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Re^3: Near-free function currying in Perl

by stvn (Monsignor)
on Nov 17, 2004 at 17:11 UTC ( #408481=note: print w/replies, xml ) Need Help??

in reply to Re^2: Near-free function currying in Perl
in thread Near-free function currying in Perl

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

#!/usr/bin/perl use strict; use warnings; use Test::More tests => 3; { package Test; use Attribute::Handlers; sub curry : ATTR(CODE) { my ($package, $symbol, $referent, $attr, $data, $phase) = @_; my @args = split(//, $data); my $num_args = scalar(@args); my $func = *{$symbol}{NAME}; no strict 'refs'; no warnings 'redefine'; *{"${package}::${func}"} = sub { if (scalar(@_) == $num_args) { goto $referent; } else { my @args = @_; return sub { $referent->(@args, @_); }; } }; } sub foo : curry('$$$') { return @_; } } is_deeply( [ Test::foo(1, 2, 3) ], [ 1, 2, 3 ], '... got the right return value'); my $curried_foo = Test::foo(1, 2); is(ref($curried_foo), 'CODE', '... this is our curried sub'); is_deeply( [ $curried_foo->(3) ], [ 1, 2, 3 ], '... got the right return value now'); 1;

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.


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Re^4: Near-free function currying in Perl
by dragonchild (Archbishop) on Nov 17, 2004 at 17:33 UTC
    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__

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      Very nice ++


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