On Tue, Nov 14, 2006 at 05:28:22PM +0000, Simon Peyton-Jones wrote:
Both of these messages (from Neil and Serge) suggest use debugging ideas. Would anyone like to add them to http://haskell.org/haskellwiki/Debugging [..]
How can I put it there? It needs login. I do not know, whether my idea worths it, but, for any occasion, here is its new formulation ----------------------------------------------------------- Maybe, the simplest way to provide locating in the source code a mismatch run-time error in the library functions head, tail, fromJust, and such, is to avoid these functions and to use explicit matching instead. For example, for the program g x = h $ fromJust $ f x, ghc-6.6 often looses the reference to g, f, and h in its run-time error report -- when f returns Nothing. But for the program g x = let Just y = f x in h y, the ghc run-time report is like this: Main: M1.hs:9:11-22: Irrefutable pattern failed for pattern Data.Maybe.Just y -- it points to the source line! ---------------------------------------------------------------------- ----------------- Serge Mechveliani mechvel@botik.ru