Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question: 

my $foo = \&sin;
print $foo->(0.5), "\n";

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gives me a Undefined subroutine &main::sin called at - line 2. What am I doing wrong?

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Re: trouble taking reference of function
by samtregar (Abbot) on Mar 03, 2009 at 21:22 UTC
    Perl's builtins aren't generally made available as subs you can take a reference to. This works though: 

      my $foo = sub { sin(@_) };
  print $foo->(0.5), "\n";

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    -sam

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      Beware of prototypes when dealing with functions and named operators. 
      $ perl -wle'print sin(0.5) == sub { sin(@_)    }->(0.5) ?1:0'
0

$ perl -wle'print sin(0.5) == sub { sin($_[0]) }->(0.5) ?1:0'
1

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      Update: Added code.

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[d/l]

        Huh? Why does that happen?

        And you didn't even know bears could type.

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Re: trouble taking reference of function
by ikegami (Patriarch) on Mar 03, 2009 at 21:23 UTC

    sin is actually an operator, not a function. You can wrap it in a sub. 

    my $foo = sub { sin($_[0]) };

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Re: trouble taking reference of function
by Fletch (Bishop) on Mar 03, 2009 at 22:05 UTC

    TMTOWTDI . . . 

    use strict;
use POSIX qw( sin );

my $s = \&sin;

print $s->( 0.5 ), "\n";

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    (Not necessarily a good way, but . . . :)

    The cake is a lie.
    The cake is a lie.
    The cake is a lie.

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