Without
From NARS2000


L is a scalar or vector, else signal RANK ERROR.  
R is an arbitrary array.  
Z is a vector identical to (~L∊R)/L.  
The result is sensitive to ⎕CT. 
This feature is implemented by an internal magic function:
∇ Z←L #DydTilde R
[1] Z←(~L∊R)/L
∇