On 10 April 2011 02:24, Raul Miller <[email protected]> wrote: > But being uncertain implies some doubt about what the meaning could > be, and I am not seeing any non-trivial basis for doubt here.
Well, u/y, for 1=#y, could be imagined to be an erroneous expression. Or, it could be the Indeterminate value. What's wrong with that interpretation? But I stress again -- all these are only speculations, and there would be no room for them if the definition itself was unequivocal. > But... the dictionary says: > u/y applies the dyad u between the items of y > > u is - > y is 3 5 9 2 > > It seems to me that if you insert - between the items of 3 5 9 2 you > get 3-5-9-2 That again is plausible but not certain, as it seems to me. `Applies between' does not specify order; it could still be ((3-5)-9)-2 -- as it is in K, by the way -- despite K also evaluating, in general, in a righ-to-left order. I would have no doubt if the definition said, e.g., `u/y, for y = y1 ... yn and n>1, is equivalent to the expression y1 u y2 u ... u yn'. >> Does +/'z' not read as `summing up a string' -- which is what I mean >> by `meaningless'? > >You could read it that way, though 'z' is a character, for the usual >meaning of a string, you would want ,'z' (a string has a length -- in >other word's it's a rank 1 array of characters). Ok, but u/ does not actually discriminate between 'z' and ,'z'. Expressions such as +/'z' (summing up a character) or +/,'z' (summing up a string) seem equally meaningless. >But although +/ can be thought of as sum, it's also reasonable to >think of it as "plus insert", and there may be other reasonable ways >to conceptualize the operation (depending on the domain). For >example, if the domain is arrays consisting only of zeros and >infinities, +/ could be thought of as a boolean reduction. What I am drawing attention is that in u/y, for whatever u and 1=#y, u is totally irrelevant, be it +, *, %: or anything else. Which, in turn, makes expressions like +/'z' or +/1 3$'abc' strangely acceptable. What for would I need them? I really see this as one of the several anomalies in the definition of /. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
