Re^3: Why callbacks?


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Re^3: Why callbacks?

by Joost (Canon)

on Mar 30, 2007 at 17:32 UTC ( [id://607539]=note: print w/replies, xml )

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in reply to Re^2: Why callbacks?
in thread Why callbacks?

Named subroutines never go out of scope; they're global - bound to a package just like global variables.

Anonymous subrefs can go out of scope, just like any other variable, but, just like any other variable, you can pass them around:

sub call {
  my ($arg1,$arg2) = @_;
  my $callback = sub {
    my ($arg3) = @_;
    return $arg1 + $arg2 + $arg3;
  };
  call_func_needing_callback($callback);
}

# or even

sub call {
  my ($arg1,$arg2) = @_;
  call_func_needing_callback( sub {
    my ($arg3) = @_;
    return $arg1 + $arg2 + $arg3;
  });
}
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Also note that there are scoping issues with defining named closures within other subroutines (this probably has to do with named subroutines being global), while unnamed subroutines/closures will work as real lexical closures.

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