thunkify.js

import curryN from './curryN';
import _curry1 from './internal/_curry1';

/**
 * Creates a thunk out of a function. A thunk delays a calculation until
 * its result is needed, providing lazy evaluation of arguments.
 *
 * @func
 * @memberOf R
 * @category Function
 * @sig ((a, b, ..., j) -> k) -> (a, b, ..., j) -> (() -> k)
 * @param {Function} fn A function to wrap in a thunk
 * @return {Function} Expects arguments for `fn` and returns a new function
 *  that, when called, applies those arguments to `fn`.
 * @see R.partial, R.partialRight
 * @example
 *
 *      R.thunkify(R.identity)(42)(); //=> 42
 *      R.thunkify((a, b) => a + b)(25, 17)(); //=> 42
 */
var thunkify = _curry1(function thunkify(fn) {
  return curryN(fn.length, function createThunk() {
    var fnArgs = arguments;
    return function invokeThunk() {
      return fn.apply(this, fnArgs);
    };
  });
});

export default thunkify;