curry.js

import createWrap from './.internal/createWrap.js'

/** Used to compose bitmasks for function metadata. */
const WRAP_CURRY_FLAG = 8

/**
 * Creates a function that accepts arguments of `func` and either invokes
 * `func` returning its result, if at least `arity` number of arguments have
 * been provided, or returns a function that accepts the remaining `func`
 * arguments, and so on. The arity of `func` may be specified if `func.length`
 * is not sufficient.
 *
 * The `curry.placeholder` value, which defaults to `_` in monolithic builds,
 * may be used as a placeholder for provided arguments.
 *
 * **Note:** This method doesn't set the "length" property of curried functions.
 *
 * @since 2.0.0
 * @category Function
 * @param {Function} func The function to curry.
 * @param {number} [arity=func.length] The arity of `func`.
 * @returns {Function} Returns the new curried function.
 * @example
 *
 * const abc = function(a, b, c) {
 *   return [a, b, c]
 * }
 *
 * const curried = curry(abc)
 *
 * curried(1)(2)(3)
 * // => [1, 2, 3]
 *
 * curried(1, 2)(3)
 * // => [1, 2, 3]
 *
 * curried(1, 2, 3)
 * // => [1, 2, 3]
 *
 * // Curried with placeholders.
 * curried(1)(_, 3)(2)
 * // => [1, 2, 3]
 */
function curry(func, arity) {
  const result = createWrap(func, WRAP_CURRY_FLAG, undefined, undefined, undefined, undefined, undefined, arity)
  result.placeholder = curry.placeholder
  return result
}

// Assign default placeholders.
curry.placeholder = {}

export default curry