L-1 MCS 275 Mon 8 Jan 2001

Below are listings for programs we discussed in class.

/* make a frequency table for floats */

#include <stdio.h>

int main(void)
{
   float x;
   int i;
   int freq[12];
  /* freq[0] counts numbers x for which 0.0 <= x < 0.1,
     freq[1] counts numbers x for which 0.1 <= x < 0.2,
     freq[2] counts numbers x for which 0.2 <= x < 0.3, ... ,
     freq[10] counts numbers x for which 1.0 <= x,
     freq[11] counts numbers x for which x < 0.0. */

   printf("Give sequence of floats :\n");

   for (i=0; i<12; ++i) freq[i] = 0;
   while (scanf("%f", &x) == 1)
   {
      if (x < 0.0)
         ++freq[11];
      else if (x >= 1.0)
         ++freq[10];
      else
      {
         i = 10*x;                        /* type cast truncates */
         ++freq[i];
      }
       
   }  
   printf("The frequency table :\n");
   for (i=0; i<12; ++i) printf("%5d",freq[i]);
   printf("\n");

   return 0;
}

This is the version with pointers, avoiding arrays entirely.


/* make a frequency table for floats, pointer version */

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
   float x;
   int i;
   int *freq, *p;
  /* freq[0] counts numbers x for which 0.0 <= x < 0.1,
     freq[1] counts numbers x for which 0.1 <= x < 0.2,
     freq[2] counts numbers x for which 0.2 <= x < 0.3, ... ,
     freq[10] counts numbers x for which 1.0 <= x,
     freq[11] counts numbers x for which x < 0.0. */

   printf("Give sequence of floats :\n");

   freq = calloc(12, sizeof(int)); 
   while (scanf("%f", &x) == 1)
   {
      if (x < 0.0)
         ++(*(freq+11));
      else if (x >= 1.0)
         ++(*(freq+10));
      else
      {
         i = 10*x;                        /* type cast truncates */
         ++(*(freq+i));
      }
       
   }  
   printf("The frequency table :\n");
   
   p = freq;
   for (i=0; i<12; ++i)
   {
      printf("%5d",*p);
      ++p;
   }
   printf("\n");
   free(freq);

   return 0;
}