On Wed, Aug 14, 2013 at 6:09 PM, Alexey Mishustin <shum...@shumkar.ru>wrote:
> 2013/8/15 Uri Guttman <u...@stemsystems.com>:
> > On 08/14/2013 04:22 PM, Jim Gibson wrote:
> >>
> >>
> >> On Aug 14, 2013, at 12:30 PM, Alexey Mishustin wrote:
> >>
> >>> Testing a value and assigning it - I have never done this at the same
> >>> time...
> >>
> >>
> >>
> >> Doing both in while statements is very common:
> >>
> >> while( my $line = <$fh> ) {
> >> ...
> >> }
> >>
> >> Try to write that loop with two separate statements, one an
> >> assignment
> >
> > and the other an if statement, and you may see the advantage of the
> > currently-allowed syntax.
> >>
> >>
> >> The general policy is that assignment statements return a value that
> >
> > may be further used or tested.
> >>
> >>
> >
> > i have a common idiom when dealing with a value in a hash:
> >
> > if( my $foo = $ref->{foo} ) {
> >
> > do stuff with $foo
> > }
> >
>
> OK, you have got me convinced. It's useful.
>
> I'm sorry only that there is no built-in option with which one could
> enable/disable easily assignments inside `if'. (E.g., like re 'eval'/
> no re 'eval'). It would "provide choices"...
>
>
It might not be too hard to implement that, actually. What follows is NOT a
topic for the beginners list, but feel free to nag perl5-porters about it
if you want to learn about the internals :D You "just" need to detect if
there's a LOGOP where op_type is OP_COND_EXPR and the condition is one of
the assign ops.
There's also room to improve this in the core itself -- I don't see why
this warns for
if ( $foo = 2 ) { ... }
but not for
if ( $foo = constant ) { ... }
Might be worth filing a bug there!
