On Tue, Feb 05, 2008 at 06:00:38PM -0600, John Lato wrote:
-- let ary_max = foldl1' max $ elems $ unsafeFreeze myArray
If you use a boxed array type (IOArray or STArray) for myArray, and compiled with GHC, no copying is necessary (you may need to use type annotations to guarantee this). Then use the foldl' function to get array_max, and map it onto the original mutable array. I think it would be safe provided that you calculate ary_max before you start to modify the array, which is true for normalization.
Eek! unsafeFreeze isn't a type cast, it actually modifies flags in the heap object which are used by the generational garbage collector. It's quite concievable that you could get segfaults by modifying a boxed array after passing it to unsafeFreeze. This, I believe, would work: let ary_max = foldl1' max [ inlinePerformIO (readArray myArray ix) | ix <- range (inlinePerformIO (getBounds myArray)) ] But it's equally untested. Stefan