[Yhc] Crashing Queens

[Neil Mitchell]

Hi,

Using the attached program:

--------------------------------------------------------------------------------
D:\Temp>yhc Queens.hs
Compiling Queens           ( Queens.hs )

D:\Temp>yhi Queens.hbc
Assertion failed: pinfo->info.tag == I_PINFO, file d:\sources\yhc\current\src\ru
ntime\bckernel\mutins.h, line 295

This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
--------------------------------------------------------------------------------

This also shows we have assertions on in the release "scons yhi" code,
I guess they can stay in for now, but we really do need an
optimisation mode.

Program from Matt :-)

Thanks

Neil


----------- Queens.hs --------------

module Queens where

main = nsoln 9

len :: [a] -> Int
len [] = 0
len (x:xs) = 1 + len xs

nsoln :: Int -> Int
nsoln nq = len (gen nq)
  where
    gen :: Int -> [[Int]]
    gen 0 = [[]]
    gen n = [ (q:b) | b <- gen (n-1), q <- [1,2,3,4,5,6,7,8,9] {-toOne
nq-}, safe q 1 b]

safe :: Int -> Int -> [Int] -> Bool
safe x d []    = True
safe x d (q:l) = x /= q && x /= q+d && x /= q-d && safe x (d+1) l

toOne :: Int -> [Int]
toOne n = if n == 1 then [1] else n : toOne (n-1)