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I am afraid you have it wrong. "Currying" and "higher-order functions" are two unrelated features that only have one thing in common: they often appear in functional languages. A function is "higher-order" if it accepts a function as it's parameter or if it returns a function (it "created").

Higher order functions are long supported by Perl 5, even though we usualy do not use that name. (I guess so that we do not scare people away. Higher-order functions sounds too "functional".)

sub Map { my $sub = shift(); my @new_arr; # want foreach my $item (@_) { push @new_arr, $sub->($item); } @new_arr; } sub foo {$_[0] + 1} @increased = Map \&foo, (1,2,3); print "@increased\n";
On the other hand a function is curried if it returns a "partialy applied" function if called with only the first few parameters. Of course then it is also higer-order actualy, but that's not the point.
sub Map { my $sub = shift(); if (@_) { # we are calling it normaly my @new_arr; # want foreach my $item (@_) { push @new_arr, $sub->($item); } return @new_arr; } else { # only the function is passed return sub { my @new_arr; # want foreach my $item (@_) { push @new_arr, $sub->($item); } return @new_arr; } } } sub foo {$_[0] + 1}; $inc = Map \&foo; @increased = $inc->(1,2,3); print "@increased\n";

(Next day) Actually ... the second function is not a good example. It's both curried and uncurried. If I wanted a plain curried version I'd define it as

sub Map { my $sub = shift(); return sub { my @new_arr; # want foreach my $item (@_) { push @new_arr, $sub->($item); } return @new_arr; } }
and then would call it either as
@incremented = Map(\&foo)->(1,2,3)
$Inc = Map(\&foo); @incremented = $Inc->(1,2,3)
As you can see the syntax is not too nice in Perl. Currying is a bit alien to Perl, it looks much more natural in modern functional languages.


In reply to Re: Re: Perl6 and Extreme Programming by Jenda
in thread Perl6 and Extreme Programming by Ovid

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    [GotToBTru]: late to the conversation .. but thanks, Corion, for the reminder about Perl::Tidy
    [Corion]: GotToBTru: Heh ;) I'm not really endorsing it, as I found that any gains made through it are easily squandered by the hours spent on configuring it. At least in my case :)
    [GotToBTru]: Like most Swiss Army Knives, you can cut yourself trying to find the blade you actually want
    [GotToBTru]: i am satisfied with the default settings turning the seemingly random formatting into something reliable
    [Corion]: GotToBTru: Yeah, I started a quick(ly implemented but slowly running) implementation of a program that would guess the "best" configuration (that is, least amount of changes) from my code, but then found that it stops parsing the source as soon as it ..
    [GotToBTru]: sadly, it can't do anything about this
    [Corion]: ... encounters sub foo($bar,$baz) {, which is something I like nowadays

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