计算机科学分类程序设计语言functional-_7.pptxVIP

Programming LanguagesDan Grossman Optional: Why Functional Languages? Functional Programming Why spend 60-80% of course using functional languages: Mutation is discouraged Higher-order functions are very convenient One-of types via constructs like datatypes Because: These features are invaluable for correct, elegant, efficient software (great way to think about computation) Functional languages have always been ahead of their time Functional languages well-suited to where computing is going Most of course is on (1), so a few minutes on (2) and (3) … 2 Dan Grossman, Programming Languages Ahead of their time All these were dismissed as “beautiful, worthless, slow things PL professors make you learn” Garbage collection (Java didn’t exist in 1995, PL courses did) Generics (ListT in Java, C#), much more like SML than C++ XML for universal data representation (like Racket/Scheme/LISP/…) Higher-order functions (Ruby, Javascript, C#, …) Type inference (C#, Scala, …) Recursion (a big fight in 1960 about this – I’m told ) … 3 Dan Grossman, Programming Languages The future may resemble the past Somehow nobody notices we are right… 20 years later “To conquer” versus “to assimilate” Societal progress takes time and muddles “taking credit” Maybe pattern-matching, currying, hygienic macros, etc. will be next 4 Dan Grossman, Programming Languages Recent-ish Surge, Part 1 Other popular functional PLs (alphabetized, pardon omissions) Clojure Erlang F# Haskell OCaml Scala Some “industry users” lists (surely more exist): /haskellwiki/Haskell_in_industry /companies.html In general, see 5 Dan Grossman, Programming Languages Recent-ish Surge, Part 2 Popular adoption of concepts: C#, LINQ (closures, type inference, …) Java 8 (closures) MapReduce / Hadoop Avoiding side-effects essential for fault-toleranc