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package Scalar::Classify; |
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# doom@kzsu.stanford.edu |
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# 30 Jun 2015 |
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=head1 NAME |
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Scalar::Classify - get type and class information for scalars |
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=head1 SYNOPSIS |
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use Scalar::Classify qw( classify classify_pair ); |
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# determine the type (e.g. HASH for a hashref) and the object class (if any) |
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my ( $type, $class ) = classify( $some_scalar ); |
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# warn if two args differ, supply default if one is undef |
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my $default_value = |
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classify_pair( $arg1, $arg2 ); |
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# Also get type and class; error out if two args differ |
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my ( $default_value, $type, $class ) = |
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classify_pair( $arg1, $arg2, { mismatch_policy => 'error' }); |
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# If a given ref was undef, replace it with a default value |
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classify_pair( $arg1, $arg2, { also_qualify => 1 }); |
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=head1 DESCRIPTION |
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Scalar::Classify provides a routine named "classify" that can be used |
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to examine a given argument to determine it's type and class (if any). |
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Here "type" means either the return from reftype (, or if it's a scalar, |
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a code indicating whether it's a string or a number, and "class" |
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it the object class, the way a reference has been blessed. |
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This module also provides the routine "classify_pair", which |
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looks at a pair of variables intended to be of the same type, and |
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if at least one of them is defined, uses that to get an |
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appropriate default value for that type. |
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=head2 MOTIVATION |
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Perl contains a built-in "ref" function, and has some useful |
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routines in the standard Scalar::Util library ('ref', |
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'looks_like_number') which can be used to examine the type of an |
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argument. The classify routine provided here internally uses all |
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three of these, returning a two-values that describe the kind of |
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thing you're examining. |
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The immediate goal was to provide support routines for the |
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L project. |
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=head2 EXPORT |
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None by default. Optionally: |
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=over |
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=cut |
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use 5.008; |
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use strict; |
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use warnings; |
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my $DEBUG = 1; |
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use Carp; |
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use Data::Dumper; |
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use Scalar::Util qw( reftype looks_like_number ); |
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our (@ISA, @EXPORT_OK, %EXPORT_TAGS, @EXPORT); |
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BEGIN { |
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require Exporter; |
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@ISA = qw(Exporter); |
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%EXPORT_TAGS = ( 'all' => [ |
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qw( |
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classify |
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classify_pair |
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) ] ); |
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# The above allows use Scalar::Classify ':all'; |
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@EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } ); |
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@EXPORT = qw( ); |
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} |
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our $VERSION = '0.02'; |
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=item classify |
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Example usage: |
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my ( $type, $class ) = classify( $some_var ); |
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Returns two pieces of information, the underlying "type", and the |
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"class" (if this is a reference blessed into a class). |
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The type is most often (but not limited to) one of the following: |
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ARRAY |
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HASH |
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:NUMBER: |
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:STRING: |
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Other possibilities are the other potential returns from L[: ] |
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CODE |
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GLOB |
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LVALUE |
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FORMAT |
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IO |
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VSTRING |
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Regexp |
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Internally, this uses the built-in function L[ and the library ] |
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functions L and L (from L). |
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The type is the return from "reftype" (e.g "ARRAY", "HASH") |
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except that in the case of a simple scalar the type is a code to |
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indicate whether it seems to be a number (":NUMBER:") or a string |
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(":STRING:"). |
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Note: if the argument is undefined, the returned type is undef. |
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=cut |
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sub classify { |
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my $arg = shift; |
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# initialize $type to ref() |
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my $type = ref( $arg ); # '' if undef |
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my $basetype = reftype( $arg ) ; # undef if undef |
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my $class; # default undef |
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# it's a blessed ref when ref() not same as reftype() |
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if ( defined( $basetype ) && $type ne $basetype ) { |
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$class = $type; |
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$type = $basetype; |
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} |
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if( defined $arg ) { |
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# if not reference, we're handling a scalar |
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if ( not( defined( $basetype ) ) ) { |
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if( looks_like_number( $arg ) ) { |
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$type = ':NUMBER:'; |
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} else { |
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$type = ':STRING:'; |
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} |
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} |
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} else { |
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$type = undef; # more perlish than an empty string |
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} |
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my @meta = ( $type, $class ); |
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return wantarray ? @meta : \@meta; |
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} |
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=item classify_pair |
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Examines a pair of arguments that are intended to be processed in |
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parallel and are expected to be of the same type: |
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If they're both defined, it checks that their types match. |
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If at least one is defined, it generates a default of the |
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same type by using the L method. If both are |
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undef, this default is also undef. |
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In scalar context, it returns just the default value. |
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In list context, it returns the default plus the type and |
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the class (if it's a blessed reference). |
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An options hashref is accepted as a third argument, with |
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allowed options: |
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o mismatch_policy |
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If argument types mismatch, the behavior is determined by |
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the mismatch_policy option, defaulting to 'warn'. |
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The other allowed values are 'error' or 'silent'. |
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o also_qualify |
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If the "also_qualify" option is set to a true value, then |
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the given arguments may be modified in place: if one is |
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undef, it will be assigned the determined default. |
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Examples: |
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my $default_value = |
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classify_pair( $arg1, $arg2, { mismatch_policy => 'error' }); |
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191
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my ( $default_value, $type, $class ) = |
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classify_pair( $arg1, $arg2, { mismatch_policy => 'error' }); |
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194
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classify_pair( $arg1, $arg2, { also_qualify => 1 }); |
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Note the slightly unusual polymorphic behavior: in scalar |
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context returns *just* the default_value, in list context, |
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returns up to three values, the default, the type and the class. |
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200
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201
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=cut |
202
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203
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sub classify_pair { |
204
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1
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my $subname = ( caller(0) )[3]; |
205
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my $opt = $_[2]; |
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207
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my $policy = $opt->{ mismatch_policy } || 'warn'; |
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my $do_qualify = $opt->{ also_qualify } || 0; |
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210
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23
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my $meta1 = classify( $_[0] ); |
211
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14
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24
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my $meta2 = classify( $_[1] ); |
212
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213
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# handle mismatched types |
214
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29
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if ( $policy ne 'silent' ) { |
215
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no warnings 'uninitialized'; |
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597
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43
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if ( defined( $_[0] ) && defined( $_[1] ) ) { |
217
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7
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unless( $meta1->[0] eq $meta2->[0] ) { |
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35
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croak "mismatched types: $meta1->[0] and $meta2->[0]" if $policy eq 'error'; |
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0
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carp "mismatched types: $meta1->[0] and $meta2->[0]" if $policy eq 'warn'; |
220
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} |
221
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1
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50
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15
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unless( $meta1->[1] eq $meta2->[1] ) { |
222
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1
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50
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11
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croak "mismatched classes: $meta1->[1] and $meta2->[1]" if $policy eq 'error'; |
223
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0
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0
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0
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carp "mismatched classes: $meta1->[1] and $meta2->[1]" if $policy eq 'warn'; |
224
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} |
225
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} |
226
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} |
227
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228
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10
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11
|
my ( $defval, $class, $type ); |
229
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4
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4
|
|
92
|
{ no warnings 'uninitialized'; |
|
4
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5
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4
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|
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308
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10
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|
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|
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26
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|
230
|
10
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66
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33
|
$type = $meta1->[0] || $meta2->[0]; |
231
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} |
232
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10
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50
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|
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|
32
|
unless( defined( $type ) ) { |
233
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0
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0
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|
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|
0
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return wantarray ? ( undef, undef, undef ) : undef; |
234
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} |
235
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236
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10
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100
|
|
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|
22
|
if ( $type eq ':NUMBER:' ) { |
|
|
100
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|
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|
237
|
3
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|
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3
|
$defval = 0; |
238
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|
} elsif ( $type eq ':STRING:' ) { |
239
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1
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3
|
$defval = ''; |
240
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} else { |
241
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4
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4
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|
19
|
{ no warnings 'uninitialized'; |
|
4
|
|
|
|
|
4
|
|
|
4
|
|
|
|
|
692
|
|
|
6
|
|
|
|
|
5
|
|
242
|
6
|
|
66
|
|
|
16
|
$class = $meta1->[1] || $meta2->[1]; |
243
|
|
|
|
|
|
|
} |
244
|
6
|
100
|
|
|
|
19
|
if ( $type eq 'ARRAY' ) { |
|
|
50
|
|
|
|
|
|
|
|
0
|
|
|
|
|
|
245
|
2
|
|
|
|
|
3
|
$defval = []; |
246
|
|
|
|
|
|
|
} elsif ( $type eq 'HASH' ) { |
247
|
4
|
|
|
|
|
6
|
$defval = {}; |
248
|
|
|
|
|
|
|
} elsif ( $type eq 'SCALAR' ) { |
249
|
0
|
|
|
|
|
0
|
my $var; |
250
|
0
|
|
|
|
|
0
|
$defval = \$var; |
251
|
|
|
|
|
|
|
} else { # handle the useless cases: warn and get out of here |
252
|
0
|
|
|
|
|
0
|
carp "$subname can't do anything useful with ref type $type"; |
253
|
|
|
|
|
|
|
} |
254
|
|
|
|
|
|
|
} |
255
|
|
|
|
|
|
|
|
256
|
10
|
100
|
66
|
|
|
43
|
if( defined( $defval ) && defined( $class ) ) { |
257
|
2
|
|
|
|
|
3
|
bless( $defval, $class ); |
258
|
|
|
|
|
|
|
} |
259
|
|
|
|
|
|
|
|
260
|
10
|
100
|
|
|
|
17
|
if( $do_qualify ) { |
261
|
1
|
50
|
|
|
|
3
|
$_[0] = $defval unless defined( $_[0] ); |
262
|
1
|
50
|
|
|
|
3
|
$_[1] = $defval unless defined( $_[1] ); |
263
|
|
|
|
|
|
|
} |
264
|
|
|
|
|
|
|
|
265
|
10
|
100
|
|
|
|
52
|
return wantarray ? ( $defval, $type, $class ) : $defval; |
266
|
|
|
|
|
|
|
} |
267
|
|
|
|
|
|
|
|
268
|
|
|
|
|
|
|
|
269
|
|
|
|
|
|
|
1; |
270
|
|
|
|
|
|
|
|
271
|
|
|
|
|
|
|
=back |
272
|
|
|
|
|
|
|
|
273
|
|
|
|
|
|
|
=head1 SEE ALSO |
274
|
|
|
|
|
|
|
|
275
|
|
|
|
|
|
|
L |
276
|
|
|
|
|
|
|
|
277
|
|
|
|
|
|
|
This covers the argument checking case, where you want to verify |
278
|
|
|
|
|
|
|
that something of the correct type was passed. The perl5-porters |
279
|
|
|
|
|
|
|
are interested in adding core support for this module: it's fast |
280
|
|
|
|
|
|
|
and likely to get faster. |
281
|
|
|
|
|
|
|
|
282
|
|
|
|
|
|
|
=head1 AUTHOR |
283
|
|
|
|
|
|
|
|
284
|
|
|
|
|
|
|
Joseph Brenner, Edoom@kzsu.stanford.eduE |
285
|
|
|
|
|
|
|
|
286
|
|
|
|
|
|
|
=head1 COPYRIGHT AND LICENSE |
287
|
|
|
|
|
|
|
|
288
|
|
|
|
|
|
|
Copyright (C) 2016 by Joseph Brenner |
289
|
|
|
|
|
|
|
|
290
|
|
|
|
|
|
|
This library is free software; you can redistribute it and/or modify |
291
|
|
|
|
|
|
|
it under the same terms as Perl itself. |
292
|
|
|
|
|
|
|
|
293
|
|
|
|
|
|
|
See http://dev.perl.org/licenses/ for more information. |
294
|
|
|
|
|
|
|
|
295
|
|
|
|
|
|
|
=cut |