Hi Simon,
Simon Marlow wrote:
If you felt like working on this yourself, possibly with Pepe, then
we'd be happy to support in any way we can.
Thanks. It may happen though it is not probable. I do not know the code
so anything non-trivial is a significant effort and my free weekends and
evenings are sparse :-(
If I would do anything, should it be posted here, sent to Pepe, or
attached to the ticket?
Is it a habit to indicate in the ticket that somebody started coding it
actually (especially if it takes longer to implement)?
So #1531 is tricky to fix, unfortunately. The implementation of
_result is a bit of a hack in the first place. The fundamental
problem is that a tick expression looks like this
case tick<n> of
_ -> e
where 'e' is not necessarily exactly the same as the expression that
was originally inside the tick. We are careful to maintian the
property that the tick is evaluated iff the original expression is
evaluated, but that's all. _result is bound to e, which may or may
not be what you wanted.
One way to fix it would be to add extra constraints on what the
simplifier can do with tick expressions. I don't like the sound of
that because (a) I doni't know exactly what restrictions we'd have to
add and (b) this amounts to changing the semantics of Core (i.e.
changing which transformations are valid).
Ok, I did not understand this part a bit till I did not skim over
http://www.haskell.org/~simonmar/papers/ghci-debug.pdf
Maybe that paper should be mentioned on the wiki pages about debugger.
Something like: "If you do not understand why ghci debugger is limited
in such a strange way read this."
A breakpoint condition on _result:
My guess is that in about half of the cases I can just put them on a
free variable on some other location just as comfortably. In other cases
I'm out of luck :)
As for as /:next/ command:
Like Pepe indicated, I do not have idea how to do it without working
_result and without dynamic stack. Though dynamic stack should not be
that hard since how otherwise could profiler count ticks for cost centers.
And dynamic stack would be great. It would create new options where to
store lists of free variables of selected expressions :)
Maybe there's another way to fix it, but I can't think of one right now.
If by simplifier you did not mean straight translation to core, then I
assume you wanted to try to just skip over all the optimizations
(simplifications?). Was it hard to do it or was the performance impact
so bad that it was not worth the addition of a command line switch?
Thanks for reading the post about debugging, now there is at least a
chance that it will be better once.
Peter.
_______________________________________________
Glasgow-haskell-users mailing list
Glasgow-haskell-users@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
