/**
 * ```ts
 * interface IO<A> {
 *   (): A
 * }
 * ```
 *
 * `IO<A>` represents a non-deterministic synchronous computation that can cause side effects, yields a value of
 * type `A` and **never fails**.
 *
 * If you want to represent a synchronous computation that may fail, please see `IOEither`.
 * If you want to represent a synchronous computation that may yield nothing, please see `IOOption`.
 *
 * @since 2.0.0
 */
import { Applicative1 } from './Applicative.js';
import { Apply1 } from './Apply.js';
import * as chainable from './Chain.js';
import { ChainRec1 } from './ChainRec.js';
import { FromIO1 } from './FromIO.js';
import { Functor1 } from './Functor.js';
import { Monad1 } from './Monad.js';
import { MonadIO1 } from './MonadIO.js';
import { Monoid } from './Monoid.js';
import { Pointed1 } from './Pointed.js';
import { ReadonlyNonEmptyArray } from './ReadonlyNonEmptyArray.js';
import { Semigroup } from './Semigroup.js';
/**
 * @category model
 * @since 2.0.0
 */
export interface IO<A> {
    (): A;
}
/**
 * `map` can be used to turn functions `(a: A) => B` into functions `(fa: F<A>) => F<B>` whose argument and return types
 * use the type constructor `F` to represent some computational context.
 *
 * @category mapping
 * @since 2.0.0
 */
export declare const map: <A, B>(f: (a: A) => B) => (fa: IO<A>) => IO<B>;
/**
 * @since 2.0.0
 */
export declare const ap: <A>(fa: IO<A>) => <B>(fab: IO<(a: A) => B>) => IO<B>;
/**
 * @category constructors
 * @since 2.0.0
 */
export declare const of: <A>(a: A) => IO<A>;
/**
 * @category sequencing
 * @since 2.14.0
 */
export declare const flatMap: {
    <A, B>(f: (a: A) => IO<B>): (ma: IO<A>) => IO<B>;
    <A, B>(ma: IO<A>, f: (a: A) => IO<B>): IO<B>;
};
/**
 * @category sequencing
 * @since 2.0.0
 */
export declare const flatten: <A>(mma: IO<IO<A>>) => IO<A>;
/**
 * @category type lambdas
 * @since 2.0.0
 */
export declare const URI = "IO";
/**
 * @category type lambdas
 * @since 2.0.0
 */
export type URI = typeof URI;
declare module './HKT.js' {
    interface URItoKind<A> {
        readonly [URI]: IO<A>;
    }
}
/**
 * @category instances
 * @since 2.7.0
 */
export declare const Functor: Functor1<URI>;
/**
 * Maps the value to the specified constant value.
 *
 * @category mapping
 * @since 2.16.0
 */
export declare const as: {
    <A>(a: A): <_>(self: IO<_>) => IO<A>;
    <_, A>(self: IO<_>, a: A): IO<A>;
};
/**
 * Maps the value to the void constant value.
 *
 * @category mapping
 * @since 2.16.0
 */
export declare const asUnit: <_>(self: IO<_>) => IO<void>;
/**
 * @category mapping
 * @since 2.10.0
 */
export declare const flap: <A>(a: A) => <B>(fab: import("./HKT.js").Kind<"IO", (a: A) => B>) => import("./HKT.js").Kind<"IO", B>;
/**
 * @category instances
 * @since 2.10.0
 */
export declare const Pointed: Pointed1<URI>;
/**
 * @category instances
 * @since 2.10.0
 */
export declare const Apply: Apply1<URI>;
/**
 * Combine two effectful actions, keeping only the result of the first.
 *
 * @since 2.0.0
 */
export declare const apFirst: <B>(second: IO<B>) => <A>(first: import("./HKT.js").Kind<"IO", A>) => import("./HKT.js").Kind<"IO", A>;
/**
 * Combine two effectful actions, keeping only the result of the second.
 *
 * @since 2.0.0
 */
export declare const apSecond: <B>(second: IO<B>) => <A>(first: import("./HKT.js").Kind<"IO", A>) => import("./HKT.js").Kind<"IO", B>;
/**
 * @category instances
 * @since 2.7.0
 */
export declare const Applicative: Applicative1<URI>;
/**
 * @category instances
 * @since 2.10.0
 */
export declare const Chain: chainable.Chain1<URI>;
/**
 * @category instances
 * @since 2.7.0
 */
export declare const Monad: Monad1<URI>;
/**
 * Composes computations in sequence, using the return value of one computation to determine the next computation and
 * keeping only the result of the first.
 *
 * @category combinators
 * @since 2.15.0
 */
export declare const tap: {
    <A, _>(self: IO<A>, f: (a: A) => IO<_>): IO<A>;
    <A, _>(f: (a: A) => IO<_>): (self: IO<A>) => IO<A>;
};
/**
 * @category zone of death
 * @since 2.7.0
 * @deprecated
 */
export declare const fromIO: <A>(fa: IO<A>) => IO<A>;
/**
 * @category instances
 * @since 2.7.0
 */
export declare const MonadIO: MonadIO1<URI>;
/**
 * @category instances
 * @since 2.7.0
 */
export declare const ChainRec: ChainRec1<URI>;
/**
 * @category instances
 * @since 2.10.0
 */
export declare const FromIO: FromIO1<URI>;
/**
 * @category do notation
 * @since 2.9.0
 */
export declare const Do: IO<{}>;
/**
 * @category do notation
 * @since 2.8.0
 */
export declare const bindTo: <N extends string>(name: N) => <A>(fa: import("./HKT.js").Kind<"IO", A>) => import("./HKT.js").Kind<"IO", { readonly [K in N]: A; }>;
declare const let_: <N extends string, A, B>(name: Exclude<N, keyof A>, f: (a: A) => B) => (fa: import("./HKT.js").Kind<"IO", A>) => import("./HKT.js").Kind<"IO", { readonly [K in keyof A | N]: K extends keyof A ? A[K] : B; }>;
export { 
/**
 * @category do notation
 * @since 2.13.0
 */
let_ as let };
/**
 * @category do notation
 * @since 2.8.0
 */
export declare const bind: <N extends string, A, B>(name: Exclude<N, keyof A>, f: (a: A) => import("./HKT.js").Kind<"IO", B>) => (ma: import("./HKT.js").Kind<"IO", A>) => import("./HKT.js").Kind<"IO", { readonly [K in keyof A | N]: K extends keyof A ? A[K] : B; }>;
/**
 * @category do notation
 * @since 2.8.0
 */
export declare const apS: <N extends string, A, B>(name: Exclude<N, keyof A>, fb: IO<B>) => (fa: import("./HKT.js").Kind<"IO", A>) => import("./HKT.js").Kind<"IO", { readonly [K in keyof A | N]: K extends keyof A ? A[K] : B; }>;
/**
 * @since 2.11.0
 */
export declare const ApT: IO<readonly []>;
/**
 * Equivalent to `ReadonlyNonEmptyArray#traverseWithIndex(Applicative)`.
 *
 * @category traversing
 * @since 2.11.0
 */
export declare const traverseReadonlyNonEmptyArrayWithIndex: <A, B>(f: (index: number, a: A) => IO<B>) => (as: ReadonlyNonEmptyArray<A>) => IO<ReadonlyNonEmptyArray<B>>;
/**
 * Equivalent to `ReadonlyArray#traverseWithIndex(Applicative)`.
 *
 * @category traversing
 * @since 2.11.0
 */
export declare const traverseReadonlyArrayWithIndex: <A, B>(f: (index: number, a: A) => IO<B>) => ((as: ReadonlyArray<A>) => IO<ReadonlyArray<B>>);
/**
 * Equivalent to `ReadonlyArray#traverseWithIndex(Applicative)`.
 *
 * @category traversing
 * @since 2.9.0
 */
export declare const traverseArrayWithIndex: <A, B>(f: (index: number, a: A) => IO<B>) => (as: ReadonlyArray<A>) => IO<ReadonlyArray<B>>;
/**
 * Equivalent to `ReadonlyArray#traverse(Applicative)`.
 *
 * @category traversing
 * @since 2.9.0
 */
export declare const traverseArray: <A, B>(f: (a: A) => IO<B>) => ((as: ReadonlyArray<A>) => IO<ReadonlyArray<B>>);
/**
 * Equivalent to `ReadonlyArray#sequence(Applicative)`.
 *
 * @category traversing
 * @since 2.9.0
 */
export declare const sequenceArray: <A>(arr: ReadonlyArray<IO<A>>) => IO<ReadonlyArray<A>>;
/**
 * Alias of `flatMap`.
 *
 * @category legacy
 * @since 2.0.0
 */
export declare const chain: <A, B>(f: (a: A) => IO<B>) => (ma: IO<A>) => IO<B>;
/**
 * Alias of `tap`.
 *
 * @category legacy
 * @since 2.0.0
 */
export declare const chainFirst: <A, B>(f: (a: A) => IO<B>) => (first: IO<A>) => IO<A>;
/**
 * This instance is deprecated, use small, specific instances instead.
 * For example if a function needs a `Functor` instance, pass `IO.Functor` instead of `IO.io`
 * (where `IO` is from `import IO from 'fp-ts/IO'`)
 *
 * @category zone of death
 * @since 2.0.0
 * @deprecated
 */
export declare const io: Monad1<URI> & MonadIO1<URI> & ChainRec1<URI>;
/**
 * Use [`getApplySemigroup`](./Apply.ts.html#getapplysemigroup) instead.
 *
 * @category zone of death
 * @since 2.0.0
 * @deprecated
 */
export declare const getSemigroup: <A>(S: Semigroup<A>) => Semigroup<IO<A>>;
/**
 * Use [`getApplicativeMonoid`](./Applicative.ts.html#getapplicativemonoid) instead.
 *
 * @category zone of death
 * @since 2.0.0
 * @deprecated
 */
export declare const getMonoid: <A>(M: Monoid<A>) => Monoid<IO<A>>;