9
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by elwad
    yes but if you see in my code that it types 7 or 8 wrong and if i make it with % output will be 0 like if i made y % 7
    You have not posted your updated code, so I see nothing relevant in code. If you have not updated your code, then read tabstop's post #5 and my post #7 again.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  10. #10
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    yah i fixed it i think
    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <time.h>
    char *Names[]= {
        "first",//stops
        "second",//vowels
        "third",
        "fourth","fifth","sixth","seventh"
    };
    int main(void)
    {
        int y;
        srand(time(NULL)); 
        y=2+rand() % (sizeof (Names) / sizeof(Names[0])-2);
        printf("%d\n",y);
        puts(Names[y]);
        getchar();
        return 0;
    }
    first we + 2 to rand() then after that we minus the number so it get only 5 possiblities is that right ?

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