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signatures.3pm

NAME

signatures - subroutine signatures with no source filter

SYNOPSIS

     use signatures;
 
     sub foo ($bar, $baz) {
         return $bar + $baz;
     }
 
 

DESCRIPTION

With this module, we can specify subroutine signatures and have variables automatically defined within the subroutine.

For example, you can write

     sub square ($num) {
         return $num * $num;
     }
 
 

and it will be automatically turned into the following at compile time:

     sub square {
         my ($num) = @_;
         return $num * $num;
     }
 
 

Note that, although the syntax is very similar, the signatures provided by this module are not to be confused with the prototypes described in perlsub. All this module does is extracting items of @_ and assigning them to the variables in the parameter list. No argument validation is done at runtime.

The signature definition needs to be on a single line only.

If you want to combine sub signatures with regular prototypes a "proto" attribute exists:

     sub foo ($bar, $baz) : proto($$) { ... }
 
 

METHODS

If you want subroutine signatures doing something that this module doesn't provide, like argument validation, typechecking and similar, you can subclass it and override the following methods.

proto_unwrap ($prototype)

Turns the extracted $prototype into code.

The default implementation returns "my (${prototype}) = @_;" or an empty string, if no prototype is given.

inject ($offset, $code)

Inserts a $code string into the line perl currently parses at the given $offset. This is only called by the "callback" method.

callback ($offset, $prototype)

This gets called as soon as a sub definition with a prototype is encountered. Arguments are the $offset within the current line perl is parsing and extracted $prototype.

The default implementation calls "proto_unwrap" with the prototype and passes the returned value and the offset to "inject".

BUGS

prototypes aren't checked for validity yet

You won't get a warning for invalid prototypes using the "proto" attribute, like you normally would with warnings enabled.

you shouldn't alter $SIG{__WARN__} at compile time

After this module is loaded you shouldn't make any changes to $SIG{__WARN__} during compile time. Changing it before the module is loaded or at runtime is fine.

SEE ALSO

Method::Signatures

MooseX::Method::Signatures

Sub::Signatures

Attribute::Signature

Perl6::Subs

Perl6::Parameters

AUTHOR

Florian Ragwitz <rafl@debian.org>

THANKS

Moritz Lenz and Steffen Schwigon for documentation review and improvement.

COPYRIGHT AND LICENSE

Copyright (c) 2008 Florian Ragwitz

This module is free software.

You may distribute it under the same license as Perl itself.