Thread: Problem in solving a character array problem from K&R book

The first step would be to learn how to indent code.

Code:

#include <stdio.h>
#include <stdlib.h>
#define SPACE ' '
#define IN 1
#define OUT 0
#define TAB '\t'

int main(void)
{
  int buffer[50];
  int i;
  int l = 0;
  int m = 0;
  int c;
  int STATE = OUT;
  for (i = 0; i < 49 && (c = getchar()) != 'X' && c != '\n'; ++i) {
    buffer[i] = c;
  }
  buffer[i + 1] = '/0';
  while (buffer[m] != '/0') {
    if (buffer[m] != SPACE) {
      STATE = IN;               //In the word
      l = 0;
      putchar(buffer[m]);       //print the input as output
      m++;
    } else if (buffer[m] == SPACE) {
      STATE = OUT;              //Now outside the word
      if (STATE == OUT) {
        l = l + 1;              //start counting the spaces
        if (l < 5) {            //ignore if number of spaces are less than 5
          putchar(buffer[m]);
          m++;
        } else if (l >= 4) {
          m = m - 4;            //since 5 continuous spaces are detected push array index back
          l = l - 4;            //push offset back
          buffer[m] = TAB;      //insert TAB at appropriate array field
          putchar(buffer[m]);   //stream the output with TAB
          m++;
        }
      }
    }
  }
}

First point, /0 is not the same as \0

Next, you need to count all the spaces before deciding what mix of spaces and tabs to output. So you only do this when you change state from OUT to IN.

Originally Posted by alter.ego

Program is working fine if l < 4 but not when l>4. I've been trying to debug for a while before giving up & looking for clues here.

One helpful tool is to run your program from the commandline with the following:

entab | tr '\t' '$'

Then you can see the actual tab characters in the output as '$' characters. On Windows, the program `tr' with mingw or you can download it from Coreutils Gnuwin32.