Path: utzoo!utgpu!news-server.csri.toronto.edu!dgp.toronto.edu!flaps
Newsgroups: comp.lang.c
From: flaps@dgp.toronto.edu (Alan J Rosenthal)
Subject: Re: Order of evalution of expressions.
Message-ID: <1990Sep18.173551.12941@jarvis.csri.toronto.edu>
References: <6398@castle.ed.ac.uk>
Date: 18 Sep 90 21:35:51 GMT
Lines: 17

elee24@castle.ed.ac.uk (H Bruce) writes:
>Is the line
>
>value = *ptr - *ptr++;
>
>sensible C ?

absolutely not.

>Would the following lines be optimized by a compiler (so that value is
>not loaded twice) ?
>
>value = *ptr;
>value -= *ptr++;

quite often, but no non-machine-specific language definition can guarantee you
that.  but they're the best.