In the thread on /\ I wrote that, in my opinion, the Dictionary is unclear as to what u/y returns when 1=#y. Several people responded that, as u must apply between items of y, when there is only one item -- so there is no `between' -- the result is that item.
Surely, this is how we all understand and use /, but my point is that we do so by plausible guessing. The said interpretation is intuitive, and of course the J implementation confirms it, but it is still guessing; it does not follow formally from the Dictionary text. Similarly, how do we know that u/y applies u from right to left along the list? As the Insert article of the Dictionary says nothing explicitly, it is again plausible guessing. I do appreciate the pursuit of concision, but am not always happy with the result. I value clarity more than laconism. This is just my impression of what I read. Other people's may be different. Further on, compared to Haskell's folds or other similar functions, the definition (or behaviour) of u/y seems anomalous in two ways. First, u has actual relevance for 1<#y and 0=#y but not for 1=#y, which is in between. Second, for 1=#y, u is *really* irrelevant, to the effect that, e.g., +/'z' -- a meaningless expression -- has a definite value, 'z', and consequently so do +/\'z' and +/\.'z'. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
