Sub::Defer(3) User Contributed Perl Documentation Sub::Defer(3)NAME
Sub::Defer - defer generation of subroutines until they are first called
SYNOPSIS
use Sub::Defer;
my $deferred = defer_sub 'Logger::time_since_first_log' => sub {
my $t = time;
sub { time - $t };
};
Logger->time_since_first_log; # returns 0 and replaces itself
Logger->time_since_first_log; # returns time - $t
DESCRIPTION
These subroutines provide the user with a convenient way to defer creation of subroutines and methods until they are first called.
SUBROUTINES
defer_sub
my $coderef = defer_sub $name => sub { ... };
This subroutine returns a coderef that encapsulates the provided sub - when it is first called, the provided sub is called and is -itself-
expected to return a subroutine which will be goto'ed to on subsequent calls.
If a name is provided, this also installs the sub as that name - and when the subroutine is undeferred will re-install the final version
for speed.
undefer_sub
my $coderef = undefer_sub &Foo::name;
If the passed coderef has been deferred this will "undefer" it. If the passed coderef has not been deferred, this will just return it.
If this is confusing, take a look at the example in the "SYNOPSIS".
undefer_all
undefer_all();
This will undefer all defered subs in one go. This can be very useful in a forking environment where child processes would each have to
undefer the same subs. By calling this just before you start forking children you can undefer all currently deferred subs in the parent so
that the children do not have to do it.
SUPPORT
See Moo for support and contact information.
AUTHORS
See Moo for authors.
COPYRIGHT AND LICENSE
See Moo for the copyright and license.
perl v5.18.2 2013-12-31 Sub::Defer(3)
Check Out this Related 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. 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.
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.
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 $prelude = capture_unroll '$captures', {
'$x' => 1,
'$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 $prelude = capture_unroll '$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.
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
See Moo for support and contact information.
AUTHORS
See Moo for authors.
COPYRIGHT AND LICENSE
See Moo for the copyright and license.
perl v5.18.2 2013-12-31 Sub::Quote(3)