kens@tekred.TEK.COM (Ken Spencer) (06/20/88)
I have just started using c++, I'd like to here what people think of "Friends considered harmful", and also "Static members considered harmful"(not const static members). I have heard of some people trying to go through an entire project without using any friend constructs because of the potential "spagetti code" syndrome. Is friend generally used as a hack to get around some problems with C++? How about static members, is this really a limited scope global object? -- Ken Spencer,Tekronix Inc. CNA Engineering Redmond, OR kens@speed.CNA.TEK.COM
tjt@ati.tis.llnl.gov (Tim Tessin) (06/21/88)
In article <2668@tekred.TEK.COM> kens@tekred.TEK.COM (Ken Spencer) writes: > I have just started using c++, I'd like to here what people > think of "Friends considered harmful", and also "Static members > considered harmful"(not const static members). > Is friend generally used as a hack to get around some > problems with C++? How about static members, is this really a > limited scope global object? > Ken Spencer,Tekronix Inc. Friends (of a class, not friend operators) are useful in allowing very limited and specific access beyond what public, private and protected allow. This shows up in a module where you would have several classes which intercommunicate and some are not useful outside of the module. Example is class Dlist which implements a doubly linked list. Class Dlink which is the actual implementation of the fwd and bkwd pointers is mostly private and allows access by friend Dlist and friend Dlist_Iterator. Dlink should not be allowed to be used by others just because it was defined in the same module with Dlist and Dlist_Iterator which are the "public" ways to fiddle with doubly linked lists. Static members are "shared storage" for all instances of a given class. They are not limited scope from the viewpoint of the class, they obey the same scoping rules as any "normal" member (public, private, etc). Static members are critical for doing things like window classes which need to init curses to get started. A static counter (nwin) can count all windows currently in existance and take care of cleanup when the last window goes away. Also, I have several static members in my base class for "Object" which does all kinds of accounting for "Objects". When my program terminates, I can tell how many objects were created, destroyed, etc. and tell if I have forgot to clean up properly. This has uncovered several bugs which I would never have found otherwise, especially when using reference counts for objects on lists and determining when to delete the object based on reference counts. Plug for C++: This would be next to impossible to get right in straight C. (It can be done, but who wants to take on the administrative headache in the main line code!) Tim Tessin - Lawrence Livermore National Laboratory PHONE: (415) 423-4560 ARPA: tjt@tis.llnl.gov UUCP: {ames,ihnp4,lll-crg,lll-lcc,mordor}!lll-tis!tjt
raila@uiucdcsm.cs.uiuc.edu (06/22/88)
I have used C++ for a couple small projects ( < 1K LOC).
The only times that I remember having used friends was to compensate for
a poor design job. It was much easier than restructuring classes, but
the "spaghetti code syndrome" was noticeable.
David K. Raila
University of Illinois
Dept. of Computer Science
1304 W. Springfield
Urbana, Il. 61801
UUCP: { ihnp4, pur-ee, convex }!uiucdcs!raila
ARPA: raila@a.cs.uiuc.edu