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# You may distribute under the terms of either the GNU General Public License |
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# or the Artistic License (the same terms as Perl itself) |
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# |
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# (C) Paul Evans, 2022 -- leonerd@leonerd.org.uk |
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package Syntax::Keyword::Inplace 0.01; |
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use v5.14; |
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use warnings; |
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use Carp; |
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require XSLoader; |
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XSLoader::load( __PACKAGE__, our $VERSION ); |
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=head1 NAME |
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C - syntax for making inplace changes to variables |
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=head1 SYNOPSIS |
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use Syntax::Keyword::Inplace; |
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my $var = "some value here"; |
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inplace uc $var; # equivalent to $var = uc $var; |
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print $var; # prints "SOME VALUE HERE" |
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=head1 DESCRIPTION |
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This module provides a syntax plugin that implements a single keyword, |
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C, which acts on function calls (or function-like perl operators) |
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to make them modify the target expression. |
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Perl has a large number of function-like operators that look at a single |
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expression argument and return some new value based on it. Sometimes the |
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result of calling one of these is immediately assigned back into the same |
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variable again, in code that looks like C<$var = func($var)>. It is for these |
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situations where this module is intended to apply. |
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=cut |
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=head1 KEYWORDS |
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=head2 inplace |
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inplace FUNC( EXPR ) |
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The C keyword modifies the behaviour of the following expression, |
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which must be a function call or function-like core perl operator, which takes |
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exactly one argument. That single argument must be valid as an lvalue (i.e. |
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the target of an assignment). At runtime the function is called on that |
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argument expression and the result of the function call is stored back into |
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that expression. |
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my $var = ...; |
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inplace foo( $var ); # equivalent to $var = foo( $var ) |
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If the expression is more complex than a single variable directly, then any |
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side-effects involved in generating it only happen once. |
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inplace foo( $hash{some_function_call()} ); |
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# equivalent to |
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# my $tmp_key = some_function_call(); |
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# $hash{$tmp_key} = foo( $hash{$tmp_key} ); |
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=cut |
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sub import |
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{ |
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my $class = shift; |
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my $caller = caller; |
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$class->import_into( $caller, @_ ); |
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} |
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sub import_into |
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{ |
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my $class = shift; |
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my ( $caller, @syms ) = @_; |
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my %syms = map { $_ => 1 } @syms; |
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$^H{"Syntax::Keyword::Inplace/inplace"}++; |
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croak "Unrecognised import symbols @{[ keys %syms ]}" if keys %syms; |
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} |
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=head1 AUTHOR |
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Paul Evans |
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=cut |
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0x55AA; |