R is a vector of refs to the spaces from which functions in the state indicator were called (⍴⎕RSI←→⍴⎕NSI←→⍴⎕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 ⎕RSI returns refs to the 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]⎕RSI ∇ )CS xx #.xx calling←#.yy.foo ]display calling ┌→───────────┐ ↓ ┌→──┐ │ │ │goo│ #.yy │ │ └───┘ │ │ ┌→──┐ │ │ │foo│ #.xx │ │ └───┘ │ └∊───────────┘