A brief introduction to functional programming

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In this short presentation we explain some of the general concepts of functional programming.

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A brief introduction to functional programming

  1. 1. A brief introduction to functional programming Sebastian Wild Stylight GmbH October 31, 2012
  2. 2. Functional programming languagesSome programming concepts Variables and Functions Currying Functions as parameters AccumulatorsAdvanced examplesSummary
  3. 3. And that language is fast. I mean, really astoundingly fast, which is why it is so evil. It’s like that psychotic girlfriend that was amazing in bed. You keep trying to break up with her, but she seduces you right back into that abusive relationship.from brool.comArticle: The Genius of Python, The Agony of OCaml
  4. 4. Functional programming languages Pure Haskell, Charity, Clean, Curry, Hope, Miranda Impure Erlang, F#, Lisp, ML (Standard ML, OCaml), Scala, Spreadsheets
  5. 5. First program # p r i n t s t r i n g ” H e l l o , World ! ” ; ; H e l l o , World : u n i t = ( )
  6. 6. Variables and Functions # let a = 5;; val a : int = 5 # let a = 5 + 3;; val a : int = 8 (∗ ! ! A t t e n t i o n ! ! Strong type system ∗) # let a = 5 + 3.0;;
  7. 7. Variables and Functions # l e t a = (5 , () , ” Hello ” ) ; ; v a l a : i n t ∗ u n i t ∗ s t r i n g = (5 , ( ) , ” H e l l o ”) # let f x = x ∗ x ;; v a l f : i n t −> i n t = <fun>
  8. 8. Currying # let f (x , y) = x ∗ y ; ; v a l f : i n t ∗ i n t −> i n t = <fun>
  9. 9. Currying # let f x y = x ∗ y ;; v a l f : i n t −> i n t −> i n t = <fun> ( ∗ Types a r e r i g h t b r a c k e t e d ∗ ) i n t −> ( i n t −> i n t )
  10. 10. Currying # let f x y = x ∗ y ;; # let a = f 5;; v a l a : i n t −> i n t = <fun> # let b = a 6;; v a l b : i n t = 30 (∗ Function c a l l s are l e f t b r a c k e t e d ∗) # v a l b = ( f 5) 6 ; ; v a l b : i n t = 30
  11. 11. Functions as parameters # let a = [1;2;3;4];; val a : int l i s t = [ 1 ; 2; 3; 4] # l e t r e c map f s = match s w i t h [ ] −> [ ] | x : : x s −> ( f x ) : : ( map f x s ) ; ; v a l map : ( ’ a −> ’ b ) −> ’ a l i s t −> ’ b l i s t = <fun> # l e t b = map ( f u n v −> 2 ∗ v ) a ; ; val b : int l i s t = [ 2 ; 4; 6; 8]
  12. 12. Functions as parameters L i s t . f o l d l e f t : ( ’ a −> ’ b −> ’ a ) −> ’ a −> ’ b l i s t − L i s t . f o l d l e f t f a [ b1 ; . . . ; bn ] f ( . . . ( f ( f a b1 ) b2 ) . . . ) # L i s t . f o l d l e f t (+) 0 [ 1 ; 2 ; 3 ; 4 ; 5 ; 6 ] ; ; − : i n t = 21
  13. 13. Accumulators Faculty of n: # l e t rec fac n = i f n <= 0 t h e n 1 else n ∗ fac (n − 1 ) ; ; v a l f a c : i n t −> i n t = <fun>
  14. 14. Accumulator Tail recursive: # l e t fac n = l e t r e c fac ’ acc n = i f n <= 0 t h e n a c c e l s e f a c ’ ( n∗ a c c ) ( n−1) i n fac ’ 1 n ; ; v a l f a c : i n t −> i n t = <fun>
  15. 15. Advanced examples http://www.ffconsultancy.com/ocaml/bunny/index.html http://www.ffconsultancy.com/ocaml/ray tracer/index.html
  16. 16. Summary No side effects Strong type system Mathematical functions can be expressed very easily Steep learning curve https://github.com/wildsebastian/AlgorithmsDataStructures

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