domenic at domenicdenicola.com (2013-09-18T18:53:25.631Z)
On Sep 6, 2013, at 11:18 AM, Brendan Eich wrote:
> There would be no explicit `yield` in the second example, though. (`yield` is an error in any arrow body.)
why no `yield`? Note that I wrote a { } body for the generator arrow function body, rather than an expression body and that generator functions use explicit |yield| in their bodies.
Also, if the expression body form had an implicit `yield` in front of the expression (eg, `c *=> 42`, implicitly yields `42`) then then there would be confusion between
```js
c => (for (p of c) if (p in this) this[p]) //function that returns a generator that yields this[p]
c *=> (for (p of c) if (p in this) this[p]) //function that returns a generator that yields a generator
```
The first form would almost always be what somebody would want.
> I'm not seriously advocating generator arrow function syntax, mind you!
Yup, I think we're better off without them.
On Sep 6, 2013, at 11:18 AM, Brendan Eich wrote: >> Allen Wirfs-Brock <mailto:allen at wirfs-brock.com> >> September 6, 2013 11:01 AM >> >> Almost as good, a arrow function with a generator comprehension as its expression body. For example, a factory for a generator with a lexical this binding: >> >> c => (for (p of c) if (p in this) this[p]) >> >> not much different from a hypothetical generator arrow function and arguably better : >> c *=> {for (p of c) if (p in this) yield this[p]} > > There would be no explicit |yield| in the second example, though. (|yield| is an error in any arrow body.) why no |yield|? Note that I wrote a { } body for the generator arrow function body, rather than an expression body and that generator functions use explicit |yield| in their bodies. Also, if the expression body form had an implicit |yield| in front of the expression (eg, c *=> 42, implicitly yields 42) then then there would be confusion between c => (for (p of c) if (p in this) this[p]) //function that returns a generator that yields this[p] c *=> (for (p of c) if (p in this) this[p]) //function that returns a generator that yields a generator The first form would almost always be what somebody would want. > > I'm not seriously advocating generator arrow function syntax, mind you! Yup, I think we're better off without them. Allen