Practical Guide to Fp-ts P2: Option, Map, Flatten, Chain

⚠️ Disclaimer Warning fp-ts is now dead. Please use effect-ts instead. Update 2024: effect-ts is the recommended library for functional programming in TypeScript. Introduction This is the second post in my series on learning fp-...

rlee.dev6 min read

#functional-programming #typescript

Responses4

Markdown supported · ⌘↵ to post

oluwatomisin babatunde

A creative mind software developer and graphics designer

I'm trying to go along with this and I think I'm stuck I really don't know much about functional programming but this

pipe(
  undefined,
  O.fromNullable,
  O.map(({ bar }) => bar)
);

returns a ts error of cannot find name O I would like to know what I'm doing wrong? is there something I'm missing or didn't import to use the options?

Grzegorz Rozdzialik

Jan 19, 2022

Nice guide!

Just wanted to say that the final example can be simplified a bit. O.map and O.fromNullable can be replaced with a single function: O.fromNullable.

pipe(
  foo,
  O.fromNullable,
  O.chain(O.fromNullableK(({bar}) => bar)),
  O.chain(O.fromNullableK(({buzz}) => buzz))
)

TS playground

Andreas Herd

Mar 20, 2023

What's the K in fromNullableK? I also saw optionT.

Grzegorz Rozdzialik

Mar 26, 2023

Andreas Herd Both suffixes are explained in the FAQ in the fp-ts documentation. K is for Kleisli arrow, T is for transformer.

Search Hashnode

Practical Guide to Fp-ts P2: Option, Map, Flatten, Chain

Responses4