Project Tools: Ocaml and Javascript (Pre Lecture)

Project Tools: OCaml and JavaScript (Pre Lecture)

Dr. Neil T. Dantam

CSCI-400, Colorado School of Mines

Spring 2021

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 1/23 OCaml Lineage

Lisp ML OCaml ◮ Functional ◮ Still Functional ML + some object stuﬀ ◮ Code-is-data ◮ Less metaprogramming metaprogramming ◮ Now Statically typed ◮ Dynamically Typed

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 2/23 JavaScript c. 1995 at Netscape Communications (paraphrased)

The web must be dynamic!

Let’s put Scheme JavaScript Features in Netscape! ◮ Semantics: ◮ Largely Lisp-like: Uhh... Functional, Dynamic ◮ Just make them Some warts/weirdness think it’s Java. ◮ Syntax: C/Java-like Marc Andreeson

Brendan Eich Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 3/23 Installation

OCaml OCaml sudo apt-get install ocaml sudo apt-get install nodejs

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 4/23 Running the interpreter

OCaml JavaScript % ocaml % node # or sometimes nodejs # print string "Hello, World!" ;; > console.log("Hello, World!")

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 5/23 Emacs Tip: OCaml and JS Interpreters

OCaml JavaScript ;; Tuareg ;; js-comint M-x run-ocaml M-x js-comint-repl

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 6/23 OCaml / JS Rosetta Outline

OCaml / JS Rosetta

More OCaml

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 7/23 OCaml / JS Rosetta Function Deﬁnition

Pseudocode λa . 1+ a

OCaml JavaScript

function a −> 1+ a ( function ( a ) { return 1 + a ; } )

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 8/23 OCaml / JS Rosetta Function Application

Pseudocode (λa . 1+ a) 2

JavaScript OCaml ( function ( a ) { ( function a −> 1 + a ) 2 return 1 + a ; }) (3)

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 9/23 OCaml / JS Rosetta Conditional

Pseudocode if true then 1 else 2

JavaScript (expression)

true ? 1 : 2 OCaml

if true then 1 else 2 JavaScript (statement)

if ( true ) { console . l o g (1) } else { console . l o g (2) }

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 10/23 OCaml / JS Rosetta Local Variables

Pseudocode let a ← 2 in 1+ a

JavaScript (var)

var a = 2; console . l o g (1+a ); OCaml

let a = 2 in 1+ a JavaScript (let)

let a = 2; console . l o g (1+a );

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 11/23 OCaml / JS Rosetta JavaScript var vs. let

Var: Function Scope Let: Block Scope

( function () { ( function () { var a = 1; let a = 1; // 1st a { { var a = 2; // same a let a = 2; // 2nd a } } return a ; return a ; // 1st a }) (); }) (); // => 2 // => 1

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 12/23 OCaml / JS Rosetta Global Functions

Pseudocode defun addone (a) → 1+ a;

JavaScript (expression) OCaml function addone ( a ) { let addone a = 1+a return 1+a ; }

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 13/23 OCaml / JS Rosetta OCaml: Recursive Functions

Pseudocode OCaml

Function fact(n) let rec fact n = 1 if n = 0 then 1 if n = 0 then 1 2 else n ∗ fact(n − 1) else n ∗ fact (n−1)

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 14/23 OCaml / JS Rosetta Lists

Pseudocode

cons (1, cons (1, NIL))

OCaml (cons)

1::2::[] JavaScript (Array)

[1 ,2] OCaml (list)

[1; 2]

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 15/23 OCaml / JS Rosetta Higher-Order Functions Passing a function

Pseudocode (λf . f 2) (λa . 1+ a)

JavaScript

OCaml ( function ( f ) { return f (2); ( function f −> f 2) }) ( function ( a ) { ( function a −> 1 + a) return 1+a ; })

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 16/23 OCaml / JS Rosetta Higher-Order Functions Returning a function

Pseudocode λb . (λa . a + b)

JavaScript

OCaml ( function ( b ) { return function ( a ) { function b −> a + b ; function a −> a +b } })

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 17/23 More OCaml Outline

OCaml / JS Rosetta

More OCaml

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 18/23 More OCaml Pattern Matching Factorial

Pseudocode OCaml

Function fact(n) let rec fact n = 1 match n with match n with 2 case 0 → 1 0 −> 1 3 otherwise n ∗ fact(n − 1) | −> n ∗ fact (n−1)

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 19/23 More OCaml Pattern Matching List Copy

Pseudocode OCaml Function cpy(ℓ) 1 match ℓ with let rec cpy ell = 2 case NIL → NIL match ell with 3 case cons(a, d) → [] −> [] 4 cons(a, cpy(d)) | a::d −> a :: cpy d

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 20/23 More OCaml Unit Type

Return Type Parameter Type

let myprint s = let hello () = print string (s : string) print s t r i n g ”Hello!\ n”

(∗ myprint : string −> unit ∗) (∗ hello : unit −> unit ∗)

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 21/23 More OCaml OCaml Precedence Precedence Operator Associativity 0preﬁx-symbol – 1 ..(.[.{ – 2 #... left 3 func. app., constr. app., tag app., assert, lazy left 4 --. (preﬁx) – 5 **...lsllsrasr right 6 *.../...%...modlandlorlxor left 7 +... -... left 8 :: right 9 @... ˆ... right 10 =... <... >... |...&...$...!= left 11 &&& right 12 or || right 13 , – 14 <- := right 15 if – 16 ; right 17 let match fun function try – OCaml Manual

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 22/23 More OCaml References (you will need to read them)

OCaml Tutorial https://ocaml.org/learn/tutorials/ OCaml Reference https://ocaml.org/releases/4.11/htmlman/index.html JavaScript Spec https://www.ecma-international.org/ecma-262/10.0/index.html MDN https://developer.mozilla.org/en-US/docs/Web/JavaScript

Dantam (Mines CSCI-400) OCaml, JavaScript (Pre Lecture) Spring 2021 23/23