package PDL::NamedArgs;
use 5.006;
#use strict;
use warnings;
require Exporter;
our @ISA = qw(Exporter);
# Items to export into callers namespace by default. Note: do not export
# names by default without a very good reason. Use EXPORT_OK instead.
# Do not simply export all your public functions/methods/constants.
# This allows declaration use PDL::NamedArgs ':all';
# If you do not need this, moving things directly into @EXPORT or @EXPORT_OK
# will save memory.
our %EXPORT_TAGS = ( 'all' => [ qw(
parseArgs
) ] );
our @EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } );
our @EXPORT = qw(
parseArgs
);
our $VERSION = '0.12';
sub parseArgs
{
my($funcDef)=shift;
my(%named,@unnamed,@arg_names);
my($status,$i)=(0);
# Build up the arg_names array and the arg_defaults hash
for $i (split(/[ ,]+/,$funcDef))
{
if ($i =~ m/^([a-zA-Z]\w*)=(.*)$/)
{ push(@arg_names,lc($1)); $arg_defaults{lc($1)}=$2; }
else
{ push(@arg_names,lc($i)); }
}
# Walk thru the arguments passed and separate into %named & @unnamed arguments
while ($#_>=0)
{
$i=shift;
if (!ref($i) && grep(/^$i$/i,@arg_names)) # Named argument
{
if (exists($named{$i}))
{ return ("Error: Argument $i multiple definitions"); } # Whoops, somebody went overboard...
$named{$i}=shift;
}
else # Unnamed argument
{ push @unnamed,$i; }
}
# Walk thru the argument names & make sure they are set, if not use the default if defined
for $i (@arg_names)
{
if (exists($named{$i})) # Argument already defined via named argument (Priority #1)
{ next; }
# Argument is not defined
if (@unnamed)
{ $named{$i}=shift(@unnamed); } # Grab one of the unnamed list if available (Priority #2)
elsif (exists($arg_defaults{$i}))
{ $named{$i}=$arg_defaults{$i}; } # Set to the default value if defined (Priority #3)
else
{ return ("Error: Missing $i argument"); } # Whoops, somebody forgot something...
}
if (@unnamed)
{ return ("Error: Too many arguments"); } # Whoops, somebody went overboard...
return ($status,%named);
}
1;
__END__
# Below is stub documentation for your module. You better edit it!
=head1 NAME
PDL::NamedArgs - Perl extension for named & unamed arguments
with optional default values
=head1 SYNOPSIS
use PDL::NamedArgs;
=head1 OVERVIEW
PDL::NamedArgs (currently) exports one main function which
aids in the processing of function arguments. The key
differentiators with this module in comparison to others
on CPAN is that it allows any combination of named & unnamed
arguments while also providing optional support for
default values. I like to think of it as varargs on steroids...
=head1 DETAILED DESCRIPTION
=head2 parseArgs Synopsis
parseArgs($funcDef,@_)
$funcDef - Function definition that lists all arguments
(In order!!) with default values, separated
by either space or comma.
Examples "x min max" or "x,min=0,max=10"
@_ - Arguments to parse, subject to $funcDef
Returns ($result,%named)
$status - Result of parsing. 0 if ok, otherwise set
to error message
%named - Hash of argument names set to appropriate
values after argument parsing
=head2 parseArgs Description
The goal of this utility function is to allow more
flexibility with how passed arguments are handled
when calling a function. I guess the best way to
describe this is to give an example.
Consider a function with following abstract prototype
pbinom(q, size, prob, lower_tail=1, log_p=0)
In a language such as R you could call this function
in any of the following formats and receive the exact
same result.
pbinom(.5, 50, 3,1,1) # All arguments specified
pbinom(.5,size=50,3,log_p=1) # lower_tail set to default value
# and using named values
pbinom(prob=3,q=.5,size=50) # Using default values, named values
# & mixing up the order
We can achieve almost the same capabilties of R in perl
by using the parseArgs function for parsing arguments and
by changing the named variable syntax to name=>value.
The $funcDef for pbinom function would be
'q, size, prob, lower_tail=1, log_p=0' and an example
implementation of pbinom using parseArgs might look like
sub pbinom
{
my($status,%argHash)=
parseArgs('q, size, prob, lower_tail=1, log_p=0'
,@_);
die ("pbinom error\n$status\n") if $status;
print "(q, size, prob, lower_tail, log_p) = ";
print "($argHash{q}, $argHash{size}, $argHash{prob},
$argHash{lower_tail}, $argHash{log_p})\n";
}
We could then call pbinom in perl by any of the following
equivalent methods
pbinom(.5, 50, 3,1,0); # All arguments specified
pbinom(.5,size=>50,3,log_p=>0); # lower_tail set to default value
# and using named values
pbinom(prob=>3,q=>.5,size=>50); # Using default values, named values
# & mixing up the order
=head2 Misc Notes
All argument names are set to lowercase as a way to allow
case insensitivity, thus pbinom(PROB=>3,q=>.5,SiZe=>50)
would also work, but the returned hash would only have
keys that are lowercase
Priority of argument assignment
1. Named argument
2. Unnamed ordered argument
3. Default argument values
=head1 AUTHOR
John Cavanaugh, E<lt>cavanaug@users.sourceforge.netE<gt>
=head1 SEE ALSO
L<perl>.
=cut