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Re: naming anonymous subroutines inner variables

by zwon (Abbot)
on Jun 22, 2016 at 21:04 UTC ( #1166308=note: print w/replies, xml ) Need Help??


in reply to naming anonymous subroutines inner variables

and $self->{ftest}() is the code that would execute it
That should be $self->{ftest}($self)

Update alternatively you can get rid of my $self = shift;

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Re^2: naming anonymous subroutines inner variables
by writch (Sexton) on Jun 22, 2016 at 21:46 UTC
    This is actually the controlling issue. $_ doesn't work in any case, but either the $k or the $closure method work with either $self supplied and shifted or ignored and not shifted

      either the $k or the $closure method work

      Be careful! Whilst the for my $name... works, it is dangerous:

      my @names = qw[ the quick brown fox ]; undef %h; for my $alias ( @names ){ $h{ $alias } = sub { print $alias; $alias = 'fred'; ####### Mysterious action at a distance +here }; }; pp \%h; { brown => sub { "???" }, fox => sub { "???" }, quick => sub { "???" }, the => sub { "???" }, } for my $key ( keys %h ) { $h{ $key }->(); };; the fox brown quick print @names;; fred fred fred fred

      With the for my $name ( ... ) method, the closures are and remain aliases to the source list in the for loop; which means that if you assign to the closure within the subroutine, you will cause spooky action at a distance to the content of that source.

      And perhaps worse, changes to the source of the for list, will remotely change the contents of the closures:

      [0]{} Perl> my @names = qw[ the quick brown fox ]; undef %h; for my $alias ( @names ){ $h{ $alias } = sub { print $alias; }; }; pp \%h; { brown => sub { "???" }, fox => sub { "???" }, quick => sub { "???" }, the => sub { "???" }, } $names[ 1 ] .= 'Mysterious changes'; ###### And again here! for my $key ( keys %h ) { $h{ $key }->(); };; the fox brown quickMysterious changes

      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority". I knew I was on the right track :)
      In the absence of evidence, opinion is indistinguishable from prejudice. Not understood.
        Be careful!

        Wise words. When I first posted this, I thought about adding some sort of note of caution about the aliasing, or just avoiding it altogether in the pseudo-code, but desisted because of concerns about minimizing changes to the OPed code and about brevity. The approaches here and here that entirely avoid aliasing are much better: an aliasing bug, if it manifests, can be a really nasty critter to deal with!


        Give a man a fish:  <%-{-{-{-<

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