gaal,
I read the slides from your lightning talk. They were interesting. One thing that I might add (or otherwise comment on) is the suggestion that while() doesn't localize $_. While this is true, it's probably more accurate to state that <FH>; doesn't localize $_. Because the fact is that while() isn't itself acting on $_. The action is carried out by the diamond operator implicitly spilling its guts into $_. while() doesn't really have much to do with it, though we get in the habbit of thinking that it does since the while( <> ) construct is so common, and since foreach loops default to acting upon $_.
Also commenting on your slides (not having heard the lecture), foreach is the exception as you said, but this is because foreach works in an entirely different way than while(). With respect to foreach, it is the loop construct itself that acts upon $_, in a very special way. We even write it in a very special way (if we write it out longhand):
foreach $_ ( list )
...that's how foreach deparses with B::Deparse. Your slides mention that foreach is the exception. While it is an exception, it is not the only one. map also is a looping mechanism where $_ is localized. Consider the following code:
$_ = "Test string\n"; my @array = map { $_ = chr $_ } 32 .. 64; print $_; __OUTPUT__ Test string
As you can see, the use of $_ inside of map works a lot like the iterator of a foreach loop, in that it serves as an alias to the elements of the input list (ok, my example doesn't demonstrate this, but it's true), and in that it is localized (my snippet shows this to be the case).
Just a few observations and additional meditations... ;)
Dave
In reply to Re^2: Playing with non-localized $_ in nested loops.
by davido
in thread Playing with non-localized $_ in nested loops.
by davido
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