Michael Hudson wrote:
> This is, to me, neat and clear. I don't find the idea that iterators
> are tied to exactly 1 for loop an improvement (even though they
> usually will be).
To fix this in a fully backward-compatible way, we
need some way of distinguishing generators that
expect to be finalized.
Suppose we leave the 'yield' statement alone, and
introduce a new statement 'suspend', which alone
has the new capabilities of
(1) allowing injection of exceptions
(2) ability to return a value
(3) permissibility in a try-finally
Doing throw() on a generator that is stopped at
a yield statement would simply raise the exception
without changing the state of the generator. So
the for-loop could be made to finalize by default,
and existing generators would be unaffected.
A with-statement generator would then look like
@with_template
def foo():
initialize()
try:
suspend
finally:
finalize()
which I think looks quite nice, because 'suspend'
seems more suggestive of what is happening when
you're not yielding a value. The same thing applies
to coroutine-type applications.
For partial iteration of new-style generators,
there could be a new statement
for var from expr:
...
or maybe just a wrapper function
for var in partial(expr):
...
--
Greg Ewing, Computer Science Dept, +--------------------------------------+
University of Canterbury, | A citizen of NewZealandCorp, a |
Christchurch, New Zealand | wholly-owned subsidiary of USA Inc. |
[EMAIL PROTECTED] +--------------------------------------+
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