On Mon, Nov 13, 2006 at 12:17:07PM +0000, Simon Peyton-Jones wrote:
The "Maybe.fromJust: Nothing" comes from the library code itself. The "Nat1" part is simply the name of the binary. It give no clue to who called fromJust.
I do not understand the whole idea. First, the same problem is for many functions: head, tail, and others. Also I remember that in some cases GHC reports at run-time something like this: unexhaustive pattern corresponding to the line No ... in the module ... , and this helps a lot. If an error of kind (f _) appears in the GHC library function f, the run-time system, probably recalls who had called for f, because it stores the stack of calls, etc, I do not know ... ?
Finding who called fromJust is an often-requested feature eg tp://hackage.haskell.org/trac/ghc/ticket/960. Currently our best answer to try with the -xc flag (involves recompiling)
The Haskellwiki debugging page could perhaps mention the -xc thing. I had trouble even finding the page from the Haskell.org home page. http://haskell.org/haskellwiki/Debugging
I do not know what is wiki. Is not this sufficient to look into the GHC User Guide for -xc ? So far, I only tried ghc $dmCpOpt -xc --make Nat1 and obtained ghc-6.6: unrecognised flags: -xc Then, tried ./Nat1 +RTS -xc -RTS and obtained not built for: -prof ... So: to re-make all the project for profiling, and then to try ./Nat1 +RTS -pT -xc -RTS ? ----------------- Serge Mechveliani mechvel@botik.ru