scalar =: 10
   vector =: 2 3 5
   matrix =: 3 3 $    7 11 13  17 19 23  29 31 37

   scalar * scalar
100
   scalar * vector
20 30 50
   scalar * matrix
 70 110 130
170 190 230
290 310 370

   vector * vector
4 9 25
   vector * matrix
 14  22  26
 51  57  69
145 155 185

   matrix * matrix
 49 121  169
289 361  529
841 961 1369