import { SafeInteger } from "../../numbers";
/**
 * Provides basic methods to compare the equality of two objects.
 *
 * @remarks
 * While it is theoretically possible to let a {@link !Function} implement this interface,
 * this can interfere with the overload resolution logic and thus not recommended.
 *
 * @see {@link HashableEqualityComparer}
 */
export interface EqualityComparer<T = any> {
    /**
     * Compares the equality of two objects.
     *
     * @returns
     * * `true` if `x` is equal to `y`.
     * * `false` if `x` is not equal to `y`.
     */
    equals(x: T, y: T): boolean;
    /**
     * Given an aribtrary value, checks whether the value can be compared by the current {@link EqualityComparer}.
     */
    isSupported(value: unknown): value is T;
}
/**
 * Provides methods to compare the equality of two objects, along with a function
 * to hash the objects for hash map implementation.
 *
 * @remarks
 * Due to the limitation of current JavaScript API, there is no efficient approach to evaluate
 * hash code for every primitive types (e.g. `string`). This can cause significant performance penalty.
 *
 * @see {@link EqualityComparer}
 */
export interface HashableEqualityComparer<T = any> extends EqualityComparer<T> {
    /**
     * Compares the equality of two objects.
     *
     * @returns
     * * `true` if `x` is equal to `y`.
     * * `false` if `x` is not equal to `y`.
     */
    equals(x: T, y: T): boolean;
    /**
     * Evaluates the hash code for the specified `value`.
     *
     * @remarks Implementations are required to ensure that if {@link equals} returns `true` for two values `x` and `y`,
     * then the value returned by {@link getHashCode} for `x` must equal the value returned for `y`.
     */
    getHashCode(value: T): SafeInteger;
    /**
     * Given an aribtrary value, checks whether the value can be compared by the current {@link HashableEqualityComparer}.
     */
    isSupported(value: unknown): value is T;
}
export declare const EqualsSymbol: unique symbol;
export declare const GetHashCodeSymbol: unique symbol;
export interface Equatable {
    [EqualsSymbol](other: unknown): boolean;
    [GetHashCodeSymbol]?(): SafeInteger;
}
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