![sort
F(a, a), [a] --------> [a]](https://image.slidesharecdn.com/functionalperl-130101190232-phpapp02/85/Functional-perl-14-320.jpg)
![@sorted_list
= sort {$_[0] <=> $_[1]} @list](https://image.slidesharecdn.com/functionalperl-130101190232-phpapp02/85/Functional-perl-15-320.jpg)
![sort {
@a = split ///, $a;
@b = split ///, $b;
($a[2] <=> $b[2])
|| ($a[1] <=> $b[1])
|| ($a[0] <=> $b[0])
|| 0;
} @list_of_dmy_dates](https://image.slidesharecdn.com/functionalperl-130101190232-phpapp02/85/Functional-perl-19-320.jpg)
![grep
F(a, a), [a] --------> [a]](https://image.slidesharecdn.com/functionalperl-130101190232-phpapp02/85/Functional-perl-21-320.jpg)
![map
F(a), [a] --------> [a]](https://image.slidesharecdn.com/functionalperl-130101190232-phpapp02/85/Functional-perl-22-320.jpg)
![List::Util
reduce
F(a, b) → b, [a] --------------> b](https://image.slidesharecdn.com/functionalperl-130101190232-phpapp02/85/Functional-perl-25-320.jpg)
Functional perl
- 1. Functional Programming Perl Christopher Mckay [email protected]
- 2. What Am I
- 3. What's this talk all about?
- 4. History
- 5. How
- 6. Why not?
- 7. But I don't use/appreciate/like perl?
- 8. Functional Programming is Easy
- 9. So easy sysadmins do it
- 12. Wrote Pearl Perl
- 13. People wanted a sort function Larry was generous
- 14. sort F(a, a), [a] --------> [a]
- 15. @sorted_list = sort {$_[0] <=> $_[1]} @list
- 16. @sorted_list = sort {$a <=> $b } @list
- 17. @sorted_list = sort {$a <=> $b} @list
- 18. sort String sorting sort {$a cmp $b} Also string sorting sort {$a <=> $b} Sort numerically sort &comparator Sort by function named comparator
- 19. sort { @a = split ///, $a; @b = split ///, $b; ($a[2] <=> $b[2]) || ($a[1] <=> $b[1]) || ($a[0] <=> $b[0]) || 0; } @list_of_dmy_dates
- 20. 1988 - Perl 2.0 1989 - Perl 3.0 1991 - Perl 4.0
- 21. grep F(a, a), [a] --------> [a]
- 22. map F(a), [a] --------> [a]
- 23. 1994 – Perl 5.0
- 24. memoize F(a) → b --------------> F(a) → b
- 25. List::Util reduce F(a, b) → b, [a] --------------> b
- 26. List::MoreUtils any, all, none, notall, true, false, firstidx, first_index, lastidx, part, mesh, last_index, insert_after, zip, uniq, apply, indexes, after, after_incl, before, before_incl, firstval, first_value, lastval, last_value, pairwise, distinct, minmax
- 28. So Perl evolved a functional theme
- 29. So how do I make functional stuff in perl instead of just using it?
- 30. Lexical scoping
- 32. That's about it. Your language does that too right?
- 33. So lets write a function that rolls a die
- 34. my $dx = sub { my ($sides) = @_; return (rand() * $sides) + 1; } my $roll = $dx->(6);
- 35. I don't like rolling 1's though so...
- 36. my $cheat = sub { my ($roll) = @_; if ($roll < 2) { return 2; } else { return $roll; } }
- 37. I don't want to get caught turning the die over though so ...
- 38. my $inconspicuous_dx = sub { my ($sides) = @_; return $cheat->($dx->($sides)); }
- 39. my $compose = sub { my ($fa, $fb) = @_; return sub { return $fa->($fb->(@_)); } }
- 40. my $inconspicuous_dx = $compose->($cheat, $dx); my $better_roll = $inconspicuous_dx->(6);
- 41. Monads in Perl Masahiro Honma (hiratara) YAPC::Asia 2011 Slides are in english Data::Monad
- 42. All I ever need is d6!
- 43. my $d6 = sub { return $inconspicuous_dx->(6); }; my $roll_a_6 = $d6->();
- 44. Too lazy to roll 20d6
- 45. my $dice_tower_maker = sub { my ($die) = @_; return sub { my ($rolls) = @_; return map { $die->() } (1 .. $rolls); } }
- 46. my $dice_tower = $dice_tower_generator->($d6); say join(', ', $dice_tower->(20));
- 47. use List::Util; say sum $dice_tower->(20);
- 48. use List::Util; say reduce {$a + $b} $dice_tower->(20);
- 49. So why not use this stuff for everything?
- 50. The compilers not out to help you
- 51. Declaring functions gets obtuse after awhile
- 52. Purity isn't an option, everything changes
- 53. The community loves objects
- 54. If it was simple in a functional language it probably takes some hacking to make it work in perl
- 55. And the language isn't extensible, yet
- 56. Good things are to come
- 57. Perl 6
- 58. Static typing Better syntax Blocks and closures List comprehension Automatic parallelisation Lots more