GHCi debugger status

Pepe Iborra mnislaih at
Mon Nov 24 09:29:56 EST 2008

On Mon, Nov 24, 2008 at 2:03 PM, Peter Hercek <phercek at> wrote:
> Simon Marlow wrote:
>> Claus Reinke wrote:
>>> Perhaps someone could help me to understand how the debugger is supposed
>>> to be used, as I tend to have this problem, too:
>>> - when I'm at a break point, I'd really like to see the current scope
>>>   or, if that is too expensive, the next enclosing scope, in full
>>>   (not only would that tell me what instantiation of my code I'm in,
>>>   it would also seem necessary if I want to reconstruct what the
>>>   current expression is)
>> I don't understand what you mean here - surely in order to "reconstruct
>> what the current expression is" you only need to know the values of the free
>> variables of that expression?  Also I don't understand what you mean by the
>> "next enclosing scope".  Could you give an example?
> Maybe what Claus means is that he would like to see the dynamic
>  stack and be able to traverse it and at each location in the
>  dynamic stack he could investigate the free variables in the
>  expression (corresponding to the dynamic stack slot). I actually
>  considered this as a feature request but I decided that I would
>  like to have this implemented sooner:

As long as you start with :trace, you can see the dynamic stack with
:history, and traverse it with :back.
At any point in the stack the free variables are available, or so I believe.
What is the missing feature you would like to request in this case?

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