On Aug 31, 2013, at 3:19 PM, Brendan Eich wrote: > Brian Kardell wrote: >> >> Fwiw, just bikesheddingly speaking I actually prefer the *. >> > > Let's review. Three reasons for function* syntax: > > 1. Opt-in required for backward-incompatible definition of 'yield' as > low-precedence unary prefix operator. > > 2. Zero-yield (no yield in body) basis case, useful for delegation via yield* > from another generator. > > 3. Decorator to alert the reader that the body contains yield (ignoring 2 for > a moment) reason. > > You are "bikesheddingly" supporting 3, I take it. Can you say more about why > you want a decorator for human readers? Again ignoring 2, which makes the > case based on what the JS engine must see, a more "objective" criterion in > this case (and, in a different light, in case 1).
I think there is more to #3. The body of a GeneratorFunction has quite different semantics than that of a regular function. This is particularly clear when you think about GFs as actually being constructors/factories. The body of a normal constructor/factory defines what happens before a new instance object is returned to a caller. The body of a GeneratorFunction defines the future behavior of the instance object that is returned to the caller. A regular Function's body is evaluated before it's call returns. A GeneratorFunction's body is evaluated sometime after its call returns. This is a critical difference that must to known to a code reader in order to understand any code that includes a GeneratorFunction definition and is more that sufficient to warrant the * sigil. Personally, I would prefer an even stronger marker, such as a different keyword, but * is adequate. Programming language need to be designed for people. Inferring which functions are GeneratorFunctio n by the presences of yield may be fine for compilers but it isn't good enough for human readers or writiers. Allen _______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
