Xref: utzoo comp.object:582 comp.lang.c++:5802
Path: utzoo!attcan!utgpu!watserv1!watdragon!gvcormack
From: gvcormack@watdragon.waterloo.edu (Gordon V. Cormack)
Newsgroups: comp.object,comp.lang.c++
Subject: Re: (Very) Dymanic Typing (Was: Dumb question)
Message-ID: <19045@watdragon.waterloo.edu>
Date: 6 Dec 89 14:44:04 GMT
References: <61737@aerospace.AERO.ORG> <9938@june.cs.washington.edu> <1989Dec5.195643.13592@sjsumcs.sjsu.edu>
Organization: U of Waterloo, Ontario
Lines: 36

In article <1989Dec5.195643.13592@sjsumcs.sjsu.edu >, 33014-18@sjsumcs.sjsu.edu (Eduardo Horvath) writes:
 > In article <62298@aerospace.AERO.ORG> abbott@aero.UUCP (Russell J. Abbott) writes:
 > >In article <32106@watmath.waterloo.edu> gjditchfield@watmsg.waterloo.edu (Glen Ditchfield) writes:
 > >>  ...   In practice, in C++, wouldn't it be simpler to pass a comparison
 > >>function as an argument to the sort() function?
 > >
 > >Can you really do that in C++?  What would the declarations look like?
 > >That would be even more flexible than the generic sort that I asked
 > >about originally.
 > >
 > 
 >     This is an old trick from C.  You pass a pointer to a function as
 > an argument to a sort function, and the sort function calls the comparison.

... non-C++ example deleted

 > 	b) Linkage problems occuring from compiling different object modules
 > 		with different function declarations.  This was a problem with
 > 		classic C, but in ANSI C or C++, correct prototyping and
 > 		recompiling all files where prototypes have been changed will
 > 		usually solve this problem.
 > 
 > I hope this helps.
 > 
 > 
 > Eduardo Horvath	|  San Jose State | 33014-18@sjsumcs.SJSU.EDU


As you mentioned, C++ has correct prototyping, and the qsort example
you have above relies on defeating the prototyping when passing the
comparison function as a parameter.  I agree with Glen that there is
no (type safe) way to do this in C++.

-- 
Gordon V. Cormack     CS Dept, University of Waterloo, Canada N2L 3G1
gvcormack@waterloo.EDU  gvcormack@uwaterloo.CA  gvcormac@water.BITNET