New implementation of 42

42.c

@@ -1,10 +1,21 @@
 #include <stdio.h>
 
+#if defined ORIGINAL
+/* retained for literary criticism */
 #define SIX 1+5
 #define NINE 8+1
+#elif ! defined INSANE
+/* a sensible reimplementation */
+#define SIX 3+3
+#define NINE 15-6
+#else
+/* a less sensible reimplementation */
+#define SIX 24-18
+#define NINE 1/-2+9
+#endif
 
 int main(void)
 {
-    printf("%d * %d = %d\n", SIX, NINE, SIX * NINE);
+    printf("%d × %d = %d\n", SIX, NINE, SIX * NINE);
     return 0;
 }

README.md

@@ -8,24 +8,24 @@ around each reference to a macro parameter, and around the entire definition.
 The reason is that macro expansion works on sequences of tokens.
 The C preprocessor doesn't deal with high-level C syntax.
 
-In the example, the macro `SIX` expands to the token sequence `1 + 5`,
-and the macro `NINE` expands to `8 + 1`.  If each of these expressions
+In the example, unless `ORIGINAL` is defined, the macro `SIX` expands to the token sequence `3 + 3`,
+and the macro `NINE` expands to `15 - 6`.  If each of these expressions
 were evaluated on its own, the results would be 6 and 9, respectively,
 But when they're combined in the expression `SIX * NINE`, the expansion is:
 
-    1+5*8+1
+    3+3*15-6
 
 which is equivalent to:
 
-    1+(5*8)+1
+    3+(3*15)-6
 
 or 42.
 
 The program is also a reference to [a joke](http://en.wikipedia.org/wiki/Phrases_from_The_Hitchhiker%27s_Guide_to_the_Galaxy#Answer_to_the_Ultimate_Question_of_Life.2C_the_Universe.2C_and_Everything_.2842.29) in The Hitchhiker's Guide to the Galaxy, by Douglas Adams.
 
 -- Keith Thompson <Keith.S.Thompson@gmail.com> Tue 2011-11-01
 
-I posted this program to comp.lang.c on Mon 2003-09-29
+Based on a program I posted to comp.lang.c on Mon 2003-09-29
 with this comment:
 
 > (Not original; I don't remember where I got it.)