NAME

Ref::Util - Utility functions for checking references

VERSION

0.006

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

  The benchmark:

      my $bench = Dumbbench->new(
          target_rel_precision => 0.005,
          initial_runs         => 20,
      );
  
      my $ref = [];
      $bench->add_instances(
          Dumbbench::Instance::PerlSub->new(
              name => 'XS',
              code => sub { Ref::Util::is_arrayref($ref) for(1..1e7) },
          ),
  
          Dumbbench::Instance::PerlSub->new(
              name => 'reftype',
              code => sub { reftype($ref) eq 'ARRAY' for(1..1e7) },
          ),
  
          Dumbbench::Instance::PerlSub->new(
              name => 'PP',
              code => sub { ref($ref) eq 'ARRAY' for(1..1e7) },
          ),
      );

  The results:

      XS:      Ran 27 iterations (6 outliers).
      XS:      Rounded run time per iteration: 3.0093e-01 +/- 4.4e-04 (0.1%)
  
      reftype: Ran 25 iterations (5 outliers).
      reftype: Rounded run time per iteration: 9.173e-01 +/- 1.2e-03 (0.1%)
  
      PP:      Ran 26 iterations (6 outliers).
      PP:      Rounded run time per iteration: 6.1437e-01 +/- 3.4e-04 (0.1%)

• 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

  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

• 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. Ugh. Double Ugh. For this reason they are not supported.

  This is also not duck-typing, as at least one person suggested. Duck typing provides a method that *works* and has different implementations. The difference is that here we have different methods (stringification, array dereferencing, hash dereferencing, callbacks, greater-than comparsion, etc.) which have to be tested each individually. This is the opposite of duck-typing. Also, in duck-typing you can introspect to know what is available, and overloading does not lend to that.

  Overloading is cool, but terribly horrible. 'Nuff said.

• Readonly, tied variables, and magic

  Tied variables (used in Readonly, for example) are currently not supported, because they work similar to overloading by hiding away the implementation from the variable.

  Consider the following:

      use Data::Printer;
      Readonly::Scalar my $rh2 => { a => { b => 2 } };
      p $rh2->{a};
  
      # result:
      # "HASH(0x187dcc8)"

  This should print a hashref structure with key b and value 2, but it doesn't. It prints a string. It should have retrieved the values but caused stringification instead.

  Support for magic is still undetermined and being discussed. If you're interested in this, please join the conversation on Github.

• 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 perl that supports Custom OPs, we actually add an OP (which is faster), and for perls that do not, we include an implementation that just calls an XS function - which is still faster than the Pure-Perl equivalent.

We might also introduce a Pure-Perl version of everything, allowing to install this module where a compiler is not available, making the XS parts optional.

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_scalarref($ref)

Check for a scalar reference.

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

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 IO reference.

    is_ioref( *STDOUT{IO} );

is_refref($ref)

Check for a reference to a reference.

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

SEE ALSO

• Params::Classify

• Scalar::Util

THANKS

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

• Yves Orton

• Steffen Müller

• Jarkko Hietaniemi

• Mattia Barbon

AUTHORS

• Vikentiy Fesunov

• Sawyer X

• Gonzalo Diethelm

• p5pclub

cpanm Ref::Util

perl -MCPAN -e shell
install Ref::Util