Created
May 9, 2020 16:24
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Functor: Compose a pure function with an effectful function
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| import { Option, isNone, none, some } from "fp-ts/lib/Option"; | |
| // Here we lift a pure function to work with Option | |
| // Taken from https://dev.to/gcanti/getting-started-with-fp-ts-functor-36ek | |
| function lift<A, B>(f: (a: A) => B): (fa: Option<A>) => Option<B> { | |
| return (fa) => (isNone(fa) ? none : some(f(fa.value))); | |
| } | |
| const effectfulDouble = (x: number) => some(x * 2); | |
| const pureSay = (x: number) => `The result is ${x}`; | |
| // Let's compose the two functions | |
| const liftedSay = lift(pureSay); | |
| liftedSay(effectfulDouble(5)); // { _tag: 'Some', value: 'The result is 10' } |
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