Please comment on PEP XXX: Enhanced Generators

[Paul Rubin]

Oren Tirosh <oren-py-l at hishome.net> writes:
> > 2.  Generator comprehensions:  [yield int(x) for x in floatgen()]
> 
> The only problem I see with this syntax is that the square brackets are
> misleading - the resulting object is not a list.  How about using parens
> instead?  They are not strictly required, but just like for tuples, they
> help disambiguate the syntax.

Actually there's sort of a worse problem with either version, which is
how it interacts with the proposal that yield can return a value.

If I can say "x = yield 3", then can't I say

  x = [yield 3, yield 4, yield 5]
  
which should suspend execution 3 times before actually assigning to x?

And if I can do that, can't I say the same thing as a list (not
generator!) comprehension

  x = [yield i for i in range(3,5)]

I realize that in the original proposal, yield can't necessarily take
an arbitrary argument when it returns a value sent by .submit(), but
the option of doing that (to have fully general coroutines) should be
left open.