f may be any dyadic function that returns a result. Y may be any array whose items in the sub-arrays along the Kth axis are appropriate to the function f.
The axis specification is optional. If present, K must identify an axis of Y. If absent, the last axis of Y is implied. The form R←f⍀Y implies the first axis of Y.
R is an array formed by successive reductions along the Kth axis of Y. If V is a typical vector taken from the Kth axis of Y, then the Ith element of the result is determined as f/I↑V.
The shape of R is the same as the shape of Y. If Y is an empty array, then R is the same empty array.
Examples
∨\0 0 1 0 0 1 0 0 0 1 1 1 1 1 ^\1 1 1 0 1 1 1 1 1 1 0 0 0 0 +\1 2 3 4 5 1 3 6 10 15 +\(1 2 3)(4 5 6)(7 8 9) 1 2 3 5 7 9 12 15 18
M 1 2 3 4 5 6 +\M 1 3 6 4 9 15 +⍀M 1 2 3 5 7 9 +\[1]M 1 2 3 5 7 9 ,\'ABC' A AB ABC T←'ONE(TWO) BOOK(S)' ≠\T∊'()' 0 0 0 1 1 1 1 0 0 0 0 0 0 1 1 0 ((T∊'()')⍱≠\T∊'()')/T ONE BOOK