Functional Programming Language OCaml Tutorial 科大 - 耶鲁联合研究中心

Outline  Introduction  Get Started  OCaml Basis  Basic Concepts  Examples  Discussion

Introduction Functional programming(FP) emphasizes application of functions and has its roots in lambda calculus The difference between function in FP and imperative languages is side effects FP can also be accomplished in imperative languages.

History 1950s LISP 1960s APL -> J -> K 1970s ML -> Objective Caml, Standard ML 1980s Dependent Types -> Coq, Agda, Epigram 1987 Haskell

Get Started Install win-msvc.exe win-msvc.exe Interactive Run “ocaml” Objective Caml version # 1+2;; - : int =3 Use any text editor Emacs/Vim Notepad++ …

Get Started Run Emacs Visist New File -> “test.ml” Short Keys C-c C-s “start ocaml” C-c C-b “eval whole file” C-c C-r “eval selected code” Tab “Ident” Demo

OCaml Declaring Variables Variables in OCaml are immutable! Declaring Functions OCaml functions don’t have explicit “return”. The return value is the last statement.

OCaml All functions and values in OCaml have a datatype let add x y = (x + y);; OCaml will report val add : int -> int -> int = which means function “add” takes two “int” inputs and return a “int” Generic Function let fst x y = x - val fst : 'a -> 'b -> 'a = # fst 1 2 ;; # fst "a" "b";; # fst "a" 1;;

Recursion and Nested Function

Pattern Match Example Patterns can be chained together

High-order Functions A high-order function is a functions that takes another function as a parameter or a function returns another function or both. Function can be partial applied add : int -> int -> int add 1 : int -> int add 1 2 : int let f = add 1 let result = f 2

High-order Functions Composition let double x = x * 2 let power x = x * x let compose f g x = g (f x) let result = (compose double power) 4 Pipeline let pipe x f = f x let result = (pipe (pipe 4 double) power)

Anonymous Function Example fun x -> x * 2 We can rewrite examples from Page 11 compose (fun x->x*2) (fun x->x*x) 4 Much use of anonymous functions

Data Structures Option Type Tuples List

Examples Fibonacci number List filter, map, fold

Lab Write a calculator Provided parser combinators built-in parsers integer, alpha, ident, char, string combinators many, sepBy, paren, chainl infix >> >>= #use “parsec.ml”;;

Lab Grammar Exp :: Term [+-] Term Term :: Factor [*/] Factor Factor :: int | ( Exp ) Get Start let add = (char ‘+’) >> (return (+)) “+” Receive a char ‘+’ and return function (+) with possible error message “+” let factor = (paren exp) (integer “integer”) either a parened “exp” or an integer let term = chainl factor (mul div) a list of factor chained with “mul” or “div” let expr = chainl term (add sub)

Lab Write a parser for first-order logic formula Formula :: Clause \/ Clause Clause :: Term /\ Term Term :: Literal | Literal Comp Literal Literal :: id | int | bool Eval the formula with given environment (x:true;y:false;….)

TODO Spec# ESC/Java Compcert CComp