Ref::Util(3pm) User Contributed Perl Documentation Ref::Util(3pm)

Ref::Util - Utility functions for checking references

version 0.204

    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 };
    }

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:

  • "VSTRING"

    This is a "PVMG" ("normal" variable) with a flag set for VSTRINGs. Since this is not a reference, it is not supported.

  • "LVALUE"

    A variable that delegates to another scalar. Since this is not a reference, it is not supported.

  • "INVLIST"

    I couldn't find documentation for this type.

Support might be added, if a good reason arises.

•
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.

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';

Check for a reference to anything.

    is_ref([]);

Check for a scalar reference.

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

Note that, even though a reference is itself a type of scalar value, a reference to another reference is not treated as a scalar reference:

    !is_scalarref(\\1);

The rationale for this is two-fold. First, callers that want to decide how to handle inputs based on their reference type will usually want to treat a ref-ref and a scalar-ref differently. Secondly, this more closely matches the behavior of the "ref" built-in and of "reftype" in Scalar::Util, which report a ref-ref as "REF" rather than "SCALAR".

Check for an array reference.

    is_arrayref([]);

Check for a hash reference.

    is_hashref({});

Check for a code reference.

    is_coderef( sub {} );

Check for a regular expression (regex, regexp) reference.

    is_regexpref( qr// );

Check for a glob reference.

    is_globref( \*STDIN );

Check for a format reference.

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

This function is not available in Perl 5.6 and will trigger a "croak()".

Check for an IO reference.

    is_ioref( *STDOUT{IO} );

Check for a reference to a reference.

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

Check for an unblessed scalar reference.

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

Check for an unblessed reference to anything.

    is_plain_ref([]);

Check for an unblessed array reference.

    is_plain_arrayref([]);

Check for an unblessed hash reference.

    is_plain_hashref({});

Check for an unblessed code reference.

    is_plain_coderef( sub {} );

Check for an unblessed glob reference.

    is_plain_globref( \*STDIN );

Check for an unblessed format reference.

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

Check for an unblessed reference to a reference.

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

Check for a blessed scalar reference.

    is_blessed_scalarref(bless \$value);

Check for a blessed reference to anything.

    is_blessed_ref(bless [], $class);

Check for a blessed array reference.

    is_blessed_arrayref(bless [], $class);

Check for a blessed hash reference.

    is_blessed_hashref(bless {}, $class);

Check for a blessed code reference.

    is_blessed_coderef( bless sub {}, $class );

Check for a blessed glob reference.

    is_blessed_globref( bless \*STDIN, $class );

Check for a blessed format reference.

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

Check for a blessed reference to a reference.

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

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%)

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

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

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

This is free software, licensed under:

  The MIT (X11) License
2022-12-07 perl v5.36.0