Utility functions for checking references

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

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