premap

import { premap } from "https://github.gh-proxy.cn/raw.githubusercontent.com/baetheus/fun/main/fn_either.ts";

Map over the input value of a FnEither.

@example

import * as FE from "./fn_either.ts";
import { pipe } from "./fn.ts";

// This has type FnEither<[Date], never, number>
const computation = pipe(
  FE.id<number>(),
  FE.premap((d: Date) => d.valueOf()),
);

const result = computation(new Date(0)); // Right(0)

function premap<L, D>(fld: (l: L) => D): <A, B>(ua: FnEither<D, B, A>) => FnEither<L, B, A>;

premap<L, D>(fld: (l: L) => D): <A, B>(ua: FnEither<D, B, A>) => FnEither<L, B, A>

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§Type Parameters

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§Parameters

fld: (l: L) => D

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§Return Type

<A, B>(ua: FnEither<D, B, A>) => FnEither<L, B, A>

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