Function flatMap

flatMap<R extends UnknownTernaryResult, S2, W2, E2>(
result: R,
flatMapFn: (value: UnwrapOk<R>) => TernaryResult<S2, E2, W2>,
): TernaryResult<S2, E2 | UnwrapErr<R>, W2 | UnwrapWarn<R>>

Applies a function returning a TernaryResult to the Ok variant.

Type Parameters

R extends UnknownTernaryResult
S2
W2
E2

Parameters

result: R
flatMapFn: (value: UnwrapOk<R>) => TernaryResult<S2, E2, W2>

Returns TernaryResult<S2, E2 | UnwrapErr<R>, W2 | UnwrapWarn<R>>

Example

const parse = (value: string): TernaryResult<number, string, string> =>
  Number.isNaN(Number(value))
    ? TernaryResult.err('NaN')
    : TernaryResult.ok(Number(value));

const doubled = TernaryResult.flatMap(TernaryResult.ok('3'), (text) =>
  TernaryResult.map(parse(text), (num) => num * 2),
);

const warnPassthrough = TernaryResult.flatMap(
  TernaryResult.warn('3', 'retry'),
  parse,
);

const errPassthrough = TernaryResult.flatMap(TernaryResult.err('oops'), parse);

assert.deepStrictEqual(doubled, TernaryResult.ok(6));

assert.deepStrictEqual(warnPassthrough, TernaryResult.warn(3, 'retry'));

assert.deepStrictEqual(errPassthrough, TernaryResult.err('oops'));

flatMap<S, S2, W2, E2>(
flatMapFn: (value: S) => TernaryResult<S2, E2, W2>,
): <W, E>(
result: TernaryResult<S, E, W>,
) => TernaryResult<S2, E2 | E, W2 | W>

Applies a function returning a TernaryResult to the Ok variant.

Type Parameters

Parameters

flatMapFn: (value: S) => TernaryResult<S2, E2, W2>

Returns <W, E>(result: TernaryResult<S, E, W>) => TernaryResult<S2, E2 | E, W2 | W>

Example

const parse = (value: string): TernaryResult<number, string, string> =>
  Number.isNaN(Number(value))
    ? TernaryResult.err('NaN')
    : TernaryResult.ok(Number(value));

const doubled = TernaryResult.flatMap(TernaryResult.ok('3'), (text) =>
  TernaryResult.map(parse(text), (num) => num * 2),
);

const warnPassthrough = TernaryResult.flatMap(
  TernaryResult.warn('3', 'retry'),
  parse,
);

const errPassthrough = TernaryResult.flatMap(TernaryResult.err('oops'), parse);

assert.deepStrictEqual(doubled, TernaryResult.ok(6));

assert.deepStrictEqual(warnPassthrough, TernaryResult.warn(3, 'retry'));

assert.deepStrictEqual(errPassthrough, TernaryResult.err('oops'));

Function flatMap

Type Parameters

Parameters

Returns TernaryResult<S2, E2 | UnwrapErr<R>, W2 | UnwrapWarn<R>>

Example

Type Parameters

Parameters

Returns <W, E>(result: TernaryResult<S, E, W>) => TernaryResult<S2, E2 | E, W2 | W>

Example

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