/ 
Perl6-Parameters-0.01
River stage zero No dependents
/ Parameters

TITLE

Perl6::Parameters - Prototypes with named parameters

SYNOPSIS

use Perl6::Parameters;

sub foo($foo, ARRAY $bar; CODE $baz, *@others) {
	...
}

DESCRIPTION

Perl6::Parameters allows you to declare subroutines with named parameters in the Perl 6 style.

When you use this module and declare a subroutine with named parameters, this module modifies the subroutine, building a line-noise prototype and adding code to the subroutine to my any variables necessary and assign @_ into the parameter list.

Named Parameter Format

Most parameters are simple $varname; however, Perl6::Parameters also allows you access to the full power of Perl's built-in prototypes. Parameters are separated by a comma; a semicolon is also acceptable, and has the same meaning as a semicolon in Perl 5's prototypes.

Perl's prototypes allow you to automatically take a reference to a parameter by prefixing it with a backslash; Sub::Params::Named provides a way to access this. Parameters of the form TYPENAME $varname are automatically converted to the appropriate reference types. The list of supported TYPENAMEs follows:

TYPENAME | EQUIVALENT | DESCRIPTION
---------+------------+--------------------------------------------
REF      |     \.     | Auto-reference anything (NYI)
GLOB     |     \*     | Auto-reference a glob (for completeness)
CODE     |     &      | Auto-reference a code block
HASH     |     \%     | Auto-reference a hash
ARRAY    |     \@     | Auto-reference an array
REGEXP   |     /      | Auto-reference a regular expression (NYI)
SCALAR   |     \$     | Auto-reference a scalar
---------+------------+--------------------------------------------
         |            | In Perl 6 this would declare the type of
Anything |     $      |     the parameter; since Perl 5 doesn't 
else     |            |     have type declarations, it's treated as
         |            |     if the type name wasn't there.

(Items marked NYI have been proposed for inclusion into the Perl 5 core, but haven't happened yet. For now they're treated as $.)

Any parameter may be an array or hash; this will only take a literal array or hash. (It takes a reference to the array or hash being passed in, then dereferences it and assigns it to the array. Thus it will retain the actual size of the array being passed in.)

The last parameter may be an array or hash with a star (*) in front of it; this will be set to any parameters which haven't already been received.

CAVEATS

Although Perl 6 will pass paramters by constant reference, this module passes them by value. Appending is rw to a parameter in Perl 6 will make it a non-constant reference; however, this module dies if it sees an is rw in a prototype.

@_ keeps some of its special meaning; the result of using a prototype like ($foo, @_, $bar) is undefined. However, @_ may be used with the star prefix as the last parameter in the prototype.

BUGS

  • Quoted strings will still be modified by this module. This may or may not be a bug, depending on if you're evaling strings which define subroutines with Perl 6-style parameter lists in them.

There are likely other bugs lurking in this module; if you find one, send me an e-mail.

AUTHOR

Brent Dax <brentdax1@earthlink.net>

SPECIAL THANKS

Damian Conway, who wrote both of the modules I used to write this.

Larry Wall, for designing Perl 6. (Keep going Larry!)

My father, for letting me bounce ideas off him, even though he doesn't know Perl and probably doesn't care if I get this module done. :^)

COPYRIGHT

Copyright (C) 2001 Brent Dax. All Rights Reserved.

This module is free software. It may be used, redistributed and/or modified under the same terms as Perl itself.