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Subject: #if instead of .if
From: asami@cs.berkeley.edu (Satoshi Asami | =?ISO-2022-JP?B?GyRCQHUbKEI=?= =?ISO-2022-JP?B?GyRCOCsbKEIgGyRCOC0bKEI=?=)
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 * I do not have an answer for this, it was something done at CSRG.  It would
 * be a major rework to change it though!

# is already used for comments.  If you don't want to get into trouble
with things like

#if you don't think this is confusing, you are not thinking :p

you can't use #.  See how much trouble the X/imake folks go through
(use XCOMM in their Imakefile, which are replaced with # for Makefile, 
ugh) to avoid this problem.

Satoshi