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# This program is free software; you can redistribute it and/or
# modify it under the same terms as Perl itself.
#
# Maintained since 2013 by Paul Evans <leonerd@leonerd.org.uk>

package Scalar::Util;

use strict;
use warnings;
require Exporter;

our @ISA       = qw(Exporter);
our @EXPORT_OK = qw(
  blessed refaddr reftype weaken unweaken isweak

  dualvar isdual isvstring looks_like_number openhandle readonly set_prototype
  tainted
);
our $VERSION    = "1.56";
$VERSION =~ tr/_//d;

require List::Util; # List::Util loads the XS
List::Util->VERSION( $VERSION ); # Ensure we got the right XS version (RT#100863)

our @EXPORT_FAIL;

unless (defined &weaken) {
  push @EXPORT_FAIL, qw(weaken);
}
unless (defined &isweak) {
  push @EXPORT_FAIL, qw(isweak isvstring);
}
unless (defined &isvstring) {
  push @EXPORT_FAIL, qw(isvstring);
}

sub export_fail {
  if (grep { /^(?:weaken|isweak)$/ } @_ ) {
    require Carp;
    Carp::croak("Weak references are not implemented in the version of perl");
  }

  if (grep { /^isvstring$/ } @_ ) {
    require Carp;
    Carp::croak("Vstrings are not implemented in the version of perl");
  }

  @_;
}

# set_prototype has been moved to Sub::Util with a different interface
sub set_prototype(&$)
{
  my ( $code, $proto ) = @_;
  return Sub::Util::set_prototype( $proto, $code );
}

1;

__END__

=head1 NAME

Scalar::Util - A selection of general-utility scalar subroutines

=head1 SYNOPSIS

    use Scalar::Util qw(blessed dualvar isdual readonly refaddr reftype
                        tainted weaken isweak isvstring looks_like_number
                        set_prototype);
                        # and other useful utils appearing below

=head1 DESCRIPTION

C<Scalar::Util> contains a selection of subroutines that people have expressed
would be nice to have in the perl core, but the usage would not really be high
enough to warrant the use of a keyword, and the size would be so small that 
being individual extensions would be wasteful.

By default C<Scalar::Util> does not export any subroutines.

=cut

=head1 FUNCTIONS FOR REFERENCES

The following functions all perform some useful activity on reference values.

=head2 blessed

    my $pkg = blessed( $ref );

If C<$ref> is a blessed reference, the name of the package that it is blessed
into is returned. Otherwise C<undef> is returned.

    $scalar = "foo";
    $class  = blessed $scalar;           # undef

    $ref    = [];
    $class  = blessed $ref;              # undef

    $obj    = bless [], "Foo";
    $class  = blessed $obj;              # "Foo"

Take care when using this function simply as a truth test (such as in
C<if(blessed $ref)...>) because the package name C<"0"> is defined yet false.

=head2 refaddr

    my $addr = refaddr( $ref );

If C<$ref> is reference, the internal memory address of the referenced value is
returned as a plain integer. Otherwise C<undef> is returned.

    $addr = refaddr "string";           # undef
    $addr = refaddr \$var;              # eg 12345678
    $addr = refaddr [];                 # eg 23456784

    $obj  = bless {}, "Foo";
    $addr = refaddr $obj;               # eg 88123488

=head2 reftype

    my $type = reftype( $ref );

If C<$ref> is a reference, the basic Perl type of the variable referenced is
returned as a plain string (such as C<ARRAY> or C<HASH>). Otherwise C<undef>
is returned.

    $type = reftype "string";           # undef
    $type = reftype \$var;              # SCALAR
    $type = reftype [];                 # ARRAY

    $obj  = bless {}, "Foo";
    $type = reftype $obj;               # HASH

Note that for internal reasons, all precompiled regexps (C<qr/.../>) are
blessed references; thus C<ref()> returns the package name string C<"Regexp">
on these but C<reftype()> will return the underlying C structure type of
C<"REGEXP"> in all capitals.

=head2 weaken

    weaken( $ref );

The lvalue C<$ref> will be turned into a weak reference. This means that