19 Apr
2007
19 Apr
'07
3:10 p.m.
Thanks a lot for the feedback !
On 19/04/2007, at 15:59, Simon Marlow wrote:
> Thanks Alexey. I'm working on ironing out all the wrinkles at the
> moment. Some of the things you point out, like the prompt, are
> already on my ToDo list, and some others I didn't know about, but
> I'll look into them all in due course.
>
> Cheers,
> Simon
>
> Alexey Rodriguez Yakushev wrote:
>> Yesterday I darcs-got the GHC HEAD to play with the debugger and I
>> have the following impressions/bug/suggestions:
>> * I would like to know whether I am debugging mode (i.e. in a
>> breakpoint) or not. For example
>> > *Main> -- normal prompt
>> and, for example,
>> > *Main:[1] > -- in breakpoint 1
>> now, if I evaluate expression "e" via "seq e ()" and it happens to
>> trigger breakpoint 2, I would like to see something like
>> > *Main:[1]:[2] >
>> or some better notation, but you get my point.
>> * The notation for printing a list is non-Haskell, consider the
>> following evaluated head but unevaluated tail:
>> > *Main> :print xs
>> > xs = [True | (_t2::[Bool])]
>> I would have expected "True : (_t2::[Bool])"
I'm working mostly on :print now, while Simon and Bernie work on
breakpoints.
As agreed in #haskell, the pretty printer will be haskellized
promptly, and all Prolog traces will be eliminated :)
>> * Consider the following code:
>> > mymap f [] = []
>> > mymap f (x:xs) = f x:mymap f xs
>> >
>> > main = mapM_ putStrLn $ mymap ('a':) ["hello","bye"]
>> First, I set a breakpoint on line two. When I invoke "main", the
>> breakpoint is triggered two times before "main" is done
>> evaluating. Afterwards, If I type "main" at the ghci prompt again,
>> the breakpoint is not triggered anymore! Even though ":show
>> breaks" lists it.
>> * Again considering the code above, if I break at line 2:
>> > Stopped at FreeVar2.hs:2:17-19
>> > x :: GHC.Base.Unknown
>> > f :: t -> a
>> > xs :: [GHC.Base.Unknown]
>> Now I type "f" and the following message appears:
>> > *** Exception: No match in record selector Var.tcTyVarDetails
In this case the debugger does cannot know what the type of t is.
We still need a good plan for functions. But I totally agree it
shouldn't fail like that.
>> * I was wondering whether it would be nice to have a "break"
>> function/primitive, so that you can write:
>> > mymap f [] = []
>> > mymap f (x:xs) = (break (f x):mymap f xs)
>> with "break" having type "a -> a" and inserting a breakpoint
>> around the argument expression. It is handy to not have to
>> recalculate lines. However I am not so sure anymore. Using line
>> numbers is not as bad as I thought.
>> The debugger is a nice addition to GHC, and I look forward to the
>> debugger being integrated into the Emacs Haskell mode!
Take a look at Shim[1]. The debugger integration will be there soon
(well, sooner or later).
[1] http://shim.haskellco.de
Cheers
pepe