Retrieving generator references

[Dmitry Soshnikov]

On Sat, Nov 22, 2014 at 8:03 PM, Brendan Eich <brendan at mozilla.org> wrote:

> Axel Rauschmayer wrote:
>>
>>
>> A result of this mixing of concerns is that using `next()` to start a
>> generator feels slightly off and that the argument of that first `next()`
>> invocation is completely ignored.
>>
>
> We've discussed a special generator head form to declare that name, but
> not for ES6. For now it's Pythonic, except we decided not to throw if the
> initial .next call passes a non-undefined value.
>
>
Yeah, in Python world (where initial JS generators came from) a technique
to "prime" a generator is often done via a decorator. JS doesn't have
decorators (yet), but it looks like:

```
// A helper decorator that primes the gen.
function coroutine(func) {
  return (...args) => {
    var gen;
    gen = func(...args);
    gen.next();
    return gen;
  };
}

// Actual gen.
let grep = coroutine(pattern => {
  let line;
  console.log('Looking for ' + pattern);
  while (true) {
    line = yield;
    if (line.indexOf(pattern !== -1)) {
      console.log('Found ' + pattern + ' in ' + line);
    }
  }
  return true;
});

// Usage.
let g = grep('Coffee');

g.send('JavaScript');
g.send('CoffeeScript');
```

In Python it would be used as:

```
@coroutine
def grep(pattern):
  ...
```

Dmitry
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