Stephen J. Turnbull wrote:
Lie Ryan writes:
The proposal enables comprehension to become filter+map+filter, map+filter, filter+map, or map-only; eliminating the redundant map in (map+filter)+(map+filter).
The problem with the proposal is that that is *all* it does. I don't see how you plan to disambiguate in cases where the desired operation "really is" (map+filter)+(map+filter). So what you're stuck at is "I want this one operation to be a one-liner." The reply to that is "not every two-line function needs to have special syntax."
The regular map+filter is still available by not using the `as` keyword (or by not calling F). Thus when what you really wanted is two maps, you need to use two comprehensions. The number of maps should == The number of comprehension; currently it is not always possible to do so, when the assumed map and filter ordering doesn't match our required ordering.