gistfile1.js

function* addGenerator() {
  var i = 0;
  while (true) {
    i += yield i;
  }
}

var adder = addGenerator();
adder.next().value; // 0
adder.next(5).value; // 5
adder.next(5).value; // 10
adder.next(5).value; // 15
adder.next(50).value; // 65

"use strict";

/**
 * Copyright (c) 2014, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * https://raw.github.com/facebook/regenerator/master/LICENSE file. An
 * additional grant of patent rights can be found in the PATENTS file in
 * the same directory.
 */

!(function(global) {
  "use strict";

  var hasOwn = Object.prototype.hasOwnProperty;
  var undefined; // More compressible than void 0.
  var iteratorSymbol =
    typeof Symbol === "function" && Symbol.iterator || "@@iterator";

  var inModule = typeof module === "object";
  var runtime = global.regeneratorRuntime;
  if (runtime) {
    if (inModule) {
      // If regeneratorRuntime is defined globally and we're in a module,
      // make the exports object identical to regeneratorRuntime.
      module.exports = runtime;
    }
    // Don't bother evaluating the rest of this file if the runtime was
    // already defined globally.
    return;
  }

  // Define the runtime globally (as expected by generated code) as either
  // module.exports (if we're in a module) or a new, empty object.
  runtime = global.regeneratorRuntime = inModule ? module.exports : {};

  function wrap(innerFn, outerFn, self, tryList) {
    return new Generator(innerFn, outerFn, self || null, tryList || []);
  }
  runtime.wrap = wrap;

  // Try/catch helper to minimize deoptimizations. Returns a completion
  // record like context.tryEntries[i].completion. This interface could
  // have been (and was previously) designed to take a closure to be
  // invoked without arguments, but in all the cases we care about we
  // already have an existing method we want to call, so there's no need
  // to create a new function object. We can even get away with assuming
  // the method takes exactly one argument, since that happens to be true
  // in every case, so we don't have to touch the arguments object. The
  // only additional allocation required is the completion record, which
  // has a stable shape and so hopefully should be cheap to allocate.
  function tryCatch(fn, obj, arg) {
    try {
      return { type: "normal", arg: fn.call(obj, arg) };
    } catch (err) {
      return { type: "throw", arg: err };
    }
  }

  var GenStateSuspendedStart = "suspendedStart";
  var GenStateSuspendedYield = "suspendedYield";
  var GenStateExecuting = "executing";
  var GenStateCompleted = "completed";

  // Returning this object from the innerFn has the same effect as
  // breaking out of the dispatch switch statement.
  var ContinueSentinel = {};

  // Dummy constructor functions that we use as the .constructor and
  // .constructor.prototype properties for functions that return Generator
  // objects. For full spec compliance, you may wish to configure your
  // minifier not to mangle the names of these two functions.
  function GeneratorFunction() {}
  function GeneratorFunctionPrototype() {}

  var Gp = GeneratorFunctionPrototype.prototype = Generator.prototype;
  GeneratorFunction.prototype = Gp.constructor = GeneratorFunctionPrototype;
  GeneratorFunctionPrototype.constructor = GeneratorFunction;
  GeneratorFunction.displayName = "GeneratorFunction";

  runtime.isGeneratorFunction = function(genFun) {
    var ctor = typeof genFun === "function" && genFun.constructor;
    return ctor
      ? ctor === GeneratorFunction ||
        // For the native GeneratorFunction constructor, the best we can
        // do is to check its .name property.
        (ctor.displayName || ctor.name) === "GeneratorFunction"
      : false;
  };

  runtime.mark = function(genFun) {
    genFun.__proto__ = GeneratorFunctionPrototype;
    genFun.prototype = Object.create(Gp);
    return genFun;
  };

  runtime.async = function(innerFn, outerFn, self, tryList) {
    return new Promise(function(resolve, reject) {
      var generator = wrap(innerFn, outerFn, self, tryList);
      var callNext = step.bind(generator.next);
      var callThrow = step.bind(generator["throw"]);

      function step(arg) {
        var record = tryCatch(this, null, arg);
        if (record.type === "throw") {
          reject(record.arg);
          return;
        }

        var info = record.arg;
        if (info.done) {
          resolve(info.value);
        } else {
          Promise.resolve(info.value).then(callNext, callThrow);
        }
      }

      callNext();
    });
  };

  function Generator(innerFn, outerFn, self, tryList) {
    var generator = outerFn ? Object.create(outerFn.prototype) : this;
    var context = new Context(tryList);
    var state = GenStateSuspendedStart;

    function invoke(method, arg) {
      if (state === GenStateExecuting) {
        throw new Error("Generator is already running");
      }

      if (state === GenStateCompleted) {
        // Be forgiving, per 25.3.3.3.3 of the spec:
        // https://people.mozilla.org/~jorendorff/es6-draft.html#sec-generatorresume
        return doneResult();
      }

      while (true) {
        var delegate = context.delegate;
        if (delegate) {
          var record = tryCatch(
            delegate.iterator[method],
            delegate.iterator,
            arg
          );

          if (record.type === "throw") {
            context.delegate = null;

            // Like returning generator.throw(uncaught), but without the
            // overhead of an extra function call.
            method = "throw";
            arg = record.arg;

            continue;
          }

          // Delegate generator ran and handled its own exceptions so
          // regardless of what the method was, we continue as if it is
          // "next" with an undefined arg.
          method = "next";
          arg = undefined;

          var info = record.arg;
          if (info.done) {
            context[delegate.resultName] = info.value;
            context.next = delegate.nextLoc;
          } else {
            state = GenStateSuspendedYield;
            return info;
          }

          context.delegate = null;
        }

        if (method === "next") {
          if (state === GenStateSuspendedStart &&
              typeof arg !== "undefined") {
            // https://people.mozilla.org/~jorendorff/es6-draft.html#sec-generatorresume
            throw new TypeError(
              "attempt to send " + JSON.stringify(arg) + " to newborn generator"
            );
          }

          if (state === GenStateSuspendedYield) {
            context.sent = arg;
          } else {
            delete context.sent;
          }

        } else if (method === "throw") {
          if (state === GenStateSuspendedStart) {
            state = GenStateCompleted;
            throw arg;
          }

          if (context.dispatchException(arg)) {
            // If the dispatched exception was caught by a catch block,
            // then let that catch block handle the exception normally.
            method = "next";
            arg = undefined;
          }

        } else if (method === "return") {
          context.abrupt("return", arg);
        }

        state = GenStateExecuting;

        var record = tryCatch(innerFn, self, context);
        if (record.type === "normal") {
          // If an exception is thrown from innerFn, we leave state ===
          // GenStateExecuting and loop back for another invocation.
          state = context.done
            ? GenStateCompleted
            : GenStateSuspendedYield;

          var info = {
            value: record.arg,
            done: context.done
          };

          if (record.arg === ContinueSentinel) {
            if (context.delegate && method === "next") {
              // Deliberately forget the last sent value so that we don't
              // accidentally pass it on to the delegate.
              arg = undefined;
            }
          } else {
            return info;
          }

        } else if (record.type === "throw") {
          state = GenStateCompleted;

          if (method === "next") {
            context.dispatchException(record.arg);
          } else {
            arg = record.arg;
          }
        }
      }
    }

    generator.next = invoke.bind(generator, "next");
    generator["throw"] = invoke.bind(generator, "throw");
    generator["return"] = invoke.bind(generator, "return");

    return generator;
  }

  Gp[iteratorSymbol] = function() {
    return this;
  };

  Gp.toString = function() {
    return "[object Generator]";
  };

  function pushTryEntry(triple) {
    var entry = { tryLoc: triple[0] };

    if (1 in triple) {
      entry.catchLoc = triple[1];
    }

    if (2 in triple) {
      entry.finallyLoc = triple[2];
    }

    this.tryEntries.push(entry);
  }

  function resetTryEntry(entry, i) {
    var record = entry.completion || {};
    record.type = i === 0 ? "normal" : "return";
    delete record.arg;
    entry.completion = record;
  }

  function Context(tryList) {
    // The root entry object (effectively a try statement without a catch
    // or a finally block) gives us a place to store values thrown from
    // locations where there is no enclosing try statement.
    this.tryEntries = [{ tryLoc: "root" }];
    tryList.forEach(pushTryEntry, this);
    this.reset();
  }

  runtime.keys = function(object) {
    var keys = [];
    for (var key in object) {
      keys.push(key);
    }
    keys.reverse();

    // Rather than returning an object with a next method, we keep
    // things simple and return the next function itself.
    return function next() {
      while (keys.length) {
        var key = keys.pop();
        if (key in object) {
          next.value = key;
          next.done = false;
          return next;
        }
      }

      // To avoid creating an additional object, we just hang the .value
      // and .done properties off the next function object itself. This
      // also ensures that the minifier will not anonymize the function.
      next.done = true;
      return next;
    };
  };

  function values(iterable) {
    if (iterable) {
      var iteratorMethod = iterable[iteratorSymbol];
      if (iteratorMethod) {
        return iteratorMethod.call(iterable);
      }

      if (typeof iterable.next === "function") {
        return iterable;
      }

      if (!isNaN(iterable.length)) {
        var i = -1, next = function next() {
          while (++i < iterable.length) {
            if (hasOwn.call(iterable, i)) {
              next.value = iterable[i];
              next.done = false;
              return next;
            }
          }

          next.value = undefined;
          next.done = true;

          return next;
        };

        return next.next = next;
      }
    }

    // Return an iterator with no values.
    return { next: doneResult };
  }
  runtime.values = values;

  function doneResult() {
    return { value: undefined, done: true };
  }

  Context.prototype = {
    constructor: Context,

    reset: function() {
      this.prev = 0;
      this.next = 0;
      this.sent = undefined;
      this.done = false;
      this.delegate = null;

      this.tryEntries.forEach(resetTryEntry);

      // Pre-initialize at least 20 temporary variables to enable hidden
      // class optimizations for simple generators.
      for (var tempIndex = 0, tempName;
           hasOwn.call(this, tempName = "t" + tempIndex) || tempIndex < 20;
           ++tempIndex) {
        this[tempName] = null;
      }
    },

    stop: function() {
      this.done = true;

      var rootEntry = this.tryEntries[0];
      var rootRecord = rootEntry.completion;
      if (rootRecord.type === "throw") {
        throw rootRecord.arg;
      }

      return this.rval;
    },

    dispatchException: function(exception) {
      if (this.done) {
        throw exception;
      }

      var context = this;
      function handle(loc, caught) {
        record.type = "throw";
        record.arg = exception;
        context.next = loc;
        return !!caught;
      }

      for (var i = this.tryEntries.length - 1; i >= 0; --i) {
        var entry = this.tryEntries[i];
        var record = entry.completion;

        if (entry.tryLoc === "root") {
          // Exception thrown outside of any try block that could handle
          // it, so set the completion value of the entire function to
          // throw the exception.
          return handle("end");
        }

        if (entry.tryLoc <= this.prev) {
          var hasCatch = hasOwn.call(entry, "catchLoc");
          var hasFinally = hasOwn.call(entry, "finallyLoc");

          if (hasCatch && hasFinally) {
            if (this.prev < entry.catchLoc) {
              return handle(entry.catchLoc, true);
            } else if (this.prev < entry.finallyLoc) {
              return handle(entry.finallyLoc);
            }

          } else if (hasCatch) {
            if (this.prev < entry.catchLoc) {
              return handle(entry.catchLoc, true);
            }

          } else if (hasFinally) {
            if (this.prev < entry.finallyLoc) {
              return handle(entry.finallyLoc);
            }

          } else {
            throw new Error("try statement without catch or finally");
          }
        }
      }
    },

    _findFinallyEntry: function(finallyLoc) {
      for (var i = this.tryEntries.length - 1; i >= 0; --i) {
        var entry = this.tryEntries[i];
        if (entry.tryLoc <= this.prev &&
            hasOwn.call(entry, "finallyLoc") && (
              entry.finallyLoc === finallyLoc ||
              this.prev < entry.finallyLoc)) {
          return entry;
        }
      }
    },

    abrupt: function(type, arg) {
      var entry = this._findFinallyEntry();
      var record = entry ? entry.completion : {};

      record.type = type;
      record.arg = arg;

      if (entry) {
        this.next = entry.finallyLoc;
      } else {
        this.complete(record);
      }

      return ContinueSentinel;
    },

    complete: function(record) {
      if (record.type === "throw") {
        throw record.arg;
      }

      if (record.type === "break" ||
          record.type === "continue") {
        this.next = record.arg;
      } else if (record.type === "return") {
        this.rval = record.arg;
        this.next = "end";
      }

      return ContinueSentinel;
    },

    finish: function(finallyLoc) {
      var entry = this._findFinallyEntry(finallyLoc);
      return this.complete(entry.completion);
    },

    "catch": function(tryLoc) {
      for (var i = this.tryEntries.length - 1; i >= 0; --i) {
        var entry = this.tryEntries[i];
        if (entry.tryLoc === tryLoc) {
          var record = entry.completion;
          if (record.type === "throw") {
            var thrown = record.arg;
            resetTryEntry(entry, i);
          }
          return thrown;
        }
      }

      // The context.catch method must only be called with a location
      // argument that corresponds to a known catch block.
      throw new Error("illegal catch attempt");
    },

    delegateYield: function(iterable, resultName, nextLoc) {
      this.delegate = {
        iterator: values(iterable),
        resultName: resultName,
        nextLoc: nextLoc
      };

      return ContinueSentinel;
    }
  };
})(
  // Among the various tricks for obtaining a reference to the global
  // object, this seems to be the most reliable technique that does not
  // use indirect eval (which violates Content Security Policy).
  typeof global === "object" ? global :
  typeof window === "object" ? window : this
);


// ===================================

var addGenerator = regeneratorRuntime.mark(function addGenerator() {
  var i;
  return regeneratorRuntime.wrap(function addGenerator$(context$1$0) {
    while (1) switch (context$1$0.prev = context$1$0.next) {
      case 0:
        i = 0;
      case 1:
        if (!true) {
          context$1$0.next = 7;
          break;
        }
        context$1$0.next = 4;
        return i;
      case 4:
        i += context$1$0.sent;
        context$1$0.next = 1;
        break;
      case 7:
      case "end":
        return context$1$0.stop();
    }
  }, addGenerator, this);
});

var adder = addGenerator();
adder.next().value; // 0
adder.next(5).value; // 5
adder.next(5).value; // 10
adder.next(5).value; // 15
adder.next(50).value; // 65