Add license file, reorganize project

1 files changed, 57 insertions, 0 deletions

diff --git a/ch1/1-21_entab.c b/ch1/1-21_entab.c
new file mode 100644
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--- /dev/null
+++ b/ch1/1-21_entab.c
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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;
+}