sub::quote(3) [osx man page]

Sub::Quote(3)						User Contributed Perl Documentation					     Sub::Quote(3)

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 $x++ . "
" }, { '$x' =>  };

       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.

       options

       o no_install

	 Boolean.  Set this option to not install the generated coderef into the passed subroutine name on undefer.

   unquote_sub
	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.

   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.

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

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

	  print $x + $y . "
";
	}, '$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.

   capture_unroll
	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.

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.

perl v5.16.2							    2012-07-04							     Sub::Quote(3)

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Context::Preserve(3)					User Contributed Perl Documentation				      Context::Preserve(3)

NAME

       Context::Preserve - run code after a subroutine call, preserving the context the subroutine would have seen if it were the last statement
       in the caller

SYNOPSIS

       Have you ever written this?

	   my ($result, @result);

	   # run a sub in the correct context
	   if(!defined wantarray){
	       some::code();
	   }
	   elsif(wantarray){
	       @result = some::code();
	   }
	   else {
	       $result = some::code();
	   }

	   # do something after some::code
	   $_ += 42 for (@result, $result);

	   # finally return the correct value
	   if(!defined wantarray){
	       return;
	   }
	   elsif(wantarray){
	       return @result;
	   }
	   else {
	       return $result;
	   }

       Now you can just write this instead:

	 use Context::Preserve;

	 return preserve_context { some::code() }
		    after => sub { $_ += 42 for @_ };

DESCRIPTION

       Sometimes you need to call a function, get the results, act on the results, then return the result of the function.  This is painful
       because of contexts; the original function can behave different if it's called in void, scalar, or list context.  You can ignore the
       various cases and just pick one, but that's fragile.  To do things right, you need to see which case you're being called in, and then call
       the function in that context.  This results in 3 code paths, which is a pain to type in (and maintain).

       This module automates the process.  You provide a coderef that is the "original function", and another coderef to run after the original
       runs.  You can modify the return value (aliased to @_) here, and do whatever else you need to do.  "wantarray" is correct inside both
       coderefs; in "after", though, the return value is ignored and the value "wantarray" returns is related to the context that the original
       function was called in.

EXPORT

       "preserve_context"

FUNCTIONS

   preserve_context { original } [after|replace] => sub { after }
       Invokes "original" in the same context as "preserve_context" was called in, save the results, runs "after" in the same context, then
       returns the result of "original" (or "after" if "replace" is used).

       If the second argument is "after", then you can modify @_ to affect the return value.  "after"'s return value is ignored.

       If the second argument is "replace", then modifying @_ doesn't do anything.  The return value of "after" is returned from
       "preserve_context" instead.

       Run "preserve_context" like this:

	 sub whatever {
	     ...
	     return preserve_context { orginal_function() }
			after => sub { modify @_	  };
	 }

	 or

	 sub whatever {
	     ...
	     return preserve_context   { orginal_function() }
			replace => sub { return @new_return };
	 }

       Note that there's no comma between the first block and the "after =>" part.  This is how perl parses functions with the "(&@)" prototype.
       The alternative is to say:

	     preserve_context(sub { original }, after => sub { after });

       You can pick the one you like, but I think the first version is much prettier.

AUTHOR AND COPYRIGHT

       Jonathan Rockway "<jrockway@cpan.org>"

       Copyright (c) 2008 Infinity Interactive.  You may redistribute this module under the same terms as Perl itself.

perl v5.18.2							    2008-01-15						      Context::Preserve(3)

Linux and UNIX Man Pages

sub::quote(3) [osx man page]

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