From 71eee1204d279fe7590d940a08423e3362609474 Mon Sep 17 00:00:00 2001
From: zlg <zlg@zlg.space>
Date: Thu, 8 Aug 2013 06:35:27 -0500
Subject: Solve Exercise 4-14: Swap Macro
Thanks to ##c on Freenode for helping me understand what the text
didn't clarify.
---
ch4/4-14_swap-macro.c | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
create mode 100644 ch4/4-14_swap-macro.c
diff --git a/ch4/4-14_swap-macro.c b/ch4/4-14_swap-macro.c
new file mode 100644
index 0000000..ac2f102
--- /dev/null
+++ b/ch4/4-14_swap-macro.c
@@ -0,0 +1,30 @@
+#include <stdio.h>
+
+/* The C Programming Language: 2nd Edition
+ *
+ * Exercise 4-14: Define a macro swap(t,x,y) that interchanges two arguments
+ * of type t. (Block structure will help.)
+ *
+ * Answer: Macros are read and processed before syntax is, so you can turn
+ * a macro into shorthand code; more shorthand than functions sometimes.
+ *
+ * This macro assumes x and y are of t type. If the types don't match up,
+ * it'll (probably) break.
+ */
+
+#define swap(t, x, y) {\
+ t z;\
+ z = x;\
+ x = y;\
+ y = z;\
+}
+
+int main() {
+ int a = 3;
+ int b = 7;
+
+ printf("a is %d, b is %d\n", a, b);
+ swap(int, a, b);
+ printf("Now swap, and... a is %d and b is %d!\n", a, b);
+ return 0;
+}
--
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