Observations

lists in Lambda in JavaScript

2024-01-01T00:12:30Z

(disclaimer: this is educational material)

  // Definitions for Boolean Logic
  const True  = x => y => x
  const False = x => y => y
  const Bool = b => b ? True : False

  // Definitions for pair and projection
  const p1 = x => y => x // did you notice? It's True
  const p2 = x => y => y // did you notice? It's False
  const Pair = x => y => f => f(x)(y)

  // Option constructors
  const None = Pair(True)("None")
  const Some = x => Pair(False)(x)

  // List constructors and operations
  const Nil = Pair(True)("Nil")
  const isEmpty = x => x(p1)
  const Head = z => z(p2)(p1)
  const HeadOption = z => z(p1)(None)(Some(z(p2)(p1)))
  const Tail = z => z(p2)(p2)
 
  const Cons = h => t => Pair(False)(Pair(h)(t))
  const Map = z => f => (isEmpty(z) (() => Nil) (() => Cons(f(Head(z))) (Map(Tail(z))(f))))()

  // visualizer

  const show = text => xs => {
    var buf = ""
    Map(xs)(x => buf += (x + ":"))
    println(`${text} ${buf}Nil`)
  }

  const Filter  = z => p =>
     (isEmpty(z) 
       (() => Nil) 
       (() => (p(Head(z)) (Cons(Head(z))(Filter(Tail(z))(p))) (Filter(Tail(z))(p))))
      )() // have to do it lazily

  // samples
  const ab = Cons("a")(Cons("b")(Nil))

  show("Expecting Nil ->")(Nil)
  show("Expecting a:b:Nil ->")(ab)

  const list1 = Cons(1)(Cons(-2)(Cons(3)(Cons(-4)(Nil))))

  show("three numbers")(list1)
  const isPositive = x => Bool(x > 0)

  show("squares")(Map(list1)(x => x*x))
  show("positives")(Filter(list1)(isPositive))

comments

Option in JavaScript, funny lambda style

2023-12-30T23:23:23Z

// Definitions for Boolean Logic
const True = x => y => x
const False = x => y => y
const Bool = b => b ? True : False

// Definitions for pair and projection
const p1 = x => y => x // did you notice? It's True
const p2 = x => y => y // did you notice? It's False
const Pair = x => y => f => f(x)(y)

// Option constructors and operations
const None = Pair(True)("None")
const Some = x => Pair(False)(x)
const isEmpty = x => x(p1)
const FlatMap = x => f => isEmpty(x) (None) ( f(x(p2)))
const Map = x => f => isEmpty(x) (None) (Some(f(x(p2))))
const Filter = x => p => isEmpty(x) (None) (p(x(p2)) (x) (None))

// visualizer
const show = text => xOpt => {
Map(xOpt)(x => println(text + x))
}

// samples
show("Expecting Some ")(Some(42))
show("Expecting None ")(None)

const isPositive = x => Bool(x > 0)
show("0 positive? ")(Filter(Some(0))(isPositive))
show("2 positive? ")(Filter(Some(2))(isPositive))

const dec = n => n > 10 ? Some(n-10) : None

show("expecting None from None: ")(FlatMap( None)(dec))
show("expecting None from 5: ") (FlatMap(Some(5) )(dec))
show("expecting 32 from 42: ") (FlatMap(Some(42))(dec))

comments

inside javascript engine

2022-02-07T12:51:24Z

https://blog.devgenius.io/inside-the-javascript-engine-bb7b9f26e84b

A brief explanation of the JavaScript Engine

comments

с изумлением обнаружил у себя в коде

2021-03-15T03:36:25Z


const option = x => 
  typeof x === 'undefined' ? None : Some(x)

const None = {
  map: f => None,
  flatMap: f => None,
  toString: () => 'None'
}

const Some = x => ({
  flatMap: (f => f(x)),
  map: (f => option(f(x))),
  toString: () => `Some(${x})`
})

comments

my presentation today

2020-11-13T01:43:28Z

https://observablehq.com/@vpatryshev/finger-trees-in-js

comments

the code I teach now

2020-05-29T22:05:40Z

const iterate = f => z => pair(z, () => iterate(f)(f(z)));

const integers = iterate(n => n+1)(0);

comments

the book I just needed

2019-12-19T15:41:05Z

https://sicp.comp.nus.edu.sg/

comments

JS -> Go -> Rust

2019-09-19T05:41:41Z

https://www.quora.com/Why-did-Ryan-Dahl-give-up-upon-Node-js-for-Go

comments

progress

2018-09-02T23:33:26Z

https://github.com/yishn/tikzcd-editor

comments

140 chars of javascript

2018-01-02T15:55:58Z

here - beautiful images!

comments

кстати о языцех

2017-05-21T04:05:19Z

Джавасприпт, Хаскель и Скала, и, говорят, OCaml, из-за своей компактности, канают в качестве скриптовых языков.

Питон в этом смысле тоже ничо, но там, во-первых, споткнуться можно много где, во-вторых, на уровне компиляции нам ничего не скажут. Это уже на продакшене ебанется. То-то квора, которая на питоне, деплоится по сто раз в час (а тесты потом гоняют, и кодревью тоже).

comments