Function assignment           Fn

   sum =. +/
   sum
+-+-+
|+|/|
+-+-+

   a =. i. 10
   a
0 1 2 3 4 5 6 7 8 9
   +/ a
45
   sum a
45
   sum \ a
0 1 3 6 10 15 21 28 36 45

   avg =. sum % #
   avg a
4.5

