Path: utzoo!attcan!utgpu!news-server.csri.toronto.edu!rutgers!usc!wuarchive!uunet!mtndew!friedl
From: friedl@mtndew.Tustin.CA.US (Steve Friedl)
Newsgroups: comp.lang.c
Subject: Re: Is this bad programming?
Keywords: #define array definition
Message-ID: <499@mtndew.Tustin.CA.US>
Date: 19 Aug 90 17:07:37 GMT
References: <1990Aug8.100614.1223@resam.dk> <1990Aug9.054556.22271@athena.mit.edu>
Organization: VSI*FAX Tech Ctr, Tustin, CA
Lines: 41

Steve Summit writes:
> [Others] worry about keeping error numbers in sync with an array of
> error message strings so that the array can be indexed by the
> array number.
> 
> Whenever I'm serious about making the connection between error
> numbers and messages explicit rather than implicit, I do so
> quite, er, explicitly:
> 
> 	#define	FILE_FOOTER_ERROR		1
> 	#define	DRAW_FOOTER_ERROR		2
> 
> 	struct errmess { int em_number; char *em_text; } errmesses[] =
>	{ FILE_FOOTER_ERROR,	"File footer error",
>	  DRAW_FOOTER_ERROR,	"Draw footer error",
>	  ... };

[ style compressed by me ]

I occasionally have to do this kind of thing for a case where I must
access the array repeatedly, and the search time is more than I care
to allow.  So, I define a table just as Steve does above, then define
an auxilliary table of pointers to these structs that I build at
runtime.  This way I can lay out the table in no particular order,
and the runtime sorter stuffs in all the relevant values (including
a pointer to a single static "dummy" value for holes in the array).

It does require a hit at runtime, but it means that I can do things
like an array of signal names without having to do a *horrible*
#ifdef dance that depends on my knowing which signal numbers have
which values.  I have seen people try to build these tables for
multiple machines, and in my opinion it is ridiculous to try to
do so.

     Steve

-- 
Stephen J. Friedl, KA8CMY / Software Consultant / Tustin, CA / 3B2-kind-of-guy
+1 714 544 6561  / friedl@mtndew.Tustin.CA.US  / {uunet,attmail}!mtndew!friedl

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