yary not.com-at-gmail.com |Perl 6| wrote:
I was wondering why the perl5 example didn't work in p6- $_ is a
contextual variable,
so why doesn't the body of "odd" get its $_ value
from grep in something like this:
sub odd_a { $_ % 2}
If you make it a formally declared "sub", then you have to set up your
local $_ yourself. If you wrote it as a bare block, then using $_ in
that block would be enough to make it your parameter.
If you don't declare it, I'm not sure if you get a local one implicitly
or if it makes a closure from the lexical scope containing the sub.
Either way, it's not the dynamic scope.
sub odd_b { $*_ % 2}
Sayith S02, "Note that |$*_| will always see the |$_| in the current
scope, not the caller's scope"
That implies that it is declared for you whether you use or not.
sub odd_c { $CONTEXT::_ % 2 }
I'd prefer CALLER to CONTEXT, but in this case they should be the same.
say grep &odd_a, 0..6
(calls "say" 7 times with an uninitialized value. Same with &odd_b, &odd_c)
So the answer to "
why the perl5 example didn't work" is "more use of lexical scoping rules."
--John
