queued GHCi commands are not context specific; a bug?

Peter Hercek phercek at gmail.com
Wed Feb 25 13:19:54 EST 2009

Hi GHCi users,

The example is at the end of this email.
I think it is a bug that the second part (:continue) of the command 
`:cmd return "rv\n:continue"' is executed in a different context than 
the first part (rv (request for the value of rv variable)). Notice that 
we did not stop at breakpoint 1 (line 7). Well, the stop happened but it 
continued immediately because of queued :continue command. But the 
command was queued in the context of breakpoint 0 and not breakpoint 1.
Is it a feature or a bug?
If it is a feature it is not good for scripting breakpoints :-/ ... and 
I do not see an easy way to work around it.


PS: I owe responses to some of you on this list, but I must check some 
docs or do some tests first so I hope I'll answer during weekend at worst.

*status:0 peter at metod [716] ~/tmp
%* grep -n '^' b.hs
1:fn :: Int -> Int
2:fn x =
3:  let rv = add x 1 in
4:  rv
6:add :: Int -> Int -> Int
7:add a b = a + b
*status:0 peter at metod [717] ~/tmp
%* ghci b.hs       
GHCi, version 6.10.1: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling Main             ( b.hs, interpreted )
Ok, modules loaded: Main.
*Main> :set stop :list
*Main> :break 4
Breakpoint 0 activated at b.hs:4:2-3
*Main> :break 7
Breakpoint 1 activated at b.hs:7:0-14
*Main> fn 100
Stopped at b.hs:4:2-3
_result :: Int = _
rv :: Int = _
3    let rv = add x 1 in
4    *rv*
[b.hs:4:2-3] *Main> :cmd return "rv\n:continue"
Stopped at b.hs:7:0-14
_result :: Int = _
6  add :: Int -> Int -> Int
7  *add a b = a + b*
[b.hs:4:2-3] *Main> :continue
*Main> :q
Leaving GHCi.
*status:0 peter at metod [718] ~/tmp
% *

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