import type { Either } from "../Either";
import type { Lazy } from "../Function";
import type { Option } from "./model";
/**
 * mapNullable_ :: Maybe m => (m a, (a -> ?b)) -> m b
 * Map over a Maybe with a function that returns a nullable value
 *
 * @category Combinators
 * @since 1.0.0
 */
export declare const mapNullable_: <A, B>(fa: Option<A>, f: (a: A) => B | null | undefined) => Option<B>;
/**
 * mapNullable :: Maybe m => (a -> ?b) -> m a -> m b
 * Map over a Maybe with a function that returns a nullable value
 *
 * @category Combinators
 * @since 1.0.0
 */
export declare const mapNullable: <A, B>(f: (a: A) => B | null | undefined) => (fa: Option<A>) => Option<B>;
/**
 * orElse_ :: Maybe m => (m a, () -> m b) -> m (a | b)
 * Evaluate and return alternate optional value if empty
 *
 * @category Combinators
 * @since 1.0.0
 */
export declare const orElse_: <A, B>(fa: Option<A>, onNothing: Lazy<Option<B>>) => Option<A | B>;
/**
 * orElse :: Maybe m => (() -> m b) -> m a -> m (a | b)
 * Evaluate and return alternate optional value if empty
 *
 * @category Combinators
 * @since 1.0.0
 */
export declare const orElse: <B>(onNothing: Lazy<Option<B>>) => <A>(fa: Option<A>) => Option<B | A>;
/**
 * getLeft :: (Either e, Maybe m) => e a b -> m a
 * Evaluates an `Either` and returns a `Maybe` carrying the left value, if it exists
 *
 * @category Combinators
 * @since 1.0.0
 */
export declare const getLeft: <E, A>(fea: Either<E, A>) => Option<E>;
/**
 * getRight :: (Either e, Maybe m) => e a b -> m b
 * Evaluates an `Either` and returns a `Maybe` carrying the right value, if it exists
 *
 * @category Combinators
 * @since 1.0.0
 */
export declare const getRight: <E, A>(fea: Either<E, A>) => Option<A>;
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