Question

I am a relative beginner with C. I have written what I think is a fairly simple
C program to iterate a variable ‘season’ inside two for-loops. The code compiles
and runs, but ‘season’ is not being tracked correctly. I am hoping someone may be
willing to offer suggestions on how to correct the code.

Below I provide the results I would like, the current C code, and the results that code
is returning.

I would like the following results:

cohort = 1, class = 1, season = 1
cohort = 1, class = 2, season = 1
cohort = 1, class = 3, season = 2
cohort = 1, class = 4, season = 2
cohort = 1, class = 5, season = 3
cohort = 1, class = 6, season = 3

cohort = 2, class = 1, season = 1
cohort = 2, class = 2, season = 2
cohort = 2, class = 3, season = 2
cohort = 2, class = 4, season = 3
cohort = 2, class = 5, season = 3

cohort = 3, class = 1, season = 2
cohort = 3, class = 2, season = 2
cohort = 3, class = 3, season = 3
cohort = 3, class = 4, season = 3

cohort = 4, class = 1, season = 2
cohort = 4, class = 2, season = 3
cohort = 4, class = 3, season = 3

cohort = 5, class = 1, season = 3
cohort = 5, class = 2, season = 3

cohort = 6, class = 1, season = 3

My C code follows immediately below and after that I present the
results returned by the code:

#include <stdio.h>
#include <math.h>
char quit;

main()
{

int mcoht, mclass, season, nmcohts ;
double season2, cohort2, class2 ;

nmcohts = 6 ;

// cohort loop

for (mcoht=1; mcoht <= nmcohts; mcoht++) {

     season = ceil(mcoht/2) ;

  // class loop

  for (mclass=1; mclass <= (nmcohts-(mcoht-1)); mclass++) {

    season2 = season ;
    cohort2 = mcoht  ;
    class2  = mclass ;

    printf("cohort is:  %10.10lf\n", cohort2);
    printf("class  is:  %10.10lf\n", class2);
    printf("season is:  %10.10lf\n", season2);

    // update season (mclass&1) = 0 if mclass even, 1 if mclass is odd 

    if(((mcoht&1) + (mclass&1)) == 1) season = season + 1; 

  } // close class loop

} // close cohort loop

  printf("To close type 'quit' and hit the return key\n");
  printf("               \n");
  scanf("%d", &quit);

return 0;

}

Here are the results returned by the code. Unless I made a mistake
typing the lines below it looks like ‘season’ is correct for the
even-numbered cohorts, but is 1 less than needed with the odd-numbered
cohorts.

Thank you for any suggestions either regarding how to correct the code or how
to improve this post.

cohort = 1, class = 1, season = 0
cohort = 1, class = 2, season = 0
cohort = 1, class = 3, season = 1
cohort = 1, class = 4, season = 1
cohort = 1, class = 5, season = 2
cohort = 1, class = 6, season = 2

cohort = 2, class = 1, season = 1
cohort = 2, class = 2, season = 2
cohort = 2, class = 3, season = 2
cohort = 2, class = 4, season = 3
cohort = 2, class = 5, season = 3

cohort = 3, class = 1, season = 1
cohort = 3, class = 2, season = 1
cohort = 3, class = 3, season = 2
cohort = 3, class = 4, season = 2

cohort = 4, class = 1, season = 2
cohort = 4, class = 2, season = 3
cohort = 4, class = 3, season = 3

cohort = 5, class = 1, season = 2
cohort = 5, class = 2, season = 2

cohort = 6, class = 1, season = 3

I put code-sample quotes around the results only to display them as columns. I do not need the output to be formatted as shown. I simply need ‘season’ to be calculated correctly.

Answer 1

I’m surprised this hasn’t been answered in half an hour…

The problem you’re having with the ceil() function is that you’re using integer operands for the division. The way C does division with operands that are both integral is that it will produce an integer result, truncating any fractional part.

Therefore, 1/2 gives a result of 0, not 0.5.

If you want a floating point result, you need to force at least one of the operands to be floating point. So instead of:

ceil(mcoht/2)

try

ceil(mcoht/2.0)