/**
 * Test if a variable is an array
 * @param a - The variable to test
 * @return If `true` the variable is an array.
 */
export declare const isArray: (a: unknown) => a is unknown[];
/**
 * Test if a variable is a function
 * @param f - The variable to test
 * @return If `true` the variable is a function.
 */
export declare const isFunction: (f: unknown) => f is (...rest: unknown[]) => unknown;
/**
 * Tests if a string is a valid HEX color encoding
 * @param hex - HEX-encoded color string.
 * @return If `true` the string is a valid HEX color encoding.
 */
export declare const isHex: (hex: string) => boolean;
/**
 * Tests if a number is in `[0,1]`.
 * @param x - Number to be tested.
 * @return If `true` the number is in `[0,1]`.
 */
export declare const isNormFloat: (x: number) => boolean;
/**
 * Tests if an array consist of normalized numbers that are in `[0,1]` only.
 * @param a - Array to be tested
 * @return If `true` the array contains only numbers in `[0,1]`.
 */
export declare const isNormFloatArray: (a: number[]) => boolean;
/**
 * Test if a variable is a number
 * @param x - Variable to be tested
 * @return If `true`, `x` is a number.
 */
export declare const isNumber: (x: unknown) => x is number;
/**
 * Test if a variable is a plain object, e.g., `{}`
 * @param o - The variable to test
 * @return If `true` the variable is a plain object.
 */
export declare const isObject: <T extends {}>(o: unknown) => o is T;
/**
 * Tests if an array is encoding an RGB color.
 * @param rgb - Array to be tested
 * @return If `true` the array hold a triple of Uint8 numbers or
 *   a triple of normalized floats.
 */
export declare const isRgbArray: (rgb: number[]) => boolean;
/**
 * Tests if an array is encoding an RGBA color.
 * @param rgba - Array to be tested
 * @return If `true` the array hold a quadruple of normalized floats,
 *   a quadruple of Uint8s, or a triple of Uint8 and one normalized float.
 */
export declare const isRgbaArray: (rgba: number[]) => boolean;
/**
 * Tests if a string is encoding an RGB color.
 * @param str - String to be tested
 * @return If `true` the array hold a triple of Uint8 numbers or
 *   a triple of normalized floats.
 */
export declare const isRgbStr: (str: string) => boolean;
/**
 * Tests if a string is encoding an RGBA color.
 * @param str - String to be tested
 * @return If `true` the array hold a quadruple of Uint8 numbers or
 *   a quadruple of normalized floats.
 */
export declare const isRgbaStr: (str: string) => boolean;
/**
 * Tests if a variable is a string
 * @param s - Variable to be tested
 * @return If `true` variable is a string
 */
export declare const isString: (s: unknown) => s is string;
/**
 * Tests if a number is an interger and in `[0,255]`.
 * @param x - Number to be tested.
 * @return If `true` the number is an interger and in `[0,255]`.
 */
export declare const isUint8: (x: number) => boolean;
/**
 * Tests if an array consist of Uint8 numbers only.
 * @param a - Array to be tested.
 * @return If `true` the array contains only Uint8 numbers.
 */
export declare const isUint8Array: (a: number[]) => boolean;