Functional Design Patterns.pdf

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1、FunctionalDesignPatterns@ScottWlaschinfsharpforfunandprofit.comFunctionalDesignPatternsX@ScottWlaschinfsharpforfunandprofit.comFunctionalDesignPatterns@ScottWlaschinfsharpforfunandprofit.comFunctionalpatterns•Apomorphisms•Dynamorphisms•Chronomorphisms•Zygohi

2、stomorphicprepromorphismsFunctionalpatterns•CorePrinciplesofFPdesign–Functions,types,composition•Functionsasparameters–Abstraction,Dependencyinjection–Partialapplication,Continuations,Folds,•Chainingfunctions–Errorhandling,Async–Monads•Dealingwithwrappeddata

3、–Lifting,Functors–ValidationwithApplicatives•Aggregatingdataandoperations–MonoidsThistalkFunctionalprogrammingisscaryFunctionalprogrammingisscaryObjectorientedprogrammingisscaryOOpattern/principleFPpattern/principle•SingleResponsibilityPrinciple•Functions•Op

4、en/Closedprinciple•Functions•DependencyInversion•Functions,alsoPrinciple•InterfaceSegregation•FunctionsPrinciple•Factorypattern•Yes,functions•Strategypattern•Ohmy,functionsagain!•Decoratorpattern•Functions•Visitorpattern•FunctionsSeriously,FPpatternsarediff

5、erentAshortandmostlywronghistoryofprogrammingparadigmsObject-Orientedprogramming•Whatweenvisioned:–Smalltalk•Whatwegot:–C++“Worseisbetter”–ObjectorientedCobol–PHP–JavaFunctionalprogramming•Whatweenvisioned:–Haskell,OCaml,F#,etc•Whatwegot:–??Pleasedon’tletthi

6、shappentoFP!Importanttounderstand!COREPRINCIPLESOFFPDESIGNCoreprinciplesofFPdesignStealfrommathematicsTypesarenotclassesFunctionsarethingsFunctionCompositioneverywhereCoreprinciple:Stealfrommathematics“Programmingisoneofthemostdifficultbranchesofappliedmathe

7、matics”-E.W.DijkstraWhymathematicsDijkstrasaid:•Mathematicalassertionstendtobeunusuallyprecise.•Mathematicalassertionstendtobegeneral.Theyareapplicabletoalarge(ofteninfinite)classofinstances.•Mathematicsembodiesadisciplineofreasoningallowingassertionstobemad

8、ewithanunusuallyhighconfidencelevel.“Object-orientedprogrammingisanexceptionallybadideawhichcouldonlyhaveoriginatedinCalifornia.”E.W.DijkstraMathematicalfunctionsDomain(int)Codomain(int)……-10011