Nils Anders Danielsson
My program is failing with head [], or an array bounds error, or some other random error, and I have no idea how to find the bug. Can you help?
Compile your program with -prof -auto-all (make sure you have the profiling libraries installed), and run it with +RTS -xc -RTS to
I also have experienced - ahem - varying results with -xc. My solution is to use 'ghc -cpp' instead, and something like the following: import Prelude hiding (head,read) /* ugly, but a real functon would block subsequent imports */ #define BUG(C_,M_) (error ("Program error - '"++C_++"' failed: "++M_++". Location: "++__FILE__++" line: "++ show __LINE__)) #define head (\xs -> case xs of { (x:_) -> x ; _ -> BUG("head","empty list")}) #define at (let {at_ (y:_) 0 = y; at_ (y:ys) n = if n>0 then at_ ys (n-1) else BUG("at","negative index"); at_ _ _ = BUG ("at","index too large")} in \a x -> at_ a x) #define read (\s -> case [ x | (x,t) <- reads s, ("","") <- lex t] of { [x] -> x ; [] -> BUG("read","no parse"); _ -> BUG("read","ambigous parse")}) #define fromJust (\x -> case x of Just a -> a; Nothing -> BUG("fromJust","Nothing")) #define undefined (error ("Hit 'undefined' in "++__FILE__++", "++show __LINE__)) This redefines a bunch of "difficult" functions to report file name and line number, instead of just an anonymous error message. It won't work for (infix, non-alpha) operators -- like array indexing -- or identifiers with apostrophes, unfortunately. -k -- If I haven't seen further, it is by standing in the footprints of giants