On 11 August 2017 at 15:13, Steven D'Aprano <st...@pearwood.info> wrote:
> On Fri, Aug 11, 2017 at 02:34:53PM +1000, Nick Coghlan wrote:
>> This is another good reason why a termination condition would need to
>> be checked before the filter condition rather than either after it, or
>> only when the filter condition was true.
> Why is this a problem that needs solving?

Because the most obvious interpretation of a completely independent
"while" clause in comprehensions would be as a nested loop inside the
outer for loop, not as a nested if-else-break statement.

As a result of that, I'm only personally prepared to support for-while
comprehensions if they're syntactic sugar for a combined statement
level for-while loop that makes it clear why only the "for" clauses in
a comprehension create new loops.

I *wouldn't* be prepared to support them if they could only be
explained in terms of a direct mapping to an if statement and had no
statement level counterpart that actually used the "while" keyword.


Nick Coghlan   |   ncogh...@gmail.com   |   Brisbane, Australia
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