NAME¶

Ref::Util - Utility functions for checking references

VERSION¶

version 0.203

SYNOPSIS¶

    use Ref::Util qw( is_plain_arrayref is_plain_hashref );
    if ( is_plain_arrayref( $something ) ) {
        print for @{ $something };
    } elsif ( is_plain_hashref( $something ) ) {
        print for sort values %{ $something };
    }

DESCRIPTION¶

Ref::Util introduces several functions to help identify references in a smarter (and usually faster) way. In short:

    # conventional approach             # with Ref::Util
    ref( $foo ) eq 'ARRAY'              is_plain_arrayref( $foo )
    use Scalar::Util qw( reftype );
    reftype( $foo ) eq 'ARRAY'          is_arrayref( $foo )

The difference:

• No comparison against a string constant

  When you call "ref", you stringify the reference and then compare it to some string constant (like "ARRAY" or "HASH"). Not just awkward, it's brittle since you can mispell the string.

  If you use Scalar::Util's "reftype", you still compare it as a string:

      if ( reftype($foo) eq 'ARRAY' ) { ... }
      

• Supports blessed variables

  Note: In future versions, the idea is to make the default functions use the plain variation, which means explicitly non-blessed references.

  If you want to explicitly check for blessed references, you should use the "is_blessed_*" functions. There will be an "is_any_*" variation which will act like the current main functions - not caring whether it's blessed or not.

  When calling "ref", you receive either the reference type (SCALAR, ARRAY, HASH, etc.) or the package it's blessed into.

  When calling "is_arrayref" (et. al.), you check the variable flags, so even if it's blessed, you know what type of variable is blessed.

      my $foo = bless {}, 'PKG';
      ref($foo) eq 'HASH'; # fails
      use Ref::Util 'is_hashref';
      my $foo = bless {}, 'PKG';
      is_hashref($foo); # works
      

  On the other hand, in some situations it might be better to specifically exclude blessed references. The rationale for that might be that merely because some object happens to be implemented using a hash doesn't mean it's necessarily correct to treat it as a hash. For these situations, you can use "is_plain_hashref" and friends, which have the same performance benefits as "is_hashref".

  There is also a family of functions with names like "is_blessed_hashref"; these return true for blessed object instances that are implemented using the relevant underlying type.

• Supports tied variables and magic

  Tied variables (used in Readonly, for example) are supported.

      use Ref::Util qw<is_plain_hashref>;
      use Readonly;
      Readonly::Scalar my $rh2 => { a => { b => 2 } };
      is_plain_hashref($rh2); # success
      

  Ref::Util added support for this in 0.100. Prior to this version the test would fail.

• Ignores overloading

  These functions ignore overloaded operators and simply check the variable type. Overloading will likely not ever be supported, since I deem it problematic and confusing.

  Overloading makes your variables opaque containers and hides away what they are and instead require you to figure out how to use them. This leads to code that has to test different abilities (in "eval", so it doesn't crash) and to interfaces that get around what a person thought you would do with a variable. This would have been alright, except there is no clear way of introspecting it.

• Ignores subtle types:

  The following types, provided by Scalar::Util's "reftype", are not supported:

•

Usually fast

When possible, Ref::Util uses Ref::Util::XS as its implementation. (If you don't have a C compiler available, it uses a pure Perl fallback that has all the other advantages of Ref::Util, but isn't as fast.)

In fact, Ref::Util::XS has two alternative implementations available internally, depending on the features supported by the version of Perl you're using. For Perls that supports custom OPs, we actually add an OP (which is faster); for other Perls, the implementation that simply calls an XS function (which is still faster than the pure-Perl equivalent).

See below for benchmark results.

EXPORT¶

Nothing is exported by default. You can ask for specific subroutines (described below) or ask for all subroutines at once:

    use Ref::Util qw<is_scalarref is_arrayref is_hashref ...>;
    # or
    use Ref::Util ':all';

SUBROUTINES¶

    is_ref([]);

    is_scalarref(\"hello");
    is_scalarref(\30);
    is_scalarref(\$value);

    !is_scalarref(\\1);

    is_arrayref([]);

    is_hashref({});

    is_coderef( sub {} );

    is_regexpref( qr// );

    is_globref( \*STDIN );

    # set up format in STDOUT
    format STDOUT =
    .
    # now we can test it
    is_formatref( *main::STDOUT{'FORMAT'} );

    is_ioref( *STDOUT{IO} );

    is_refref( \[] ); # reference to array reference

    is_plain_scalarref(\"hello");
    is_plain_scalarref(\30);
    is_plain_scalarref(\$value);

    is_plain_ref([]);

    is_plain_arrayref([]);

    is_plain_hashref({});

    is_plain_coderef( sub {} );

    is_plain_globref( \*STDIN );

    # set up format in STDOUT
    format STDOUT =
    .
    # now we can test it
    is_plain_formatref(bless *main::STDOUT{'FORMAT'} );

    is_plain_refref( \[] ); # reference to array reference

    is_blessed_scalarref(bless \$value);

    is_blessed_ref(bless [], $class);

    is_blessed_arrayref(bless [], $class);

    is_blessed_hashref(bless {}, $class);

    is_blessed_coderef( bless sub {}, $class );

    is_blessed_globref( bless \*STDIN, $class );

    # set up format for FH
    format FH =
    .
    # now we can test it
    is_blessed_formatref(bless *FH{'FORMAT'}, $class );

    is_blessed_refref( bless \[], $class ); # reference to array reference

BENCHMARKS¶

Here is a benchmark comparing similar checks.

    my $bench = Dumbbench->new(
        target_rel_precision => 0.005,
        initial_runs         => 20,
    );
    my $amount = 1e7;
    my $ref    = [];
    $bench->add_instances(
        Dumbbench::Instance::PerlSub->new(
            name => 'Ref::Util::is_plain_arrayref (CustomOP)',
            code => sub {
                Ref::Util::is_plain_arrayref($ref) for ( 1 .. $amount )
            },
        ),
        Dumbbench::Instance::PerlSub->new(
            name => 'ref(), reftype(), !blessed()',
            code => sub {
                ref $ref
                    && Scalar::Util::reftype($ref) eq 'ARRAY'
                    && !Scalar::Util::blessed($ref)
                    for ( 1 .. $amount );
            },
        ),
        Dumbbench::Instance::PerlSub->new(
            name => 'ref()',
            code => sub { ref($ref) eq 'ARRAY' for ( 1 .. $amount ) },
        ),
        Dumbbench::Instance::PerlSub->new(
            name => 'Data::Util::is_array_ref',
            code => sub { is_array_ref($ref) for ( 1 .. $amount ) },
        ),
    );

The results:

    ref():                                   5.335e+00 +/- 1.8e-02 (0.3%)
    ref(), reftype(), !blessed():            1.5545e+01 +/- 3.1e-02 (0.2%)
    Ref::Util::is_plain_arrayref (CustomOP): 2.7951e+00 +/- 6.2e-03 (0.2%)
    Data::Util::is_array_ref:                5.9074e+00 +/- 7.5e-03 (0.1%)

(Rounded run time per iteration)

A benchmark against Data::Util:

    Ref::Util::is_plain_arrayref: 3.47157e-01 +/- 6.8e-05 (0.0%)
    Data::Util::is_array_ref:     6.7562e-01 +/- 7.5e-04 (0.1%)

SEE ALSO¶

• Params::Classify
• Scalar::Util
• Data::Util

THANKS¶

The following people have been invaluable in their feedback and support.

• Yves Orton
• Steffen Müller
• Jarkko Hietaniemi
• Mattia Barbon
• Zefram
• Tony Cook
• Sergey Aleynikov

AUTHORS¶

• Aaron Crane
• Vikentiy Fesunov
• Sawyer X
• Gonzalo Diethelm
• p5pclub

LICENSE¶

This software is made available under the MIT Licence as stated in the accompanying LICENSE file.

AUTHORS¶

• Sawyer X <xsawyerx@cpan.org>
• Aaron Crane <arc@cpan.org>
• Vikenty Fesunov <vyf@cpan.org>
• Gonzalo Diethelm <gonzus@cpan.org>
• Karen Etheridge <ether@cpan.org>

COPYRIGHT AND LICENSE¶

This software is Copyright (c) 2017 by Sawyer X.

This is free software, licensed under:

  The MIT (X11) License