GHCi debugger status

Claus Reinke claus.reinke at
Mon Nov 24 06:06:03 EST 2008

 >> It is supposed to show only free variables in the selected expression.
>>  I'm sure I had cases when I was able to access variables which were
>>  not free in the selected expression but which would have been in
>>  scope if used in the selected expression. The values available seemed
>>  correct (contrary to your case). I thought it was a step to get all
>>  the variables in scope to be visible but later I learned it is not
>>  feasible and my lucky experience was probably a bug. If I encounter
>>  it again should I fill a bug report? I mean: is it really a bug?

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)

- with only the current expression and some of its free variables
    accessible, I seem to be unable to use the debugger effectively
    (it would be less of a problem if the current expression could
    be displayed in partially reduced source form, instead of partially
    defined value form)

Currently, I only use the debugger rarely, and almost always have 
to switch to trace/etc to pin down what it is hinting at. What is the 
intended usage pattern that makes the debugger more effective/
convenient than trace/etc, and usable without resorting to the latter?


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