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-rw-r--r--1-20_detab.c16
-rw-r--r--1-21_entab.c45
2 files changed, 56 insertions, 5 deletions
diff --git a/1-20_detab.c b/1-20_detab.c
index 3101610..e1549e6 100644
--- a/1-20_detab.c
+++ b/1-20_detab.c
@@ -5,11 +5,15 @@
* "Write a program `detab` that replaces tabs in the input with the proper
* number of blanks to space to the next tabstop. Assume a fixed set of
* tabstops, say every 'n' columns. Should 'n' be a variable or a symbolic
- * parameter?
+ * parameter?"
*
* Answer: 'n' should be a symbolic parameter. It's more apparent what's being
* worked with and it's not susceptible to scope. Though, in this simple
* program it really doesn't matter.
+ *
+ * To be correct, this file should use the isprint() function to ensure that
+ * 'column' only gets incremented when a printable character is being read. I'll
+ * come back to this when I learn more of the stdlib.
*/
#define TABWIDTH 8
@@ -30,12 +34,14 @@ int main(void) {
++column;
}
} else {
- // non-tabs simply get output.
- putchar(c);
- ++column;
- // Line-endings should reset the column counter after being output.
if (c == '\n') {
+ // Line-endings should reset the column counter after being output.
+ putchar(c);
column = 0;
+ } else {
+ // Now we can just output and increase column!
+ putchar(c);
+ ++column;
}
}
}
diff --git a/1-21_entab.c b/1-21_entab.c
new file mode 100644
index 0000000..595f583
--- /dev/null
+++ b/1-21_entab.c
@@ -0,0 +1,45 @@
+#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);
+ }
+ }
+}