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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 c, spaces;
spaces = 0;
while ((c = getchar()) != EOF) {
// Make sure the character is a space...
if (c == ' ') {
++spaces;
// When spaces is equal to TABWIDTH, we can add a tab
if (spaces == TABWIDTH) {
putchar('\t');
spaces = 0;
}
} else {
/* As soon as we hit a non-space character, we need to make sure
* there aren't 1-7 spaces leftover. These need to be output before
* we output the non-space character itself! This little loop is
* interesting because it solves the problem of leftover spaces
* _and_ gets the 'spaces' back to zero, which it needs to be once
* we hit a non-space character.
*/
while (spaces != 0) {
putchar(' ');
--spaces;
}
// Output the non-space character.
putchar(c);
}
}
return 0;
}
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