Ref::Util • man page

Ref::Util (3)

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Standard preamble:
========================================================================

(The comments found at the beginning of the groff file "man3/Ref::Util.3pm".)

NAME

Ref::Util - Utility functions for checking references

VERSION

version 0.113

DESCRIPTION

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

    ref $foo eq 'ARRAY'

    # is now:

    is_arrayref($foo)

The difference:

*

Fast

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)

*

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:

*: "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.

Additionally, two implementations are available, depending on the perl version you have. For perls that supports Custom OPs, we actually add an

(which is faster), and for perls that do not, we include an implementation that just calls an

function - which is still faster than the Pure-Perl equivalent.

We might also introduce a Pure-Perl version of everything, allowing to install and load the faster implementation seamlessly if possible.

This will allow projects to use an optionally-Pure-Perl version.

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($ref)

Check for a reference to anything.

    is_ref([]);

is_scalarref($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".

is_arrayref($ref)

Check for an array reference.

    is_arrayref([]);

is_hashref($ref)

Check for a hash reference.

    is_hashref({});

is_coderef($ref)

Check for a code reference.

    is_coderef( sub {} );

is_regexpref($ref)

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

    is_regexpref( qr// );

is_globref($ref)

Check for a glob reference.

    is_globref( \*STDIN );

is_formatref($ref)

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()".

is_ioref($ref)

Check for an

reference.

    is_ioref( *STDOUT{IO} );

is_refref($ref)

Check for a reference to a reference.

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

is_plain_scalarref($ref)

Check for an unblessed scalar reference.

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

is_plain_ref($ref)

Check for an unblessed reference to anything.

    is_plain_ref([]);

is_plain_arrayref($ref)

Check for an unblessed array reference.

    is_plain_arrayref([]);

is_plain_hashref($ref)

Check for an unblessed hash reference.

    is_plain_hashref({});

is_plain_coderef($ref)

Check for an unblessed code reference.

    is_plain_coderef( sub {} );

is_plain_globref($ref)

Check for an unblessed glob reference.

    is_plain_globref( \*STDIN );

is_plain_formatref($ref)

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'} );

is_plain_refref($ref)

Check for an unblessed reference to a reference.

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

is_blessed_scalarref($ref)

Check for a blessed scalar reference.

    is_blessed_scalarref(bless \$value);

is_blessed_ref($ref)

Check for a blessed reference to anything.

    is_blessed_ref(bless [], $class);

is_blessed_arrayref($ref)

Check for a blessed array reference.

    is_blessed_arrayref(bless [], $class);

is_blessed_hashref($ref)

Check for a blessed hash reference.

    is_blessed_hashref(bless {}, $class);

is_blessed_coderef($ref)

Check for a blessed code reference.

    is_blessed_coderef( bless sub {}, $class );

is_blessed_globref($ref)

Check for a blessed glob reference.

    is_blessed_globref( bless \*STDIN, $class );

is_blessed_formatref($ref)

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 );

is_blessed_refref($ref)

Check for a blessed reference to a reference.

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

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>

COPYRIGHT AND LICENSE

This is free software, licensed under:

  The MIT (X11) License

Ref::Util • man page

Ref::Util • man page

Ref::Util (3)

Leading comments

NAME

VERSION

DESCRIPTION

EXPORT

SUBROUTINES

is_ref($ref)

is_scalarref($ref)

is_arrayref($ref)

is_hashref($ref)

is_coderef($ref)

is_regexpref($ref)

is_globref($ref)

is_formatref($ref)

is_ioref($ref)

is_refref($ref)

is_plain_scalarref($ref)

is_plain_ref($ref)

is_plain_arrayref($ref)

is_plain_hashref($ref)

is_plain_coderef($ref)

is_plain_globref($ref)

is_plain_formatref($ref)

is_plain_refref($ref)

is_blessed_scalarref($ref)

is_blessed_ref($ref)

is_blessed_arrayref($ref)

is_blessed_hashref($ref)

is_blessed_coderef($ref)

is_blessed_globref($ref)

is_blessed_formatref($ref)

is_blessed_refref($ref)

SEE ALSO

THANKS

AUTHORS

LICENSE

AUTHORS

COPYRIGHT AND LICENSE

Man Section

extra • Version

extra • Source

extra • Book