Y must be a numeric array. R is numeric. R is the reciprocal of Y; that is 1÷Y. If ⎕DIV=0, ÷0 results in a DOMAIN ERROR. If ⎕DIV=1, ÷0 returns 0.
⎕DIV is an implicit argument of Reciprocal.
÷4 2 5 0.25 0.5 0.2 ÷0j1 0j¯1 2j2 4j4 0J¯1 0J1 0.25J¯0.25 0.125J¯0.125 ⎕DIV←1 ÷0 0.5 0 2