Fn.py: ideas & internals

Fn.py library (https://github.com/kachayev/fn.py): key ideas and internal implementation details for functional programmers

Transcript

1. Fn.py ideas and internals Wednesday, March 27, 13
2. Fn.py https://github.com/kachayev/fn.py Wednesday, March 27, 13
3. About me • Alexey Kachayev • CTO at KitApps Inc. • Open source activist • Functional programming advocate • Erlang, Python, Scala, Clojure, Go, Haskell • @kachayev • github.com/kachayev • kachayev at gmail.com Wednesday, March 27, 13
4. About Python • minimalistic syntax • dynamically typed • imperative (by design) • “multi paradigm” • functions are variables • lambdas • iterators, generators, decorators, ... • mutable data types (mostly) Wednesday, March 27, 13
5. About Fn.py • enjoy FP in Python • developed on my own talks materials • not only proof of concept • tremendous support from community Wednesday, March 27, 13
6. Overview • Scala-style lambdas • Stream and infinite sequences declaration • TCO / trampolines • Itertools recipes • Option monad • Python 2/3 unification for functional stuff Wednesday, March 27, 13
7. Scala-style lambdas Wednesday, March 27, 13
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9. Scala-style lambdas Wednesday, March 27, 13
10. Scala-style lambdas Wednesday, March 27, 13
11. Why? • Code readability • Improve you vision • Keyboard will work longer Wednesday, March 27, 13
12. How? • _Callable class • shortcut instance • overloaded operators • each instance - unary or double-side operations tree Wednesday, March 27, 13
13. Streams and infinite sequences Wednesday, March 27, 13
14. What? • Lazy evaluated list • Composable producers • Any number of consumers • All consumers share one iterable origin • Infinite (potentially) sequence Wednesday, March 27, 13
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16. So what? Wednesday, March 27, 13
17. Haskell Wednesday, March 27, 13
18. Clojure Wednesday, March 27, 13
19. Scala Wednesday, March 27, 13
20. Python Wednesday, March 27, 13
21. Tail call optimization “I don't believe in recursion as the basis of all programming. This is a fundamental belief of certain computer scientists, especially those who love Scheme and like to teach programming by starting with a "cons" cell and recursion.” Guido van Rossum Wednesday, March 27, 13
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23. Okay.... Wednesday, March 27, 13
24. Trampolines unwrap tail calls to while loop Wednesday, March 27, 13
25. Recursion = Induction recursion = induction basis + step while loop = induction basis + step Wednesday, March 27, 13
26. Trampoline Wednesday, March 27, 13
27. Control flow patterns Wednesday, March 27, 13
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29. Scala-style Option Wednesday, March 27, 13
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32. What? • analog = list with 1 or 0 elements • functor + fmap • monadic flatMap operation • “retry” computations Wednesday, March 27, 13
33. When? • computations that may fail • heavy execution branching (if/else/try/etc) Wednesday, March 27, 13
34. Where to find more? https://github.com/kachayev/fn.py Wednesday, March 27, 13
35. Questions? http://kachayev.github.com/talks Wednesday, March 27, 13