NAME

       Function::Parameters::Info - Information about parameter lists

SYNOPSIS

         use Function::Parameters;

         fun foo($x, $y, :$hello, :$world = undef) {}

         my $info = Function::Parameters::info \&foo;
         my @p0 = $info->invocants;            # ()
         my @p1 = $info->positional_required;  # ('$x', '$y')
         my @p2 = $info->positional_optional;  # ()
         my @p3 = $info->named_required;       # ('$hello')
         my @p4 = $info->named_optional;       # ('$world')
         my $p5 = $info->slurpy;               # undef
         my $min = $info->args_min;  # 4
         my $max = $info->args_max;  # inf

         my @invocants = Function::Parameters::info(method () { 42 })->invocants;
         # ('$self')

         my $slurpy = Function::Parameters::info(fun (@) {})->slurpy;  # '@'

DESCRIPTION

       "Function::Parameters::info" returns objects of this class to describe parameter lists of
       functions. See below for "Parameter Objects".  The following methods are available:

       $info->invocants

       Returns a list of parameter objects for the variables into which initial arguments are
       "shift"ed automatically (or a count in scalar context). This will usually return "()" for
       normal functions and "('$self')" for methods.

       $info->positional_required

       Returns a list of parameter objects for the required positional parameters (or a count in
       scalar context).

       $info->positional_optional

       Returns a list of parameter objects for the optional positional parameters (or a count in
       scalar context).

       $info->named_required

       Returns a list of parameter objects for the required named parameters (or a count in
       scalar context).

       $info->named_optional

       Returns a list of parameter objects for the optional named parameters (or a count in
       scalar context).

       $info->slurpy

       Returns a parameter object for the final array or hash that gobbles up all remaining
       arguments, or "undef" if no such thing exists.

       $info->args_min

       Returns the minimum number of arguments this function requires. This is computed as
       follows: Invocants and required positional parameters count 1 each.  Optional parameters
       don't count. Required named parameters count 2 each (key + value). Slurpy parameters don't
       count either because they accept empty lists.

       $info->args_max

       Returns the maximum number of arguments this function accepts. This is computed as
       follows: If there are any named or slurpy parameters, the result is "Inf".  Otherwise the
       result is the number of all invocants and positional parameters.

       $info->invocant

       Similar to "$info->invocants" above: Returns "undef" if the number of invocants is 0, a
       parameter object for the invocant if there is exactly 1, and throws an exception
       otherwise.

       Parameter Objects

       Many of the methods described above return parameter objects.  These objects have two
       methods: "name", which returns the name of the parameter (as a plain string), and "type",
       which returns the corresponding type constraint object (or undef if there was no type
       specified).

       This should be invisible if you don't care about types because the objects also overload
       stringification to call "name". That is, if you treat parameter objects like strings, they
       behave like strings (i.e. their names).

SEE ALSO

       Function::Parameters

AUTHOR

       Lukas Mai, "<l.mai at web.de>"

COPYRIGHT & LICENSE

       Copyright 2013, 2016 Lukas Mai.

       This program is free software; you can redistribute it and/or modify it under the terms of
       either: the GNU General Public License as published by the Free Software Foundation; or
       the Artistic License.

       See http://dev.perl.org/licenses/ for more information.