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#include <stdio.h>
/* The C Programming Language: 2nd Edition
* Exercise 1-21:
* "Write a program `entab` that replaces strings of blanks by the minimum
* number of tabs and blanks to achieve the same spacing. Use the same tab
* stops as for `detab`. When either a tab or a single blank would suffice to
* reach a tab stop, which should be given preference?"
*
* Answer: A blank. A tab character that comes after (tabstop - 1) blanks makes
* little-to-no sense and could mess up alignment in some environments.
*
*/
#define TABWIDTH 8
int main(void) {
int column, c, spaces;
spaces = column = 0;
while ((c = getchar()) != EOF) {
// First thing's first, advance by a column.
column++;
if (c == ' ') {
/* Add to 'spaces' immediately, we'll decide if it needs to be
* output later.
*/
spaces++;
if (column % TABWIDTH == 0 && spaces > 0) {
putchar('\t');
spaces = 0; // No spaces are left when we tab!
}
} else {
/* Be sure to output any leftover spaces when we come across a
* non-space character. This should allow for spaces between words
* that don't fall along the tabstop lines.
*/
while (spaces > 0) {
putchar(' ');
spaces--;
}
// As usual, reset things on a newline.
if (c == '\n') {
column = 0;
spaces = 0;
}
// Now we can output whatever it is.
putchar(c);
}
}
return 0;
}
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