Re: What would you like in Ada202X?

[Mart van de Wege <mvdwege@mail.com>]

Adam Beneschan <adam@irvine.com> writes:

> On Wednesday, April 25, 2012 1:12:28 PM UTC-7,
> okel...@users.sourceforge.net wrote:
>> On Wednesday, April 25, 2012 9:15:13 PM UTC+2, Adam Beneschan wrote:
>> >  And why would having a "continue" statement be better than the
>> > workaround?
>>  Conciseness, plus avoidance of gratuitous "goto" (banned by various
>> coding guidelines)
>
> This is the sort of thing that makes me want to cry.  There's a reason
> "goto" is banned from some coding guidelines, and it's not because one
> day Dijkstra came down from a mountain with a slab that said "Thou
> shalt not use goto".  It's banned because in most cases, using it
> negatively impacts readability and (as Jeff said) there's almost
> always a better way.  I've tried to argue here that using "continue"
> is worse for readability than using a "goto" in this case--so if I'm
> right, it would make no sense to have coding guidelines that disallow
> "goto" and allow "continue".  Of course, if you're able to argue that
> the "continue" is more readable in this case, please do so.  But I
> suspect that's not possible if ...
>
Hmm.

I like the Perl use of 'next' and 'last' to influence looping.

Especially when looping over a list of values, it is nice to test for
values you don't want to process at the start of the loop, and
immediately go to the next iteration.

The canonical example is processing a file with comment lines starting
with '#':

while (<$file>) {
      next if /^#/; # skip comment lines
      [...Do stuff with line ...]
}

Now, this is a lot clearer, and IMO a lot more elegant, than putting a
label on the end of the loop and use 'goto label'. 

Although it *is* considered good practice to put your 'next' statements
at the top of the loop to make clear on what conditions the main body
will be skipped. 'next' statements littered throughout the body of the
loop are frowned upon.

Mart

-- 
"We will need a longer wall when the revolution comes."
    --- AJS, quoting an uncertain source.