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package Scalar::IfDefined; |
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use 5.006; |
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use strict; |
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use warnings; |
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use Scalar::Util qw/blessed reftype/; |
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use Exporter 'import'; |
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1196
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our @EXPORT_OK = qw/ifdef $ifdef/; |
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=head1 NAME |
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Scalar::IfDefined - Apply block to scalar depending on if it's defined. |
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=cut |
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our $VERSION = '0.06'; |
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=head1 SYNOPSIS |
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use Scalar::IfDefined qw/ifdef/; |
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my $hash = { |
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a => 1, |
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b => 2, |
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c => 3, |
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d => { |
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E => 1, |
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F => 2, |
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}, |
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}; |
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ifdef { $_ + 1 } $hash->{a}; # ---> 2 |
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ifdef { $_ + 1 } $hash->{missing}; # ---> undef |
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ifdef { $_ + 1 } ifdef { $_->{F} } $hash->{d}; # ---> 3 |
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ifdef { $_ + 1 } ifdef { $_->{MISSING} } $hash->{d}; # ---> undef |
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# Or perhaps with Perl6::Flows |
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use Perl6::Flows; |
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my $result = ( |
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$hash->{a} |
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==> ifdef { $_->{F} } |
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==> ifdef { $_ + 1 } |
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); # ---> 3 |
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=head1 EXPORT |
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=over 4 |
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53
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=item ifdef |
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=item $ifdef |
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=back |
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=head1 SUBROUTINES/METHODS |
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=head2 ifdef |
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Takes a block and a scalar value. |
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If the scalar value is undef, the block is ignored and undef is returned |
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straight away. |
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If the scalar value is defined, then the block is evaluated with $_ as |
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the value passed in, and the result of the block is returned. |
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=cut |
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sub ifdef(&$) { |
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my ($block, $scalar) = @_; |
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return $scalar if not defined $scalar; |
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1
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return $block->($scalar) for $scalar; |
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} |
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=head2 $ifdef |
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Used to dereference a possibly-undef scalar. |
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If the scalar is undef, returns undef. |
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If the scalar is an object, the first argument is the method to call, and the |
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rest of the arguments are the method arguments. |
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If the scalar is an array ref, the first argument is used to index into the |
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array. |
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If the scalar is a hash ref, the first argument is used to access the hash. |
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If the scalar is a code ref, the code ref is run with all the arguments. |
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As a special case, if the first argument is a code ref, it will be run with the |
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scalar as the first argument and the other arguments as the rest. This form |
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allows you to use C<$ifdef> on a simple scalar - but you might be better off |
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with C itself for that. |
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The following uses will all return undef if the C<$scalar> is undef, or The |
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Right Thing if not. |
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# Run "method_name" on $obj, if $obj is defined. |
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$obj->$ifdef("method_name", "argument", "argument"); |
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# Run $coderef with two arguments if $coderef is defined. |
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$coderef->$ifdef("argument", "argument"); |
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# Lowercase the zeroth element of the arrayref, or undef if either of those |
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# things is undef. |
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$arrayref->$ifdef(0)->$ifdef(sub { lc }); |
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# Call "method_name" on $hashref->{object}, or return undef if either of |
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# those is undef |
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$hashref->$ifdef('object')->$ifdef('method_name'); |
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118
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=cut |
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120
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our $ifdef = sub { |
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my $obj = shift; |
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my ($method, @args) = @_; |
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return undef if not defined $obj; |
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return $obj->$method(@args) if blessed $obj or reftype $method eq 'CODE'; |
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return $obj->[$method] if reftype $obj eq 'ARRAY'; |
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return $obj->{$method} if reftype $obj eq 'HASH'; |
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return $obj->($method, @args) if reftype $obj eq 'CODE'; |
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die "Can't getdef on " . reftype $obj; |
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}; |
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135
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=head1 AUTHOR |
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Nick Booker, C<< >> |
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=head1 BUGS |
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L |
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144
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=head1 ACKNOWLEDGEMENTS |
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146
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=head2 Alastair McGowan-Douglas (ALTREUS) |
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For developing the C<$ifdef> (coderef) form. |
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150
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=head1 LICENSE AND COPYRIGHT |
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152
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Copyright (C) 2015 Nick Booker |
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This program is free software; you can redistribute it and/or modify it |
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under the terms of either: the GNU General Public License as published |
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by the Free Software Foundation; or the Artistic License. |
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See http://dev.perl.org/licenses/ for more information. |
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=cut |
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1; # End of Scalar::IfDefined |