Re^2: Near-free function currying in Perl

[dragonchild]

package AutoCurry;
require v5.6.1;
use Attribute::Handlers::Prospective;

sub UNIVERSAL::curry : ATTR(CODE,RAWDATA) {
    my ($package, $symbol, $referent, $attr, $data, $phase) = @_;

    my $num = () = $data =~ /(\$)/g;
    *{"$package".'::'.*{$symbol}{NAME}} = sub {
        if (@_ < $num) {
            my @x = @_;
            return sub { $referent->(@x, @_ ) };
        }
        $referent->(@_);
    };
}

1;
__END__

#############
demo.pl
#############

#!perl

use strict;
use warnings;

use AutoCurry;

sub foo : curry($$$) {
    print "Hello @_\n";
};

foo( 'a', 'b', 'c' );
my $ref = foo('d','e');

$ref->('f');
$ref->('g');

Obviously, improvements can be made, but I think this does what is desired. There is a slight performance penalty, but it's not bad at all.

[stvn]

LOL, you beat me by only a few minutes, I was just going to posts this.

Read more... (1438 Bytes)

Although to be honest, neither of our implementations, nor Tom's do what Haskell and Standard ML do, which is too keep currying until all the functions arguments are satisfied.

my $curried_foo = foo(1);
my $even_more_curried_foo = $curried_foo->(2);
print $even_more_curried_foo->(3); # now we execute the function

And from my (limited) understanding of prototypes, it seems that this may not be possible since seems it is difficult to assign an attribute to a closure.

[dragonchild]

Easily fixed.

package Demo;
require v5.6.1;
use Attribute::Handlers::Prospective;

sub UNIVERSAL::curry : ATTR(CODE,RAWDATA) {
    my ($package, $symbol, $referent, $attr, $data, $phase) = @_;

    my $num = () = $data =~ /(\$)/g;
    my $subname = "$package".'::'.*{$symbol}{NAME};
    *$subname = sub {
        if (@_ < $num) {
            my @x = @_;
            return sub { $subname->(@x, @_ ) };
        }
        $referent->(@_);
    };
}

1;
__END__

[stvn]

Very nice ++