[racket-dev] Short-circuiting comprehensions

My $0.02: I find #:while and #:when to be too close, and #:until and
#:unless even closer.

Robby

On Fri, Sep 14, 2012 at 2:30 PM, Eli Barzilay <eli at barzilay.org> wrote:
> 5 hours ago, Carl Eastlund wrote:
>>
>> Has this been brought up before?  I can't recall.  Does anyone else
>> run into the same issue?
>
> (I think that I brought this up when the comprehensions were first
> discussed, pointing at the similar tool I have in Swindle which makes
> implementing them very easy.)
>
>
> Four hours ago, Matthew Flatt wrote:
>>
>> Also, I think the names `#:while' and `#:until' are too close to
>> `#:when' and `#:unless'. I suggest `#:break-when' and `#:break-unless'.
>> Compare:
>>
>>  > (for*/list ([j 2] [i 10] #:when (i . < . 5)) i)
>>  '(0 1 2 3 4 0 1 2 3 4)
>>  > (for*/list ([j 2] [i 10] #:break-unless (i . < . 5)) i)
>>  '(0 1 2 3 4)
>>
>> I imagine that `#:break-when' and `#:break-unless' are allowed among
>> the clauses much like `#:when' and `#:unless', but also allowed at the
>> end of the body. Is that what you had in mind?
>
> Sorry for the bike-shedding, but to me that `#:break-unless' is even
> harder to read than `#:until'.  Possible explanation: "break unless"
> makes me parse two words and figure out how they combine, and "while"
> is something that I know without doing so.
>
> Another point to consider in favor of `#:while' and `#:until' is that
> they're extremely common names, so they're unlikely to be *that*
> problematic.
>
> (I intentionally left the typo in the first sentence as a
> demonstration of how it's confusing to read...)
>
>
> A different point is that maybe there should also be a `while' and
> `until' looping constructs in the language?  (Whatever they're
> called.)  Every once in a while (ahem) I want that when I write:
>
>   (let loop ()
>      (when (more-work-to-do)
>        (work!)))
>
> And it looks like this:
>
>   (for (#:while (more-work-to-do))
>     (work!))
>
> would not work in the same way that (for () (work!)) doesn't loop
> forever(?).
>
> --
>           ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
>                     http://barzilay.org/                   Maze is Life!
>
> _________________________
>   Racket Developers list:
>   http://lists.racket-lang.org/dev