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Describe the purpose rather than just a pointer in the title; removed image of text
Toby Speight
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The solution for the exercise Fold long lines (K&R2 Exercise 1-22 from the book "The C programming language" K&R2)
The solution for the exercise 1-22 from the book "The C programming language" K&R2
Fold long lines (K&R2 Exercise 1-22)
The solution for the exercise 1-22 from the book "The C programming language" K&R2
My solution : https://github.com/AhmedAlaa-10/The-C-programming-language.-k-R-2-solutions-by-me/blob/main/Chap.%201/ex22.c
The key idea is that I process whitespace character by character while processing a sequence of non-blank characters block by block, i.e. I read a block then decide whether to print it in the current line or next line.
#include <stdio.h>
#define LINE_MAX_SIZE 21 /* The maximum number of columns allowed in a single line */
#define IN_NON_BLANK_SEQ 1 /* Indicate that a sequence of non-blank character are being processed */
#define TAP_STOP_DIST 5
#define NON_BLANK(ch) (ch != '\t' && ch != '\n' && ch != ' ')
int get_next_tap_pos(int current_column) {
// columns numbered 0, 1, 2... there is a tap stop at 0, 5, 10, 15, 20
return current_column / TAP_STOP_DIST * TAP_STOP_DIST + TAP_STOP_DIST;
}
int main(void)
{
char block[LINE_MAX_SIZE+1];
int column_pos = 0; /* Indicate the current column in the output where the next character will be printed*/
int index_non_blank = 0; /* Indicate the number of the non-blank char in the next non-blank char sequence */
int state = !IN_NON_BLANK_SEQ; /* Indicate whether a non-blank character is being processed */
int ch;
while ( (ch = getchar()) != EOF) {
if (NON_BLANK(ch)) {
state = IN_NON_BLANK_SEQ;
if (index_non_blank == LINE_MAX_SIZE) {
// There is a word bigger than the size of the line
block[LINE_MAX_SIZE] = '\0';
// Should I print it in the current line or in the next line ?
// Our word is as big as our line. so if current line is not empty, we can't print it here
if (column_pos != 0)
putchar('\n');
printf("%s\n", block);
column_pos = 0;
index_non_blank = 0;
block[index_non_blank] = ch;
}
else {
block[index_non_blank] = ch;
++index_non_blank;
}
}
else {
// Is there a non-blank sequence that just finished ?
if (state == IN_NON_BLANK_SEQ) {
// Should the current word be printed in the current line or next line ?
block[index_non_blank] = '\0';
int expected_column_num = column_pos + index_non_blank;
if (expected_column_num <= LINE_MAX_SIZE) {
printf("%s", block);
column_pos = expected_column_num;
}
else {
putchar('\n');
printf("%s", block);
column_pos = index_non_blank;
}
state = !IN_NON_BLANK_SEQ;
index_non_blank = 0;
}
// now print the whitespace character and update column position
if (ch == '\n') {
putchar(ch);
column_pos = 0;
}
else if (ch == ' ' && column_pos < LINE_MAX_SIZE) {
putchar(ch);
++column_pos;
}
else if (ch == '\t' && column_pos < LINE_MAX_SIZE) {
putchar(ch);
column_pos = get_next_tap_pos(column_pos);
}
else {
putchar('\n');
column_pos = 0;
}
}
}
}
```