NAME
Ref::Util - Utility functions for checking references
VERSION
0.011
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
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.
* 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 not supported, as
they are not references, but regular variables with added magic.
Consider the following:
use Data::Printer;
use Readonly;
Readonly::Scalar my $rh2 => { a => { b => 2 } };
p $rh2->{a};
# result:
# "HASH(0x187dcc8)"
This should print a hashref structure with key b and value 2, but it
doesn't. It prints a string. It should have retrieved the values but
caused stringification instead.
The problem here is that "$rh2->{a}" is not a hashref, but a "PVLV"
with magic, so "is_hashref" will correctly not detect 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
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_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" builtin 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($ref)
Check for an IO reference.
is_ioref( *STDOUT{IO} );
is_refref($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
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
* Aaron Crane