Re: private recursive subroutines

You can get around that by simply declaring $func as an undefined lexical and then re-defining it as a subroutine. Since the recursive call doesn't get executed until the sub is called for the first time, by that time, $func will contain the code reference. For example,

my $fac;

$fac = sub { 
    my ( $n ) = @_;
    return 1 if $n == 1;
    return $n * $fac->( $n - 1 );
};

print $fac->( 5 );
[download]

_{Yes, I know factorials are a bad example for recursion; it's just the first thing that came to mind. :)}

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Re^2: private recursive subroutines by blokhead (Monsignor) on May 10, 2007 at 16:36 UTC
This approach introduces a cyclic reference with $fac. `use Devel::Cycle; my $fac; $fac = sub { my ( $n ) = @_; return 1 if $n == 1; return $n * $fac->( $n - 1 ); }; find_cycle($fac); __END__ Cycle (1): $A variable $fac => \&A` [download] blokhead	[reply] [d/l]
Re^3: private recursive subroutines by Sixtease (Friar) on May 10, 2007 at 21:10 UTC
I can't say I understand much how the cycle gets introduced. Anyway, does `undef $fac` after the usage solve it?	[reply] [d/l]
Re^2: private recursive subroutines by Sixtease (Friar) on May 10, 2007 at 15:58 UTC
Wow this is cool and so much better than my solution! Thanks, I'll use it right away.	[reply]
Re^2: private recursive subroutines by naikonta (Curate) on May 10, 2007 at 15:51 UTC
The F is probably the most popular, followed by fibonacci. Both are mostly demonstrated at the normal sub level. There should be some specific merit(s) to have this recursive closure. But I will keep this in mind, though, and perhaps use it someday. Open source softwares? Share and enjoy. Make profit from them if you can. Yet, share and enjoy!	[reply]


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