Exercise 1-20

Exercise 1-20  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 a symbolic parameter?

For clarity, I have renamed n to TABSTOP.  If the value is known at compile time then a symbolic parameter seems appropriate.  If it is not, then a variable is best.  Perhaps the value could be given on the command line.

#include <stdio.h>

#define TABSTOP 8

int main(void)

{

  int c;

  int col = 0;

  while (c = getchar(), c!=EOF)

  {

    switch(c)

    {

      /* Should also put \r here and a bunch of other cases. */

    case '\n':

      putchar(c);

      col = 0;

      break;

    case '\t':

      do

      {

        putchar(' ');

        col++;

      }

      while(col%TABSTOP);

      break;

    default:

      putchar(c);

      col++;

      break;

    }

  }

  return 0;

}