State Indicator

R←⎕SI

R is a nested vector of vectors giving the names of the functions or operators in the execution stack.

      )SI
#.PLUS[2]*
.
#.MATDIV[4]
#.FOO[1]*
⍎

      ⎕SI
 PLUS  MATDIV  FOO

      (⍴⎕LC)=⍴⎕SI
1

If execution stops in a callback function, ⎕DQ will appear on the stack, and may occur more than once

      )SI
#.ERRFN[7]*
⎕DQ
#.CALC
⎕DQ
#.MAIN

To edit the function on the top of the stack:

      ⎕ED ⊃⎕SI

The name of the function which called this one:

      ⊃1↓⎕SI

To check if the function ∆N is pendent:

     ((⊂∆N)∊1↓⎕SI)/'Warning : ',∆N,' is pendent'