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Re: SVN type concerns

From: Kevin Pilch-Bisson <kevin_at_pilch-bisson.net>
Date: 2001-02-23 14:27:49 CET

I'm +1 on keeping and using svn_boolean_t and TRUE and false, for all
the same reasons Greg points out below.

On Thu, Feb 22, 2001 at 09:00:07PM -0800, Greg Stein wrote:
> On Thu, Feb 22, 2001 at 01:34:18PM -0600, Karl Fogel wrote:
> >...
> > I definitely find that svn_boolean_t makes code more readable for me;
> > I think cmpilato and a few others feel the same way.
> This is because you see "int" and wonder about the domain of legal values.
> Can you use -3? How about 42?
> If you see svn_boolean_t or bool or boolean, you *know* the domain is
> comprised of 0 and 1. Anything else is "illegal".
> On the other side of the boolean wall, when you see a function used like
> this:
> call_some_func ("your mom", "your brother", "don't want to know", 1);
> What the hell does that 1 mean? What if I passed 7?
> If the last line said TRUE, then I know it is representing a boolean value.
> Sure, sure... "documentation saves all". Not when you're reading through
> pages of code. Relying on the doc to pull yourself out of this situation is
> a bit scary. Want an excellent example case? Consider the other day when Jim
> put -1 into the code. Sure, the doc *over in that file there* said what the
> hell it meant, but I wasn't reading that file. I just saw -1 and wondered
> WTF that meant. Using a symbol such as SVN_FS__UNUSED_REVNUM would have been
> immediately obvious.
> TRUE and FALSE play the same game: *local* documentation for the task at
> hand.
> svn_boolean_t is great for documenting the constraints of the particular
> lvalue. TRUE/FALSE are great for documenting how a particular value is going
> to be interpreted.
> Documentation *elsewhere* can be helpful, but should never be considered the
> sole source. Local doc is always an improvement.
> Note that the use of svn_boolean_t and svn_revnum_t are analogous. Local doc
> about a particular type: its meaning, its domain, where it can be passed
> around (e.g. you don't pass an svn_revnum_t to a func taking a long int:
> there is probably a mistake somewhere (possibly as mundane as a mistype on
> the func decl)). TRUE and SVN_INVALID_REVNUM are also analogous.
> Cheers,
> -g
> --
> Greg Stein, http://www.lyra.org/

Kevin Pilch-Bisson                    http://www.pilch-bisson.net
     "Historically speaking, the presences of wheels in Unix
     has never precluded their reinvention." - Larry Wall

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