Gain performances and fix some issues using XS

Hello porters,

I would like to improve a module and have the feeling there is nothing
I can do in pure perl so I post here to get advices. I apologize if
I missused the list: please let me know.

Thanks for any help and regards.
Marc

__DATA__

I discovered [haskell](https://fr.wikipedia.org/wiki/Haskell) in the
mid 2000 but never had the chance to put it at work. I wanted to
get the similar logic in Perl so I wrote https://metacpan.org/pod/Perlude,
presented it at French Perl Workshop ('10?) and YAPC::Europe'11.

Book and Dolmen helped me to polish the thing and experimented a lazy
version of Perlude (which is only "on demand", like unix pipes) then it
remains untouched for many years. I tought I was the last one to use it but
I noticed someone made a debian package out of it.

This module was good enough for me to use it without feeling the need to
improve it since then but now I have larger and larger datasets the
known performance issue of perlude hurts. This issue is known and
I declared I was unable to fix it at the time because Perlude is
based on anonymous subroutines returning scalars in an list context (so
the end of a stream is () which is a very functionnal programming
thing). I don't know how to mesure what costs the most. I remember I
tried to use some profilers but I was unable to understand the result
because everything happened in __ANON__ (AFAIR).

Since then I discovered C and try to give XS a chance (also because I
would like to bind some fortran libraries at some point) so I would like
to investigate the only 3 anoying things I have with Perlude and I
wonder if XS could be a solution (as I found none in PP):

1. make it faster at execution
2. make it even faster/easy to write with expressions instead blocks
   with filter/apply (which are "on demand" conterparts of grep/map).
3. put a value back to the stream in case of failure

eg.

	use Perlude;
	sub fibo {
		my @seed = @_;
		sub {
			push @seed, $seed[0] + $seed[1];
			shift @seed;
		}
	}
	my $fib = fibo 1, 1;
	print join ",", fold takeWhile {$_ < 50} $fib;
	print " then ...", $fib->();

problem 3:

	# fibo: 1,1,2,3,5,8,13,21,34,55,89
	# current output
	# 1,1,2,3,5,8,13,21,34 then ...89
	# ideal output
	# 1,1,2,3,5,8,13,21,34 then ...55

problem 2:

current version:

	# with expressions intead blocks
	print join ",", fold takeWhile {$_ < 50} $fib;

	# I wonder if there is a trick to make fold useless
	print join ",", fold takeWhile $_ < 50, $fib;

	# or overload an operator for subroutines to fold
	print join ",", @< takeWhile $_ < 50, $fib;

-- 
Marc Chantreux
Pôle CESAR (Calcul et services avancés à la recherche)
Université de Strasbourg
☎  03.68.85.60.79