Re: Why the C programming language book was never updated past C89?

From	Ian Collins <ian-news@hotmail.com>
Newsgroups	comp.lang.c
Subject	Re: Why the C programming language book was never updated past C89?
Date	2015-02-06 10:54 +1300
Message-ID	<cji75fFq43fU2@mid.individual.net> (permalink)
References	(3 earlier) <mavqib$ah7$1@dont-email.me> <mavsi2$ibc$1@dont-email.me> <lnoap8kxf2.fsf@nuthaus.mib.org> <mb0gqs$e4i$1@dont-email.me> <lnh9v0kpf8.fsf@nuthaus.mib.org>

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Keith Thompson wrote:
> Bartc <bc@freeuk.com> writes:

>> Disadvantages of allowing declarations anywhere, and allowing the same
>> name to be used in different block scopes:
>>
>> * When encountering a variable name X, you have to scan backwards every
>> line from that point, to the start of the function, to look for the
>> nearest definition. [Instead of going straight to the start.]
>
> For relatively small functions, that shouldn't be too much of a problem.

If functions aren't relatively small, size is the problem!

>> * If you want to copy and paste fragments of code from one part of a
>> function to another, you'd better make sure you take include the
>> declarations of any variables! Otherwise there might be nasty surprises.

If you want to copy and paste fragments of code, extract them into 
functions.  Copy and paste is the programmer's equivalent of sneezing in 
a lift - it spreads bugs!

>> * If you want to document all the variables in a function, now it's a
>> much harder job because the declarations are disseminated through the
>> code with possibility of the same name used multiple times.
>
> I'm not sure documenting all the variables in a function would be
> useful.  I'd rather document sections of code.  In any case, unless your
> functions are unreasonably long, mixing declarations and statements
> isn't going to be a huge problem; the declarations still aren't that
> difficult to find.

Add to that variables declared where they are used are way more likely 
to be self documenting.  The context is the documentation.

>> * (More of technical objection but I'm uneasy with the idea of having a
>> name which is hard to pin down. If I want to talk about variable X in
>> function F, I now have to specify exactly which block of F it's defined
>> in, especially if there are several Xs; how do I do that?)
>
> By not defining multiple variables with the same name in the same
> function.

Also not making functions so complex that is is an issue.

>> Actually, given that people are always suggesting to keep functions
>> small, you have to wonder why it is necessary to declare a name right
>> next to it's first use instead of at the beginning of the function a
>> mere dozen lines away, if that.
>
> It's not *necessary*, but as I wrote upthread it can be handy to define
> a variable close to its first use, and to initialize it with a value
> that might depend on previous computations.

That last point is important, especially if you want the variable to be 
const.

-- 
Ian Collins

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