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authorzlg <zlg@zlg.space>2012-11-22 06:42:57 -0600
committerzlg <zlg@zlg.space>2012-11-22 06:42:57 -0600
commitf1a978269ad2c39aa6d02acbb3e199a33a369fb2 (patch)
treed0e3ce8adaf3367ddc650c78c5115750b1bfa563
parentSolve exercise 1.19: Reverse each line of input (diff)
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Solve exercise 1.20: Detab
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diff --git a/1-20_detab.c b/1-20_detab.c
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+#include <stdio.h>
+
+/* The C Programming Language: 2nd Edition
+ * Exercise 1-20:
+ * "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?
+ *
+ * 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.
+ */
+
+#define TABWIDTH 8
+
+int main(void) {
+ int column, c;
+ column = 0;
+ while ((c = getchar()) != EOF) {
+ // Be sure that the character is a tab
+ if (c == '\t') {
+ /*
+ * Divide a line by TABWIDTH and you have your tabstops. If you
+ * modulo by TABWIDTH and it equals 0, you've reached a tabstop and
+ * don't need to output more spaces!
+ */
+ while (column % TABWIDTH != 0 && column != 0) {
+ putchar(' ');
+ ++column;
+ }
+ } else {
+ // non-tabs simply get output.
+ putchar(c);
+ ++column;
+ // Line-endings should reset the column counter after being output.
+ if (c == '\n') {
+ column = 0;
+ }
+ }
+ }
+ return 0;
+}