expressions and #if

[guy at rlgvax.UUCP]

"defined" is given in the System V documentation for "cpp" (along with
__FILE__ and __LINE__; anybody for a "used, but not documented" error
message from "lint"? :-)  They've been around since V7, and the "assert.h"
include file depends on __FILE__ and __LINE__).  I suspect it may have made
it into C language references later than the one issued in K&R.  All three
of those features, I believe, first entered C in V7; the C preprocessor was
completely rewritten, making it considerably faster (I verified the figures
John Reiser - the author of the V7 preprocessor - quotes for speed improvement
a while ago) and adding those features.

	Guy Harris
	{seismo,ihnp4,allegra}!rlgvax!guy