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From: marks@cbnewsl.att.com (mark.e.smith)
Newsgroups: comp.lang.c
Subject: Re: Grouse: What's the point of enum?
Message-ID: <1991Apr22.033654.4354@cbnewsl.att.com>
Date: 22 Apr 91 03:36:54 GMT
References: <12236@dog.ee.lbl.gov> <41440@cup.portal.com> <678@taumet.com>
Organization: AT&T Bell Laboratories
Lines: 39

In article <678@taumet.com> steve@taumet.com (Stephen Clamage) writes:
>ts@cup.portal.com (Tim W Smith) writes:
>
>>Anyway, the real point is to allow lower case names for constants.  If
>>you try this in a header file...
>

I love it.  Score one for the anti-style guide side.

>
>Preprocessor defines have no scope.  They reach into the internals of
>structs and functions and can result in mystifying error messages and
>hard-to-find bugs.  The enumeration names are scoped, and can be made
>local to functions if desired, and can be locally overridden inside
>functions which don't know and don't want to know about a #define (or
>enum) buried inside some nested include file.

Yes.  The answer hints at the model, which is that an enum defines a type,
i.e. a set of values.  Defining types is a Good Thing.  Otherwise, there's
nothing in the program syntax which hints at the relationship among the values.

Compare for example the three styles:

#define APPLE 1
#define ORANGE 2

vs.

#define APPLE 1
#define ORANGE ( APPLE + 1 )

which is better, since at least we have some clue that an apple and an
orange are somehow related; vs.

enum { APPLE = 1, ORANGE } ;

which is explicit.

Mark Smith