For a scalar function such as Power (`*`

) there are three obvious ways it can apply to an array argument:

2 * ⍳6 ⍝ Some powers of 2 1 2 4 8 16 32 (⍳6) * 2 ⍝ Some squares 0 1 4 9 16 25 (⍳6) * ⍳6 ⍝ Some self-exponents 1 1 4 27 256 3125

If there's a scalar argument, it *has* to be used in every function invocation, since there's nowhere else to take arguments from. Rank applies the same principle to arguments with only one cell.