R is a nested vector of character vectors containing the names of the spaces from which functions in the state indicator were called (⍴⎕NSI←→⍴⎕RSI←→⍴⎕SI).

⎕RSI and ⎕NSI are identical except that ⎕RSI returns refs to the spaces whereas ⎕NSI returns their names. Put another way: ⎕NSI←→⍕¨⎕RSI.

Note that ⎕NSI contains the names of spaces from which functions were called not those in which they are currently running.

      )OBJECTS
xx      yy
 
      ⎕VR 'yy.foo'
     ∇ r←foo
[1]    r←⎕SE.goo
     ∇                          
      ⎕VR'⎕SE.goo'
     ∇ r←goo
[1]    r←⎕SI,[1.5]⎕NSI
     ∇
 
      )CS xx
#.xx
      calling←#.yy.foo
      ]display calling
┌→─────────────┐
↓ ┌→──┐ ┌→───┐ │
│ │goo│ │#.yy│ │
│ └───┘ └────┘ │
│ ┌→──┐ ┌→───┐ │
│ │foo│ │#.xx│ │
│ └───┘ └────┘ │
└∊─────────────┘