iterama/web/take.js

Composable functional (async) iterable helpers

import _defineProperty from "@babel/runtime/helpers/esm/defineProperty";

function _createForOfIteratorHelper(o, allowArrayLike) { var it; if (typeof Symbol === "undefined" || o[Symbol.iterator] == null) { if (Array.isArray(o) || (it = _unsupportedIterableToArray(o)) || allowArrayLike && o && typeof o.length === "number") { if (it) o = it; var i = 0; var F = function F() {}; return { s: F, n: function n() { if (i >= o.length) return { done: true }; return { done: false, value: o[i++] }; }, e: function e(_e) { throw _e; }, f: F }; } throw new TypeError("Invalid attempt to iterate non-iterable instance.\nIn order to be iterable, non-array objects must have a [Symbol.iterator]() method."); } var normalCompletion = true, didErr = false, err; return { s: function s() { it = o[Symbol.iterator](); }, n: function n() { var step = it.next(); normalCompletion = step.done; return step; }, e: function e(_e2) { didErr = true; err = _e2; }, f: function f() { try { if (!normalCompletion && it.return != null) it.return(); } finally { if (didErr) throw err; } } }; }

function _unsupportedIterableToArray(o, minLen) { if (!o) return; if (typeof o === "string") return _arrayLikeToArray(o, minLen); var n = Object.prototype.toString.call(o).slice(8, -1); if (n === "Object" && o.constructor) n = o.constructor.name; if (n === "Map" || n === "Set") return Array.from(o); if (n === "Arguments" || /^(?:Ui|I)nt(?:8|16|32)(?:Clamped)?Array$/.test(n)) return _arrayLikeToArray(o, minLen); }

function _arrayLikeToArray(arr, len) { if (len == null || len > arr.length) len = arr.length; for (var i = 0, arr2 = new Array(len); i < len; i++) { arr2[i] = arr[i]; } return arr2; }

import FixedArray from 'circularr';
import { iterate } from './iterate';

var takeFirst = function takeFirst(n) {
  return function (iterable) {
    return _defineProperty({}, Symbol.iterator, function* () {
      if (n <= 0) {
        return;
      }

      var i = 0;

      var _iterator = _createForOfIteratorHelper(iterable),
          _step;

      try {
        for (_iterator.s(); !(_step = _iterator.n()).done;) {
          var value = _step.value;
          yield value;

          if (++i >= n) {
            break;
          }
        }
      } catch (err) {
        _iterator.e(err);
      } finally {
        _iterator.f();
      }
    });
  };
};

var takeLast = function takeLast(n) {
  return function (iterable) {
    return _defineProperty({}, Symbol.iterator, function* () {
      var last = new FixedArray(n);
      var numValues = 0;

      var _iterator2 = _createForOfIteratorHelper(iterable),
          _step2;

      try {
        for (_iterator2.s(); !(_step2 = _iterator2.n()).done;) {
          var value = _step2.value;
          last.shift(value);
          ++numValues;
        } // skip empty values

      } catch (err) {
        _iterator2.e(err);
      } finally {
        _iterator2.f();
      }

      var iterator = iterate(last);
      var offset = last.length - numValues;

      for (var i = 0; i < offset; i++) {
        iterator.next();
      } // actual values


      var _iterator3 = _createForOfIteratorHelper(iterator),
          _step3;

      try {
        for (_iterator3.s(); !(_step3 = _iterator3.n()).done;) {
          var _value = _step3.value;
          yield _value;
        }
      } catch (err) {
        _iterator3.e(err);
      } finally {
        _iterator3.f();
      }
    });
  };
};

export var take = function take(n) {
  return n < 0 ? takeLast(-n) : takeFirst(n);
};
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