Vocabulary/atrank

       result of u@:v                                  result of u@v
             ^                                               ^
             |                                               |
             |                                               |
   +-------------------+                                 collect results
   |       apply       |                                 and add fill
   |         u         |                                  ^ ^ ^ ^
   |      on entire    |                                  | | | |  result cells
   |     result of v   |                                  | | | |  of u
   +-------------------+                                  | | | |
             ^                                     +-------------------+
             |                                     |       apply       |
             |                                     |         u         |
          collect                                  |      on each      |
          results                                  |  result cell of v |
          and add                                  +-------------------+
           fill                                           ^ ^ ^ ^
          ^ ^ ^ ^   result cells                          | | | |   result cells
          | | | |   of v                                  | | | |   of v
          | | | |                                         | | | |
 +-----------------------+                       +-----------------------+
 |         apply         |                       |         apply         |
 |           v           |                       |           v           |
 |        on each        |                       |        on each        |
 |          cell         |                       |          cell         |
 +-----------------------+                       +-----------------------+
  ^ ^ ^ ^         ^ ^ ^ ^                         ^ ^ ^ ^         ^ ^ ^ ^
  | | | |         | | | |                         | | | |         | | | |
  | | | |         | | | |                         | | | |         | | | |
  | | | |         | | | |                         | | | |         | | | |
split x into    split y into                    split x into    split y into
   cells           cells                           cells           cells
     ^               ^                               ^               ^
     |               |                               |               |
    [x]              y                              [x]              y