On 11/20/11 3:14 PM, Edward Z. Yang wrote:
Here is perhaps one alternate way to frame the documentation:
Rule (1) applies to first-order functions (they take the value directly) Rule (2) applies to higher-order functions (they take functions which generate the value)
I think the appeal of only specifying (2) is that it is *consistent*, though perhaps not in the way someone who hasn't thought too carefully about the issue would immediately assume. I admit, I do fear that there exist some higher order functions for which we really don't want (1) to apply, but fortunately, it's easier to work around being overly strict than being overly lazy.
If we had (1) apply only to first-order functions, then that would address the expressivity concerns I mentioned in the other reply. So I'm all for (1) in the first-order case; which is, as Edward says, just a degenerate version of (2). However, unless someone can (a) demonstrate efficiency reasons for applying (1) in the higher-order case, or (b) demonstrate another way of constructing semilazy operations, I'd prefer that (1) does not apply to the higher-order case in any way other than is required by (2). -- Live well, ~wren