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From: rob@kaa.eng.ohio-state.edu (Rob Carriere)
Newsgroups: comp.lang.c
Subject: Re: C optimizer
Keywords: C pure function optimization
Message-ID: <1398@quanta.eng.ohio-state.edu>
Date: 15 Feb 89 17:26:58 GMT
References: <515@larry.UUCP> <9648@smoke.BRL.MIL> <36034@bbn.COM>
Sender: news@quanta.eng.ohio-state.edu
Reply-To: rob@kaa.eng.ohio-state.edu (Rob Carriere)
Organization: Ohio State Univ, College of Engineering
Lines: 16

In article <36034@bbn.COM> mesard@BBN.COM (Wayne Mesard) writes:
>  A function which is entirely composed of known "pure" operations*
>  is, itself, pure.
>
>* Where pure operations is defined as functions that produce no side
>effects and return deterministic values, and most operators (excluding
>assignment to dereferenced pointers and globals).  Hint: Sleep(3) would,
>I believe, be labelled "pure" under this definition, so something's
>still missing.

What seems to be missing is the idea that sleep *does* modify
something, namely time.  So formally speaking, your compiler should
consider sleep to have a side effect on a variable called __time.  If
you do that, there's no problem.

SR