Sub::Quote

Section: User Contributed Perl Documentation (3)
Updated: 2019-03-10
Page Index
 

NAME

Sub::Quote - Efficient generation of subroutines via string eval  

SYNOPSIS

 package Silly;

 use Sub::Quote qw(quote_sub unquote_sub quoted_from_sub);

 quote_sub 'Silly::kitty', q{ print "meow" };

 quote_sub 'Silly::doggy', q{ print "woof" };

 my $sound = 0;

 quote_sub 'Silly::dagron',
   q{ print ++$sound % 2 ? 'burninate' : 'roar' },
   { '$sound' => \$sound };

And elsewhere:

 Silly->kitty;  # meow
 Silly->doggy;  # woof
 Silly->dagron; # burninate
 Silly->dagron; # roar
 Silly->dagron; # burninate

 

DESCRIPTION

This package provides performant ways to generate subroutines from strings.  

SUBROUTINES

 

quote_sub

 my $coderef = quote_sub 'Foo::bar', q{ print $x++ . "\n" }, { '$x' => \0 };

Arguments: ?$name, $code, ?\%captures, ?\%options

$name is the subroutine where the coderef will be installed.

$code is a string that will be turned into code.

"\%captures" is a hashref of variables that will be made available to the code. The keys should be the full name of the variable to be made available, including the sigil. The values should be references to the values. The variables will contain copies of the values. See the ``SYNOPSIS'''s "Silly::dagron" for an example using captures.

Exported by default.

options

"no_install"
Boolean. Set this option to not install the generated coderef into the passed subroutine name on undefer.
"no_defer"
Boolean. Prevents a Sub::Defer wrapper from being generated for the quoted sub. If the sub will most likely be called at some point, setting this is a good idea. For a sub that will most likely be inlined, it is not recommended.
"package"
The package that the quoted sub will be evaluated in. If not specified, the package from sub calling "quote_sub" will be used.
"hints"
The value of $^H to use for the code being evaluated. This captures the settings of the strict pragma. If not specified, the value from the calling code will be used.
"warning_bits"
The value of "${^WARNING_BITS}" to use for the code being evaluated. This captures the warnings set. If not specified, the warnings from the calling code will be used.
"%^H"
The value of "%^H" to use for the code being evaluated. This captures additional pragma settings. If not specified, the value from the calling code will be used if possible (on perl 5.10+).
"attributes"
The ``Subroutine Attributes'' in perlsub to apply to the sub generated. Should be specified as an array reference. The attributes will be applied to both the generated sub and the deferred wrapper, if one is used.
"file"
The apparent filename to use for the code being evaluated.
"line"
The apparent line number to use for the code being evaluated.
 

unquote_sub

 my $coderef = unquote_sub $sub;

Forcibly replace subroutine with actual code.

If $sub is not a quoted sub, this is a no-op.

Exported by default.  

quoted_from_sub

 my $data = quoted_from_sub $sub;

 my ($name, $code, $captures, $compiled_sub) = @$data;

Returns original arguments to quote_sub, plus the compiled version if this sub has already been unquoted.

Note that $sub can be either the original quoted version or the compiled version for convenience.

Exported by default.  

inlinify

 my $prelude = capture_unroll '$captures', {
   '$x' => 1,
   '$y' => 2,
 }, 4;

 my $inlined_code = inlinify q{
   my ($x, $y) = @_;

   print $x + $y . "\n";
 }, '$x, $y', $prelude;

Takes a string of code, a string of arguments, a string of code which acts as a ``prelude'', and a Boolean representing whether or not to localize the arguments.  

quotify

 my $quoted_value = quotify $value;

Quotes a single (non-reference) scalar value for use in a code string. Numbers aren't treated specially and will be quoted as strings, but undef will quoted as "undef()".  

capture_unroll

 my $prelude = capture_unroll '$captures', {
   '$x' => 1,
   '$y' => 2,
 }, 4;

Arguments: $from, \%captures, $indent

Generates a snippet of code which is suitable to be used as a prelude for ``inlinify''. $from is a string will be used as a hashref in the resulting code. The keys of %captures are the names of the variables and the values are ignored. $indent is the number of spaces to indent the result by.  

qsub

 my $hash = {
  coderef => qsub q{ print "hello"; },
  other   => 5,
 };

Arguments: $code

Works exactly like ``quote_sub'', but includes a prototype to only accept a single parameter. This makes it easier to include in hash structures or lists.

Exported by default.  

sanitize_identifier

 my $var_name = '$variable_for_' . sanitize_identifier('@name');
 quote_sub qq{ print \$${var_name} }, { $var_name => \$value };

Arguments: $identifier

Sanitizes a value so that it can be used in an identifier.  

ENVIRONMENT

 

SUB_QUOTE_DEBUG

Causes code to be output to "STDERR" before being evaled. Several forms are supported:
1
All subs will be output.
"/foo/"
Subs will be output if their code matches the given regular expression.
"simple_identifier"
Any sub with the given name will be output.
"Full::identifier"
A sub matching the full name will be output.
"Package::Name::"
Any sub in the given package (including anonymous subs) will be output.
 

CAVEATS

Much of this is just string-based code-generation, and as a result, a few caveats apply.  

return

Calling "return" from a quote_sub'ed sub will not likely do what you intend. Instead of returning from the code you defined in "quote_sub", it will return from the overall function it is composited into.

So when you pass in:

   quote_sub q{  return 1 if $condition; $morecode }

It might turn up in the intended context as follows:

  sub foo {

    <important code a>
    do {
      return 1 if $condition;
      $morecode
    };
    <important code b>

  }

Which will obviously return from foo, when all you meant to do was return from the code context in quote_sub and proceed with running important code b.  

pragmas

"Sub::Quote" preserves the environment of the code creating the quoted subs. This includes the package, strict, warnings, and any other lexical pragmas. This is done by prefixing the code with a block that sets up a matching environment. When inlining "Sub::Quote" subs, care should be taken that user pragmas won't effect the rest of the code.  

SUPPORT

Users' IRC: #moose on irc.perl.org

Development and contribution IRC: #web-simple on irc.perl.org

Bugtracker: <https://rt.cpan.org/Public/Dist/Display.html?Name=Sub-Quote>

Git repository: <git://github.com/moose/Sub-Quote.git>

Git browser: <https://github.com/moose/Sub-Quote>  

AUTHOR

mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>  

CONTRIBUTORS

frew - Arthur Axel ``fREW'' Schmidt (cpan:FREW) <frioux@gmail.com>

ribasushi - Peter Rabbitson (cpan:RIBASUSHI) <ribasushi@cpan.org>

Mithaldu - Christian Walde (cpan:MITHALDU) <walde.christian@googlemail.com>

tobyink - Toby Inkster (cpan:TOBYINK) <tobyink@cpan.org>

haarg - Graham Knop (cpan:HAARG) <haarg@cpan.org>

bluefeet - Aran Deltac (cpan:BLUEFEET) <bluefeet@gmail.com>

ether - Karen Etheridge (cpan:ETHER) <ether@cpan.org>

dolmen - Olivier Mengué (cpan:DOLMEN) <dolmen@cpan.org>

alexbio - Alessandro Ghedini (cpan:ALEXBIO) <alexbio@cpan.org>

getty - Torsten Raudssus (cpan:GETTY) <torsten@raudss.us>

arcanez - Justin Hunter (cpan:ARCANEZ) <justin.d.hunter@gmail.com>

kanashiro - Lucas Kanashiro (cpan:KANASHIRO) <kanashiro.duarte@gmail.com>

djerius - Diab Jerius (cpan:DJERIUS) <djerius@cfa.harvard.edu>  

COPYRIGHT

Copyright (c) 2010-2016 the Sub::Quote ``AUTHOR'' and ``CONTRIBUTORS'' as listed above.  

LICENSE

This library is free software and may be distributed under the same terms as perl itself. See <http://dev.perl.org/licenses/>.


 

Index

NAME
SYNOPSIS
DESCRIPTION
SUBROUTINES
quote_sub
unquote_sub
quoted_from_sub
inlinify
quotify
capture_unroll
qsub
sanitize_identifier
ENVIRONMENT
SUB_QUOTE_DEBUG
CAVEATS
return
pragmas
SUPPORT
AUTHOR
CONTRIBUTORS
COPYRIGHT
LICENSE
LinuxReviews : manual page archive : man3pm