/**
 * Validate that the value is an empty value.
 *
 * @param value The value to check.
 * @returns True if the value is an empty value, false otherwise.
 */
export declare function isEmptyValue(value: unknown): value is null | undefined;
/**
 * Validate that the value is a non-empty value.
 *
 * @param value The value to check.
 * @returns True if the value is a non-empty value, false otherwise.
 */
export declare function isNonEmptyValue<T>(value: T): value is NonNullable<T>;
/**
 * Validate that the value is a number.
 *
 * @param value The value to check.
 * @returns True if the value is a number, false otherwise.
 */
export declare function isNumber(value: unknown): value is number;
/**
 * Validate that the value is a string. This includes both primitive strings
 * and string objects.
 *
 * @param value The value to check.
 * @returns True if the value is a string, false otherwise.
 */
export declare function isString(value: unknown): value is string;
/**
 * Validate that the value is an empty string. An empty string is a string that
 * contains no characters.
 *
 * @param value The value to check.
 * @returns True if the value is an empty string, false otherwise.
 */
export declare function isEmptyString(value: unknown): value is '';
/**
 * Validate that the value is a blank string. A blank string is a string that
 * contains only whitespace characters.
 *
 * @param value
 * @returns
 */
export declare function isWhitespaceString(value: unknown): boolean;
/**
 * Validate that the value is a string that is non-empty.
 *
 * @param value The value to check.
 * @returns True if the value is a string that is non-empty, false otherwise.
 */
export declare function isNonEmptyString(value: unknown): value is string;