ts-data-forge/dist/functional/optional/impl/optional-filter.d.mts

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import { type Unwrap } from './types.mjs';
/**
 * Filters an `Optional` based on a predicate. If the `Optional` is `Some` and
 * the predicate returns true, returns the original `Optional`. Otherwise
 * returns `None`.
 *
 * @example
 *
 * ```ts
 * const even = Optional.filter(Optional.some(4), (value) => value % 2 === 0);
 *
 * const odd = Optional.filter(Optional.some(3), (value) => value % 2 === 0);
 *
 * assert.deepStrictEqual(even, Optional.some(4));
 *
 * assert.deepStrictEqual(odd, Optional.none);
 *
 * const filterEven = Optional.filter((value: number) => value % 2 === 0);
 *
 * assert.deepStrictEqual(filterEven(Optional.some(6)), Optional.some(6));
 *
 * assert.deepStrictEqual(filterEven(Optional.some(5)), Optional.none);
 * ```
 *
 * @template O The input `UnknownOptional` type.
 * @param optional The `Optional` to filter.
 * @param predicate The predicate function.
 * @returns The filtered `Optional`.
 */
export declare function filter<O extends UnknownOptional>(optional: O, predicate: (value: Unwrap<O>) => boolean): Optional<Unwrap<O>>;
export declare function filter<S>(predicate: (value: S) => boolean): (optional: Optional<S>) => Optional<S>;
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