[Jprogramming] one element list of an integer to an atom

[Linda Alvord]

   a=:1$3
   a
3
   3= 2 3 5 3 4
0 1 0 1 0
   a= 2 3 5 3 4
|length error
|   a    =2 3 5 3 4
   
   ".a
|domain error
|       ".a
   a+5
8

Clearly, a is numeric. How can I change  a  to a numeric atom  3 , rather
than a one element list  3 ?

I need to find where the 3's are in a list. The result of executing some
expression has produced a one item list of a  3 .

I think I may have known how in APL once upon a time.

Linda