Function-types: compatability, and typedefs

[Chris Torek]

>In article <19361 at mimsy.UUCP> I wrote:
>>... the answers FOR THIS PARTICULAR CASE are `yes' and `yes'.
>> 	int (*)(void *, void *)		[qsort compare function]
>> and	int (*)(char *, char *)		[strcmp]

In article <1996 at munnari.oz.au> ok at cs.mu.oz.au (Richard O'Keefe) writes:
>If you want to sort an array of strings ... **don't** try to pass
>'strcmp' as the fourth argument of qsort(). ...  What you need is
>    int strptrcmp(char **s1, char **s2)
>	{ return strcmp(*s1, *s2); }

Oops, quite right.  I got tied up in the `do the two function types match'
question and never noticed the fact that qsort is passing pointers to
the objects (here pointers to char *), rather than to that to which the
objects point.

>Did you know that C.A.R.Hoare pointed out in 1962 that Quicksort does
>1.4 times as many comparisons as [the number done by merge sort]?
>He should know: he invented it.

Yes, but everyone likes to analyse Quicksort. :-)  That is, I think
the reason it is used so often is, well, because it is used so often.
(Familiarity breeds distemper, or something like that :-/ )
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris at mimsy.umd.edu	Path:	uunet!mimsy!chris