[REBOL] if/else vs. either
From: joel::neely::fedex::com at: 23-Jul-2001 18:04
Hi, Allen (and all)
<note>
I've been out camping in the mountains for a week, so I'm still
playing catch-up on megabytes of email. If I fail to reply to
something, please put it down to oversight rather than rudeness
or disinterest!
</note>
Following up on an idea from Allen, I ran the following quick-
and-dirty tests with mildly interesting (but not too surprising)
results.
Taking some relatively trivial block, such as
deed: [a: a + 1]
or even
deed: [a: 17]
we can evaluate it a few hundred million times in different ways
to discover the following approximate relative timings. (Due
to coarse-grained timing jitter and overall system workload,
results are rounded to the nearest 10%.)
Relative
Overhead
Expression Required
---------- --------
do deed 100%
if true deed 130%
either true deed [] 150%
either false [] deed 150%
if/else true deed [] 170%
if/else false [] deed 170%
The timing calculations subtracted the base workload before
figuring the ratios, so that the comparison is just for the
control functions themselves. Different numbers of cycles
and different expressions will vary the timings somewhat, but
these figures (+/- 10%) appear to be relatively typical.
Conclusion: Use EITHER instead of IF/ELSE unless writing for
people who are addicted to TLTMNBN! ;-)
-jn-
--
This sentence contradicts itself -- no actually it doesn't.
-- Doug Hofstadter
joel<dot>neely<at>fedex<dot>com
