/**
 * The `Eq` type class represents types which support decidable equality.
 *
 * Instances must satisfy the following laws:
 *
 * 1. Reflexivity: `E.equals(a, a) === true`
 * 2. Symmetry: `E.equals(a, b) === E.equals(b, a)`
 * 3. Transitivity: if `E.equals(a, b) === true` and `E.equals(b, c) === true`, then `E.equals(a, c) === true`
 *
 * @since 2.0.0
 */
import { Contravariant1 } from './Contravariant'
import { Monoid } from './Monoid'
import { ReadonlyRecord } from './ReadonlyRecord'
/**
 * @category type classes
 * @since 2.0.0
 */
export interface Eq<A> {
  readonly equals: (x: A, y: A) => boolean
}
/**
 * @category constructors
 * @since 2.0.0
 */
export declare function fromEquals<A>(equals: (x: A, y: A) => boolean): Eq<A>
/**
 * @category Contravariant
 * @since 2.0.0
 */
export declare const contramap: <A, B>(f: (b: B) => A) => (fa: Eq<A>) => Eq<B>
/**
 * @category instances
 * @since 2.0.0
 */
export declare const URI = 'Eq'
/**
 * @category instances
 * @since 2.0.0
 */
export declare type URI = typeof URI
declare module './HKT' {
  interface URItoKind<A> {
    readonly [URI]: Eq<A>
  }
}
/**
 * @category instances
 * @since 2.5.0
 */
export declare const eqStrict: Eq<unknown>
/**
 * Use `eqStrict` instead
 *
 * @since 2.0.0
 * @deprecated
 */
export declare function strictEqual<A>(a: A, b: A): boolean
/**
 * @category instances
 * @since 2.0.0
 */
export declare const eqString: Eq<string>
/**
 * @category instances
 * @since 2.0.0
 */
export declare const eqNumber: Eq<number>
/**
 * @category instances
 * @since 2.0.0
 */
export declare const eqBoolean: Eq<boolean>
/**
 * @category instances
 * @since 2.0.0
 */
export declare function getStructEq<O extends ReadonlyRecord<string, any>>(
  eqs: {
    [K in keyof O]: Eq<O[K]>
  }
): Eq<O>
/**
 * Given a tuple of `Eq`s returns a `Eq` for the tuple
 *
 * @example
 * import { getTupleEq, eqString, eqNumber, eqBoolean } from 'fp-ts/Eq'
 *
 * const E = getTupleEq(eqString, eqNumber, eqBoolean)
 * assert.strictEqual(E.equals(['a', 1, true], ['a', 1, true]), true)
 * assert.strictEqual(E.equals(['a', 1, true], ['b', 1, true]), false)
 * assert.strictEqual(E.equals(['a', 1, true], ['a', 2, true]), false)
 * assert.strictEqual(E.equals(['a', 1, true], ['a', 1, false]), false)
 *
 * @category instances
 * @since 2.0.0
 */
export declare function getTupleEq<T extends ReadonlyArray<Eq<any>>>(
  ...eqs: T
): Eq<
  {
    [K in keyof T]: T[K] extends Eq<infer A> ? A : never
  }
>
/**
 * @category instances
 * @since 2.0.0
 */
export declare const eqDate: Eq<Date>
/**
 * @category instances
 * @since 2.6.0
 */
export declare function getMonoid<A>(): Monoid<Eq<A>>
/**
 * @category instances
 * @since 2.7.0
 */
export declare const Contravariant: Contravariant1<URI>
/**
 * @category instances
 * @since 2.0.0
 */
export declare const eq: Contravariant1<URI>