Assigning values to functions (Newbie)

This is a discussion on Assigning values to functions (Newbie) within the C Programming forums, part of the General Programming Boards category; I have just started learning C and I already have some issues. Code: #include <stdio.h> int binom(int n, int k) ...

  1. #1
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    Assigning values to functions (Newbie)

    I have just started learning C and I already have some issues.

    Code:
    #include <stdio.h>
    
    int binom(int n, int k)
    {
    int result=1;
    int i;
    if(n == k) return 1;
    if(k == 0) return 1;
    for(i=n;i>n-k;i--)
    result=result*i;
    for(i=1;i<=k;++i)
    result=result/i;
    return result;
    }
    
    
    int main(void)
    {
    int bnm;
    int n, k;
    for(n=0;n<10;n++){
    for(k=0;k<=n;k++){
    bnm=binom(n,k);
    printf("%ld ",bnm);
    }
    printf("\n");
    }
    return 0;
    }
    I understand that variables "n" and "k" from "main" and "binom" function are different but does the line:
    Code:
    bnm=binom(n,k);
    mean it will assign "n" value from "main" function to "binom" function? (Same applies to "k")
    I know this is stupid question, and yes I googled it but I havent found a decent answer. Thanks.

  2. #2
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    Quote Originally Posted by turke92 View Post
    does the line:
    Code:
    bnm=binom(n,k);
    mean it will assign "n" value from "main" function to "binom" function? (Same applies to "k")
    What you would say in programming-speak is: n and k are submitted as arguments to binom, and the result is assigned to bnm.

    I know this is stupid question, and yes I googled it but I havent found a decent answer. Thanks.
    If you are unsure what something does, get as many hints as you can and then start playing around to see what happens. If you have a theory about what you think is happening, try to prove and disprove it.

    Finally: LEARN TO INDENT. STARTING NOW. There are a bunch of examples in C for various "indent styles" here:

    Indent style - Wikipedia, the free encyclopedia

    Pick one (variants on K&R or Allman are most popular) and use it! This is an important part of keeping code comprehensible to yourself and others.
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

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    Thanks!
    One more question. I don't understand the logic behind this... In the "main" function we keep incrementing n and k at the same rate until n=9.
    Shouldn't that keep the ratio of n and k equal (n==k) and therefore always return 1?
    I know I got something wrong but I'm not sure what...

  4. #4
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    Quote Originally Posted by turke92 View Post
    Thanks!
    One more question. I don't understand the logic behind this... In the "main" function we keep incrementing n and k at the same rate until n=9.
    Shouldn't that keep the ratio of n and k equal (n==k) and therefore always return 1?
    I know I got something wrong but I'm not sure what...
    If you would learn to indent your code properly you would actually be able to see what is happening...

    Code:
    #include <stdio.h>
    
    int binom(int n, int k)
    {
       int result=1;
       int i;
    
       if(n == k) 
         return 1;
    
       if(k == 0) 
         return 1;
    
       for(i=n;i>n-k;i--)
         result=result*i;
       for(i=1;i<=k;++i)
         result=result/i;
       return result;
    }
    
    
    int main(void)
    {
       int bnm;
       int n, k;
    
       for(n=0;n<10;n++) 
         {
           for(k=0;k<=n;k++)
             {
               bnm=binom(n,k);
               printf("%ld ",bnm);
             }
           printf("\n");
        }
       return 0;
    }
    See it now? the k loop is inside the n loop... for each value of n you call binom with every value of k.

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    So that means that after testing if n<10 is true the program solves the "binom" function and prints it, increments n, goes into a new line, and after all that it looks if k<=n and does the orders in its brackets? I'm sorry if you find it difficult to understand my stupid question regarding this simple issue.

    EDIT: "See it now? the k loop is inside the n loop... for each value of n you call binom with every value of k." I think I speak english well but this statement confused me and hence my even more confusing question.

  6. #6
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    Here try this little code snippet...
    Code:
    #include <stdio.h>
    
    int main (void)
      { int i, j;
    
        for (i = 0; i < 5; i++)
           for (j = 0; j< i; j++)
              printf( " i = %d, j = %d \t",i,j);
    
       getchar();
       return 0;
    }
    Get it now?

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    So initialization of "j" (j = 0) is made every time if the statement "j < i" is false and initialization of "i" is done only once?

  8. #8
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    Quote Originally Posted by turke92 View Post
    So initialization of "j" (j = 0) is made every time if the statement "j < i" is false and initialization of "i" is done only once?
    Initialization is done only at the beginning of a for() loop... any for() loop, every for() loop...

    You have two loops, one running inside the other...
    Look at the way the numbers count up...

    Now apply that to your original code...

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    I got it but I haven't said what I meant right.
    I thought that the value of j stays saved if we get back to the first loop, I didn't know that after we get back to the second loop initialization is made again.

    Thanks for helping!

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    No j is not saved because you don't go back to the outer loop until the inner one is finished and each time you re-enter the inner loop it's starting over... the numerical printout from my example should have demonstrated that very clearly.

  11. #11
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    Like I said, I got it now, but didn't know this when I encountered the code on the 1st post.

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