hexlet-pairs/dist/index.js

## Install

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.toString = exports.cdr = exports.car = exports.cons = exports.checkPair = exports.isPair = void 0;

function _typeof(obj) { if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") { _typeof = function _typeof(obj) { return typeof obj; }; } else { _typeof = function _typeof(obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; }; } return _typeof(obj); }

/**
 * Check if something is pair
 * @example
 * const pair = cons(5, 'hello');
 * isPair(pair); // true
 * isPair(5); // false
 */
var isPair = function isPair(pair) {
  return typeof pair === 'function' && pair.pair;
};

exports.isPair = isPair;

var checkPair = function checkPair(pair) {
  if (!isPair(pair)) {
    var value = _typeof(pair) === 'object' ? JSON.stringify(pair, null, 2) : String(pair);
    throw new Error("Argument must be pair, but it was '".concat(value, "'"));
  }
};
/**
 * Build pair
 * @example
 * const pair = cons(5, 'hello');
 * @example
 * const pair = cons(cons(1, null), 'world');
 */


exports.checkPair = checkPair;

var cons = function cons(a, b) {
  var pair = function pair(message) {
    switch (message) {
      case 'car':
        return a;

      case 'cdr':
        return b;

      default:
        throw new Error("Unknown message '".concat(message, "'"));
    }
  };

  pair.pair = true;
  return pair;
};
/**
 * Get car (first element) from pair
 * @example
 * const pair = cons(5, 'hello');
 * car(pair); // 5
 */


exports.cons = cons;

var car = function car(pair) {
  checkPair(pair);
  return pair('car');
};
/**
 * Get cdr (second element) from pair
 * @example
 * const pair = cons(5, 'hello');
 * cdr(pair); // hello
 */


exports.car = car;

var cdr = function cdr(pair) {
  checkPair(pair);
  return pair('cdr');
};
/**
 * Convert pair to string (recursively)
 * @example
 * toString(cons('', 10)); // ('', 10)
 */


exports.cdr = cdr;

var toString = function toString(pair) {
  checkPair(pair);

  var rec = function rec(p) {
    if (!isPair(p)) {
      return String(p);
    }

    var left = car(p);
    var right = cdr(p);
    return "(".concat(rec(left), ", ").concat(rec(right), ")");
  };

  return rec(pair);
};

exports.toString = toString;

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