Understanding 'the defaultStack'

[Jeanne A. E. DeVoto]

At 11:23 AM +1100 10/9/2016, Monte Goulding wrote:
>stack A - is defaultStack in its own script
>go stack B
>   stack B preOpenStack - stack B now defaultStack in its own script
>   go stack C
>      stack C preOpenStack - stack C no defaultStack in its own script
>   stack B preOpenStack continues but stack C is now the defaultStack
>back to stack A script and now stack B is the defaultStack
>
>But if you change it to set to the topStack then when you go back to 
>the stack A script then stack C will be the defaultStack.

Hmm. I actually would have expected stack C to still be the 
defaultStack on returning to stack A. defaultStack is a global 
property, theoretically.


>Thinking on this some more I don't think you can do what you are 
>suggesting here. Go currently sets the defaultStack to the target 
>stack if it is topLevel. If it set the defaultStack to the topStack 
>it would depend on the current state of the environment whether the 
>defaultStack is the stack being opened by go after the command while 
>at the moment it just depends on the mode of the stack being opened.

Not sure how that makes it impossible to set it to the topStack...?

(Although I agree with Jacque that there's code out there that relies 
on the current behavior, possibly without the writer even really 
being aware of it.)