Dyalog Forums

Not able to understand the behaviour of ⎕SI and ⎕STACK in defined functions.

I prepared the following:

      ⍝
TOPFN←{
     ⎕←'§§§§§§§§§§§§§§'
     ⎕←'⎕SI at level 0:',⎕SI
     ⎕←'⍴⎕LC:',(⍴⎕LC),'   ⊃⍴⎕STACK:',⊃⍴⎕STACK
     ⎕←⎕STACK
     CALLED1←{
         ⎕←'§§§§§§§§§§§§§§'
         ⎕←'⎕SI at level 1:',⎕SI
         ⎕←'⍴⎕LC:',(⍴⎕LC),'   ⊃⍴⎕STACK:',⊃⍴⎕STACK
         ⎕←⎕STACK
         CALLED2←{
             ⎕←'§§§§§§§§§§§§§§'
             ⎕←'⎕SI at level 2:',⎕SI
             ⎕←'⍴⎕LC:',(⍴⎕LC),'   ⊃⍴⎕STACK:',⊃⍴⎕STACK
             ⎕←⎕STACK
             ⍵
         }
         CALLED2 ⍵
     }
     CALLED1 ⍵ 
 }

and executed
TOPFN ''

The result is (Dyalog 13/Classic 32):

      ⍝
§§§§§§§§§§§§§§
⎕SI at level 0: TOPFN 
⍴⎕LC: 1    ⊃⍴⎕STACK: 2
 ∇TOPFN  
        *
§§§§§§§§§§§§§§
⎕SI at level 1: TOPFN 
⍴⎕LC: 1    ⊃⍴⎕STACK: 3
 ∇CALLED1  
 ∇TOPFN    
          *
§§§§§§§§§§§§§§
⎕SI at level 2: TOPFN 
⍴⎕LC: 1    ⊃⍴⎕STACK: 4
 ∇CALLED2  
 ∇CALLED1  
 ∇TOPFN    
          *

Here the state indicator stack looks like correct, the state indicator is not aligned.
Please note that the function CALLED2 is local to CALLED1.

Thank you for help.

This is a bug in ⎕STACK, which has not been made Dfn-aware.

In your example CALLED1 and CALLED2 are both tail calls and so should not show an increase in the size of the state indicator. In fact, internally, for a lexically-inward tail call, a vestigial stack frame is retained until the lexical level ({} nesting depth) drops, when it is removed.

The bug is that the code for ⎕SI and ⎕LC has been amended to ignore these "invisible" stack frames but the code for ⎕STACK hasn't yet.

Here is a simple repro:

      {{⍬∘⍴∘⍴¨⎕lc ⎕si ⎕stack}⍵}0    ⍝ should return 1 1 1
1 1 2

I have logged this as a bug, ref[7766].

JohnS|Dyalog wrote:

      Here is a simple repro:

      {{⍬∘⍴∘⍴¨⎕lc ⎕si ⎕stack}⍵}0    ⍝ should return 1 1 1
 1 1 2

I think that 1 1 2 is correct.
In fact ⎕STACK must contain a second row related to "desk calculator level".

Do I miss something?