Matt S Trout > Moo-1.000008 > Sub::Quote



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Source   Latest Release: Moo-2.002005


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


 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


This package provides performant ways to generate subroutines from strings.



 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. See the "SYNOPSIS"'s Silly::dagron for an example using captures.



 my $coderef = unquote_sub $sub;

Forcibly replace subroutine with actual code. Note that for performance reasons all quoted subs declared so far will be globally unquoted/parsed in a single eval. This means that if you have a syntax error in one of your quoted subs you may find out when some other sub is unquoted.

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


 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.


 my $prelude = capture_unroll {
   '$x' => 1,
   '$y' => 2,

 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.


 my $prelude = capture_unroll {
   '$x' => 1,
   '$y' => 2,

Generates a snippet of code which is suitable to be used as a prelude for "inlinify". The keys are the names of the variables and the values are (duh) the values. Note that references work as values.


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


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;
    <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.

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