import type * as P from "@principia/prelude";
import type { Either, URI, V } from "./model";
/**
 * ```haskell
 * extend_ :: Extend w => (w a, (w a -> b)) -> w b
 * ```
 *
 * @category Extend
 * @since 1.0.0
 */
export declare const extend_: <E, A, B>(wa: Either<E, A>, f: (wa: Either<E, A>) => B) => Either<E, B>;
/**
 * ```haskell
 * extend :: Extend w => (w a -> b) -> w a -> w b
 * ```
 *
 * @category Extend
 * @since 1.0.0
 */
export declare const extend: <E, A, B>(f: (wa: Either<E, A>) => B) => (wa: Either<E, A>) => Either<E, B>;
/**
 * ```haskell
 * duplicate :: Extend w => w a -> w (w a)
 * ```
 *
 * @category Extend
 * @since 1.0.0
 */
export declare const duplicate: <E, A>(wa: Either<E, A>) => Either<E, Either<E, A>>;
/**
 * @category Instances
 * @since 1.0.0
 */
export declare const Extend: P.Extend<[URI], V>;
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