List - XP Days

Objektorientierte und funktionale Softwareentwicklung
Refactoring von Java Legacy Code
Clean Code und Software Craftsmanship
Specification by Example und
Domain-Driven Design
Facilitation von Code Retreats und
Legacy Code Retreats
Michael Sperber
• funktionale Programmierung
• Scala, Clojure, F#, Haskell, OCaml, Erlang, Elixir, Swift
• Schulungen und Coaching
• Blog: funktionale-programmierung.de
• Entwickerkonferenz BOB bobkonf.de
"IoT Goes Nuclear:
Creating a ZigBee Chain Reaction"
http://iotworm.eyalro.net/
https://www.arbornetworks.com/blog/asert/mirai-iot-botnet-description-ddos-attack-mitigation/
http://heartbleed.com/
https://www.wired.com/2015/07/hackers-remotely-kill-jeep-highway/
http://wp.doc.ic.ac.uk/riapav/wp-content/uploads/sites/28/2014/05/HACMS-Fisher.pdf
User Stories
"We will do what is needed and asked for, but no more."
FIXME
http://www.extremeprogramming.org/values.html
Korrekte Software – wie?
Intel Pentium, FDIV-Bug
Listen
data List: (a:Type) -> Type where
Nil : List a
(::) : a -> List a -> List a
Listen
mapL : (a -> b) -> List a -> List b
mapL f [] = []
mapL f (x :: xs) = f x :: mapL f xs
Nicht-Termination
x : a
x = x
Vektoren
data Vect : (n:Nat) -> (a:Type) -> Type where
Nil: Vect 0 a
(::) : a -> Vect n a -> Vect (n+1) a
Automatische Herleitung Implementierung
mapV : (a-> b) -> Vect n a -> Vect n b
mapV f [] = []
mapV f (x :: xs) = f x :: mapV f xs
Element-Test herleiten?
isElemF : a -> Vect n a -> Bool
isElemF x [] = False
isElemF x (y :: xs) = False
Beweis als Objekt
data Position : a -> Vect n a -> Type where
Head : Position x (x::xs)
Tail : Position x xs -> Position x (y::xs)
Beispiele
oneInVector : Position 1 [1, 2, 3]
oneInVector = Head
twoInVector : Position 2 [1, 2, 3]
twoInVector = Tail Head
-- fourInVector : Position 4 [1, 2, 3]
-- fourInVector = Tail (Tail (Tail ?fourInVector_rhs1))
Elemente gleich?
data Equals : a -> a -> Type where
Same : Equals x x
maybeEq : (x : a) -> (y: a) -> Maybe (Equals x y)
data Maybe : a -> Type where
Nothing : Maybe a
Just : a -> Maybe a
Element-Test mit Beweis
isElem : Eq a =>
(x : a) -> (xs : Vect n a) -> Maybe (Position x xs)
isElem x [] = Nothing
isElem x (y :: xs) = case maybeEq x y of
Nothing => (case isElem x xs of
Nothing => Nothing
(Just pos) => Just (Tail pos))
(Just Same) => Just Head
http://projects.laas.fr/IFSE/FMF/J3/slides/P05_Jean_Souyiris.pdf
https://sel4.systems/
http://www.russinoff.com/papers/paris.ps
Dokumentation
Spezifikation
Typen
Verifikation
Generierung
Tools
• Coq
• Isabelle
• Agda
• Idris
• ATS
• F*
• ACL2
• Liquid/Dependent Haskell
Auf dem Weg ...
http://flint.cs.yale.edu/certikos/
Code vs. Dokumentation
"A program, written without requirements and specifications,
can never be incorrect - it can only be surprising."
Young, Boebeit, and Kainin: "Proving a Computer System Secure",
The Scientific Honeyweller, Vol. 6, Nr. 2 (Juli 1985)