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nth[2]? nth[1]?](https://image.slidesharecdn.com/ciaovsciao-110909190822-phpapp01/85/Functional-Pe-a-rls-the-Purely-Functional-Datastructures-edition-30-320.jpg)
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nth[2]? nth[0]!](https://image.slidesharecdn.com/ciaovsciao-110909190822-phpapp01/85/Functional-Pe-a-rls-the-Purely-Functional-Datastructures-edition-31-320.jpg)
Functional Pe(a)rls - the Purely Functional Datastructures edition
- 1. Functional Pe(a)rls osfameron @ IPW2011, Turin the “purely functional data structures” edition http://www.fickr.com/photos/jef_saf/3493852795/
- 2. previously on Functional Pe(a)rls... (IPW, LPW, YAPC::EU, nwe.pm) currying operator references: op(+) Acme::Monads Devel::Declare
- 3. C I A O vs. C I A O
- 4. 0 1 2 3 C I A O
- 5. 0 1 2 3 C I A O 0th element
- 6. 0 1 2 3 M I A O 0th element
- 7. 0 1 2 3 M I A O 0th element no kittens were harmed during the making of this presentation
- 8. 0 1 2 3 M I A O 2nd element
- 9. 0 1 2 3 M I A O 4th element
- 10. 0 1 2 3 M I A O max: 3
- 11. 0 1 2 3 M I A O max: 3
- 12. 0 1 2 3 4 M I A O W max: 4 4th element
- 13. max: 3 0 1 2 3 100,000 M I A O …
- 14. 0 1 2 3 M I A O max: 3
- 15. 0 1 2 3 4 M I A O W max: 4 0 1 2 3 4 5 M I A O W ! max: 5
- 16. 0 1 2 3 4 M I A O W max: 4 0 1 2 3 4 5 M I A O W ! max: 5
- 17. Arrays C I A O vs. C I A O
- 18. Perl @arrays C I A O “dynamic array” vs. C I A O
- 19. C I A O
- 20. C I A O
- 21. C I A O Head
- 22. C I A O Tail
- 23. C I A O
- 24. C I A O
- 25. I A O
- 26. A O
- 27. O
- 28. C I A O 0th
- 29. C I A O nth - 1
- 30. C I A O nth[2]? nth[1]?
- 31. C I A O nth[2]? nth[0]!
- 32. C I A O ?
- 33. ● C I tail “ciao” → “iao” A O ?
- 34. ● C I tail “ciao” → “iao” A O ? ● tail “iao” → “ao” ● tail “ao” → “o” ● tail “o” → ?
- 35. ● C I tail “ciao” → “iao” A O ? ● tail “iao” → “ao” ● tail “ao” → “o” ● tail “o” → “” (the empty string)
- 36. C I A O
- 37. List = Head Tail (another List) or...
- 38. Here comes the science^wPerl!
- 39. Moose(X::Declare) use MooseX::Declare; BEGIN { role_type 'List' } role List { requires 'head'; requires 'tail'; }
- 40. List::Link class List::Link with List { has head => ( is => 'ro', isa => 'Any' ); has tail => ( is => 'ro', isa => 'List' ), }
- 41. List::Link class List::Link with List { has head => ( is => 'ro', isa => 'Any' ); has tail => ( is => 'ro', isa => 'List' ), }
- 42. List::Link class List::Link with List { has head => ( is => 'ro', isa => 'Any' ); has tail => ( is => 'ro', isa => 'List' ), }
- 43. List::Empty class List::Empty with List { method head { die "Can't take head of empty list!" } method tail { die "Can't take tail of empty list!" } }
- 44. So we can write: my $list = List::Link->new( head => 'c', tail => List::Link->new( head => 'i', tail => List::Link->new(...
- 45. Sugar! my $list = List->fromArray( qw/ c i a o /);
- 46. Multimethods use MooseX::MultiMethods; multi method fromArray ($class:) { return List::Empty->new; }
- 47. Multimethods use MooseX::MultiMethods; multi method fromArray ($class:) { return List::Empty->new; }
- 48. Multimethods multi method fromArray ($class: $head, @tail) { return List::Link->new( head => $head, tail => $class->fromArray(@tail), ); }
- 49. Eeek! Recursion! my $list = List::fromArray(1..1000000);
- 50. Eeek! Recursion! my $list = List::fromArray(1..1000000); Deep recursion on subroutine "List::fromArray" at foo.pl line 20
- 51. Eeek! Recursion! multi method fromArray ($class: $head, @tail) { return List::Link->new( head => $head, tail => $class->fromArray(@tail), ); }
- 53. Eeek! Recursion! fromArray List::Link->new (..., fromArray)
- 54. Eeek! Recursion! fromArray List::Link->new (..., fromArray) List::Link->new (..., fromArray)
- 55. Eeek! Recursion! fromArray List::Link->new (..., fromArray) List::Link->new (..., fromArray) List::Link->new (..., fromArray)
- 56. Eeek! Recursion! fromArray List::Link->new (..., fromArray) List::Link->new (..., fromArray) List::Link->new (..., fromArray) List::Link->new (..., fromArray)
- 57. Eeek! Recursion! fromArray List::Link->new (..., fromArray) List::Link->new (..., fromArray) List::Link->new (..., fromArray) List::Link->new (..., fromArray) = $list
- 58. Eeek! Recursion! fromArray List::Link->new (..., fromArray) List::Link->new (..., fromArray) List::Link->new (..., fromArray) = $list
- 59. Eeek! Recursion! fromArray List::Link->new (..., fromArray) List::Link->new (..., fromArray) = $list
- 60. Eeek! Recursion! fromArray List::Link->new (..., fromArray) = $list
- 61. Eeek! Recursion! fromArray = $list
- 62. Eeek! Recursion! no warnings 'recursion'; $DB::deep = 100_000_000;
- 63. Eeek! Recursion! no warnings 'recursion'; $DB::deep = 100_000_000; Papering over the cracks
- 64. Tail Call Elimination Sub::Call::Tail Sub::Call::Recur by nothingmuch
- 66. Tail call elimination List::Link->new (..., fromArray)
- 67. Tail call elimination List::Link->new (..., fromArray)
- 68. Tail call elimination List::Link->new (..., fromArray)
- 69. Tail call elimination List::Link->new (..., fromArray)
- 70. Tail call elimination List::Link->new (..., fromArray) = $list
- 71. Tail Call Elimination use Sub::Import 'Sub::Call::Tail' tail => { -as => 'tail_call' }; multi method fromArray ($self: $head, @tail) { tail_call List::Link->new( head => $head, tail => $self->fromArray(@tail), ); }
- 72. Indexing into List multi method nth (List::Empty $self: Int $pos) { die "Can't index into an Empty list"; }
- 73. Indexing into List multi method nth (Int $pos where { $_ == 0 }) { return $self->head; }
- 74. Indexing into List multi method nth (Int $pos where { $_ > 0 }) { tail_call $self->tail->nth( $pos - 1 ); }
- 75. C I A O M
- 76. C I A O M W
- 77. C I A O M W Mutation leads to bugs (and misspellings!)
- 78. C I A O M I A O W
- 79. C I A O C I B
- 80. C I A O C I B Copy everything upstream of a change Downstream of changes can be shared
- 81. C I A O C I B O Doubly linked lists have no downstream!
- 82. pure-fp-book ● https://github.com/osfameron/pure-fp-book ● Purely Functional Data Structures for the... ● Impure ● Perl Programmer ● Working Programmer ● Mutable, Rank-Scented Many