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Re^2: Reference assessment techniques and how they fail

by kyle (Abbot)
on Feb 17, 2008 at 17:18 UTC ( #668419=note: print w/ replies, xml ) Need Help??


in reply to Re: Reference assessment techniques and how they fail
in thread Reference assessment techniques and how they fail

Good point, but there's actually another problem I forgot to mention. In a &{}, undef is code.

use strict; use warnings; use Test::More 'tests' => 3; sub is_code { no warnings qw( void uninitialized ); return eval { defined &{$_[0]}; 1 }; } sub real_sub { die 'real sub called' } my $sub_ref = sub { die 'sub ref called' }; my $undef; ok( is_code( \&real_sub ), 'real sub ref is code' ); ok( is_code( $sub_ref ), 'lexical sub ref is code' ); ok( is_code( $undef ), 'undef is code' );

This isn't a big deal, I guess. We just have to change is_code to return defined $_[0] && eval { defined &{$_[0]}; 1 };. Still, I'd rather call something that figures out what it is than call it to figure out what it is.


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Re^3: Reference assessment techniques and how they fail
by shmem (Canon) on Feb 17, 2008 at 19:04 UTC
    Good point, but there's actually another problem I forgot to mention. In a &{}, undef is code.

    That's not true. Why is your eval always returning 1 unless it dies? With

    sub is_code { no warnings qw( void uninitialized ); return eval { defined &{$_[0]} }; }

    things look more reasonable. If undef were code, it'd be a serious bug.

    --shmem

    _($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                                  /\_¯/(q    /
    ----------------------------  \__(m.====·.(_("always off the crowd"))."·
    ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

      Ah, you're right. I was thinking of the wrong exception and wrote the wrong test.

      use Test::More 'tests' => 5; sub is_code { no warnings qw( void uninitialized ); return eval { defined &{$_[0]} }; } sub real_sub { die 'real sub called' } my $sub_ref = sub { die 'sub ref called' }; my $undef; ok( is_code( \&real_sub ), 'real sub ref is code' ); ok( is_code( $sub_ref ), 'lexical sub ref is code' ); ok( ! is_code( $undef ), 'undef is not code' ); ok( ! is_code( 'string' ), 'string is not code' ); ok( is_code( 'real_sub' ), 'string is code' );

      So you still need an extra check in is_code.

      sub is_code { no warnings qw( void uninitialized ); return '' ne ref $_[0] && eval { defined &{$_[0]} }; }

      That's fairly simple, but I think I still prefer the battery of ref, Scalar::Util::reftype, Scalar::Util::blessed and overload::Method.

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