Re: C 99 compiler access

From: Arthur J. O'Dwyer (ajo_at_nospam.andrew.cmu.edu)
Date: 08/29/04 

Date: Sun, 29 Aug 2004 12:59:32 -0400 (EDT)

On Sun, 29 Aug 2004, Ben Pfaff wrote:
>
> "Malcolm" <malcolm@55bank.freeserve.co.uk> writes:
>> Instead we had a lot of feature of dubious use which require rewrites of the
>> compiler. For instance variables can now be declared anywhere, which seems
>> to be just a way of making code less organised and harder to read, [...]
>
> I disagree. Declaring a variable in mid-block is a valuable way
> to reduce the scope of that variable, giving the programmer less
> time to screw it up. Furthermore, a variable declared in
> mid-block can usually be initialized in the declaration, which
> means there's a bigger chance it can be marked `const', which in
> turn gives the programmer less to screw up.

   I would agree with you [Ben] if there were some intuitive mechanism
in C99 for /closing/ the scope of a variable with a minimum of clutter.
That is, a lot of the time I want to write the equivalent of:

     int foo, baz;
     process(foo, baz);
     { /* scope opens */
         int bar = 2*foo+1;
         process2(bar);
     } /* scope closes */
     process(baz, foo);

   The above code is valid C90 and C99, but it's ugly (IMHO) because
the braces and indentation don't actually represent any control
structure.
   C99 fixes /half/ of the problem by letting me write

     int foo, baz;
     process(foo, baz);
     int bar = 2*foo+1; /* scope opens */
     process2(bar);
     process(baz, foo);

but now, as I said, the problem is that there's no way to "close" the
scope of 'bar' where I intend. 'bar' can be destroyed (by the computer)
and forgotten about (by the reader) once we get to line 5; unfortunately,
there's no way to tell the reader that. And in a long function, the
mental clutter of so many "scope-unclosed" temporary variables can really
impede understanding. ("Okay, here he's defining 'bar'. And he uses it
on the next line... and nowhere else? That can't be right... grep grep...
okay, I guess that is right. Now where was I?")

   At least, that's what I find. YMMV.

-Arthur

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