Thread: Kernigan and Ritchie Exercise 5-11

Here is the description: Modify the program detab (written as exercises in Chapter 1) to accept a list of tab stops as arguments. Use the default tab settings if there are no arguments.

What I know about tabs, when I hit a tab I travel to the next tab stop. For example, assume tab stops (8, 16, 24, 32) etc so if I'm in column 12 and hit a tab stop I go to column 16. That is, what this exercise is looking for I assume.

Just now I'm having hard time figuring out how should I do this, any pseudocode/other help is appreciated.

Here is my version of detab, by the way, if it is any help here:

Code:

#include <stdio.h>
#define MAXLINE 1000
#define SPACE  ' '
#define TAB  '\t'


/* Write a program detab that replaces tabs in the input
with the proper number of blanks to space to the next tab stop. 
Assume a fixed set of tab stops, say every n columns. Should n be
a variable or symbolic constant? */


int countspaces(int offset, int tabsize)
{


  return tabsize - (offset % tabsize);
   
}




int main(void)


{
  
  int pos, c;


  while((c = getchar()) != EOF)
  {
    
    
  
  if(c == TAB) 
        {
            int numSpaces = countspaces(pos, 5);   /* n is a symbolic constant here, not a variable */
            for(int i = 0; i < numSpaces; ++i)
            {
                putchar(SPACE);
                ++pos;
            }
        }
        
    else if( c == '\n')
        {
         
          putchar(c);
          pos = 0;
          
        }
        
    else
      {
         putchar(c);
         ++pos;
      }
   }
  
}

Thank you @Salem. Can you be more detailed about the code that should be written? It's a bit of time I have written the above code, and my C programming is also rusty (Not to mention the breaks that I have kept from time to time).