Either (effect)

型

Either<R, L>

気持ちはわかるが

constructor

code:ts

const foo = Either.right(42);

条件分岐

code:ts

if (Either.isLeft(foo)) {

} else {

}

code:ts

const message = Either.match(foo, {

});

map

map

code:ts

const rightResult = Either.map(Either.right(1), (n) => n + 1);'

mapLeft

ある

mapBoth

code:ts

const transformedRight = Either.mapBoth(Either.right(1), {

onLeft: (s) => s + "!",

onRight: (n) => n + 1,

});

なので、Effect関連の関数をEitherに適用できる

code:ts

const head = <A>(array: ReadonlyArray<A>): Either.Either<A, string> =>

const fetchData = (): Effect.Effect<string, string> => {

const success = Math.random() > 0.5;

return success

? Effect.succeed("some data")

: Effect.fail("Failed to fetch data");

};

Effect.runPromise(program).then(console.log);

/*

Example Output:

*/

code:ts

import { Either } from "effect"

const maybeName: Either.Either<string, string> = Either.right("John")

const maybeAge: Either.Either<number, string> = Either.right(25)

// ▼

console.log(tuple)

/*

Output:

*/

// ┌─── Either<{ name: string; age: number; }, string>

// ▼

const struct = Either.all({ name: maybeName, age: maybeAge })

console.log(struct)

/*

Output:

{ _id: 'Either', _tag: 'Right', right: { name: 'John', age: 25 } }

*/

do記法できる

code:ts

const maybeName: Either.Either<string, string> = Either.right("John");

const maybeAge: Either.Either<number, string> = Either.right(25);

const program = Either.gen(function* () {

const name = (yield* maybeName).toUpperCase();

const age = yield* maybeAge;

return { name, age };

});