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
1
1
1 + 1 = 2
1 + 1 = 2
1
2
2
2 * 2 = 4
1 + 4 = 5
Cardinality
String test = null;
//vs
test = NothingC#: 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
Intro to Elm
By Julian Jelfs
