K&R2 Exercise 1-21

1-21.c

/*K&R2 Exercise 1-21 "entab"*/
#include <stdio.h>

#define TABSTOP 8

int mod(int, int);

int main()
{
	int c, sc, col;
	sc = 0;
	for(col = 1; (c = getchar()) != EOF; ++col){
		if(c == ' '){
			++sc;
			if(mod(col, TABSTOP) == 0){
				putchar('\t');
				sc = 0;
			}			
		}
		else{
			if(sc > 0)
				for(; sc > 0; --sc)
					putchar(' ');
			if(c == '\n')
				col = 0;
			putchar(c);
		}	
	}
}

int mod(int dividend, int divisor)
{
	return dividend - (dividend/divisor * divisor);
}