Haskell, the most pragmatic functional language

Transcript

1. Haskell Pragmatic Functional Programming
2. Nope, we’re busy Not pragmatic dude… Programs
 Complexity
3. “Haskell is the most pragmatic functional programming language”
4. Functional Programming A. Functions (the real ones, aka pure ones) B. Functions as values (higher-order) C. Recursion (the only loop construction)
5. Functional Language A. Support for functional abstractions B. Support for handling side-effects C. Efficient (you don’t pay the abstraction)
6. Abstraction Side-Effects Efficiency Scala Erlang Haskell
7. Abstraction
8. Abstraction 
 Side Effects
9. Abstraction 
 Side Effects Efficiency
10. –Gabriel González “Haskell has effects. The difference is that they’re first- class values and not to-the-side”
11. How on Earth is Haskell not popular?
12. Iron Triangle concise
 fast to write efficient
 (fast to run) easy
 (fast to learn)
13. Recursion
14. • Is more general • Haskell tail recursive functions in constant time • Haskell mutual recursive functions in constant time (Monads!)
15. New types
16. New Types • Wrapper evaporates after compilation newtype PK = PrimaryKey Int
17. Laziness
18. Laziness • Possible to reuse functions foldr = … map = foldr… filter = foldr …
19. Type inference
20. Type inference • Global type inference
23. Deferred type errors/Type holes
24. Deferred types • -fdefer-type-errors Type errors are converted to runtime errors (good for ghci sessions) • Type holes put the compiler to work for us main = _
25. Dynamic types
26. Dynamic types
27. Software transactional memory
28. STM Haskell is the best language in the world in which to implement an STM • It was originally 100 lines of code, and even now it’s only about 600 lines of C! • It exploits three properties of the language: purity, immutability and laziness • Haskell retries an STM transaction as needed. Immutability allows it to do this fearlessly, and laziness avoids fully evaluating the transaction • STM is harder in other languages. For instance in Clojure you have to manually implement rollback functionality. https://begriffs.com/posts/2016-04-02-software-transactional-memory.html
30. Higher-kinded types
31. Higher-kinded types class Monad (m :: * -> *) where
32. Polymorphic! Higher-kinded types
33. Polymorphic! Higher-kinded types data T (a :: k) = …
34. Data types type classes (type families)
35. Data types type classes (type families) data family XList a data instance XList Char = XCons Char (XList Char) | XNil data instance XList () = XListUnit Int
36. Much more • Loops fusion • Dependent types • Functional Reactive Programming • Speed!
39. Use Haskell!!!
40. return $