On Jan 17, 2012, at 10:14 AM, Grant Husbands wrote:
> Allen Wirfs-Brock wrote:
>> do: arr.alternate ({|o| if (...) continue; if (...) break; ...}, {|o| if
>> (...) continue; ...});
>>
>> I don't see how this can support the most likely intended semantics
>
> I think others might have better answers, but it seems that the
> meaning of 'break' is to stop the whole statement, and the meaning of
> 'continue' is to skip the inner block and hence return to
> arr.alternate. I'm sorry for my woolly language, but it seems
> relatively equivalent to a for loop, in which 'break' stops the whole
> statement and 'continue' skips the inner block and hence returns to
> the looping code.
Yes, that was the intended meaning I was trying to express. But what I was
illustrating was that for this to work a continue wihout a target label and an
equivalently located break without a target label need to unwind to different
points in the enclosing nesting structure. This seems different (perhaps
surprisingly so) from equivalent continue/breaks nested only within blocks and
an IterationStatement. But that is the semantics that are need to fulfill my
intent is this particular case. Maybe this generalizes to all use reasonable
cases, but it something about it makes me feel a bit uncomfortable.
>
> Perhaps what I'm saying is that I think "do:" is a label for the whole
> callexpression, covering all lambda-block parameters. As far as the
> specification goes, a continue that 'hits' the block lambda may well
> be best described as a local return.
Yes, this seems about right. But can this behavior for break/continue be
explained in a way that doesn't seems arbitrarily different from
break/continue in the context of IterationStatements and regular blocks.
Perhaps we can describe a general transformation that converts an
IterationStatement to/from an equivalent call to an iteration function with
block lambda arguments.
Allen
>
> Or I might be misreading.
>
> Regards,
> Grant Husbands.
>
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