Intro to Elm

What is it?

Alternative to JS
Pure, static, strict functional language
Hindley-Milner type inference (like Haskell, OCaml, Rust, F# etc)
Very unlike implicit subtyping of e.g. Typescript
Prescribed architecture and comprehensive standard lib
Motivations? Errors , stability, predictability

How does it work?

State

View

Update

init

Events

i.e. very much like a certain flavour of React

Demo

1 + 1 = 2

1 + 1 = 2

2 * 2 = 4

1 + 4 = 5

Cardinality

String test = null;

//vs 

test = Nothing

C#: null inhabits every nullable type including String

Elm: Nothing only inhabits the Maybe type, there are no null strings, only strings inside Maybes

int? test = null;

Console.Write(test.Value);

//Kaboom! InvalidOperationException

test :: Maybe Int
test = Nothing

Debug.log "test" test

//Outputs Nothing

Are maybes like Nullables?

No - there is no unsafe equivalent of .Value

What's less than ideal about Typescript?

Unsound
type inference less good than H-M
Doesn't control side effects
Doesn't facilitate equational reasoning
Doesn't provide referential transparency
Lacks decent support for ADTs