On 9/18/07, Pepe Iborra
Could you paste a ghci session demonstrating the problem?
Here is a very short and simple debug session showing the problem: ======================================= *Main> :l debug68.hs [1 of 1] Compiling Main ( debug68.hs, interpreted ) Ok, modules loaded: Main. *Main> :break qsort Breakpoint 1 activated at debug68.hs:(1,0)-(3,55) *Main> main Stopped at debug68.hs:(1,0)-(3,55) _result :: [a] = _ [debug68.hs:(1,0)-(3,55)] *Main> :delete * [debug68.hs:(1,0)-(3,55)] *Main> :continue [0,1,3,4,8,11,18,23] *Main> :break qsort Breakpoint 2 activated at debug68.hs:(1,0)-(3,55) *Main> main [0,1,3,4,8,11,18,23] ======================================= The code: ======================================= qsort [] = [] qsort (a:as) = qsort left ++ [a] ++ qsort right where (left,right) = (filter (<=a) as, filter (>a) as) main = do print $ qsort [8, 4, 0, 3, 1, 23, 11, 18] ======================================= The sequence is: 1: set a breakpoint at qsort 2: evaluate function main 3: execution stopped at qsort (as expected) 4: delete all breakpoints 5: set breakpoint at qsort again 6: evaluate function main 7: that lazy haskell show the result without stopping at the breakpoint Just for fun I wrote an IO qsort function: qsortIO :: (Ord a) => [a] -> IO [a] qsortIO [] = return [] qsortIO (a:as) = do l <- qsortIO left r <- qsortIO right return $ l ++ [a] ++ r where (left, right) = (filter (<=a) as, filter (>a) as) and this one gets debugged on each run thanks to it's IO signature. Hope this helps, Best regards, Olivier.