[Haskell-beginners] Prelude.(!!): index too large

[Roger Mason]

Hello,

The following fragment compiles but causes a runtime error:

Prelude.(!!): index too large

If I comment out the line 'hPutStr outh ( show ncat)' the program runs 
fine (but there is no output, of course).

Thanks for any help.

Roger

writeOutput infile outfile list fox mw nox ncat units = do
           inh <- openFile infile ReadMode -- the file of analyses, one 
per line
           outh <- openFile outfile WriteMode
           mainloop inh outh list fox mw nox ncat units
           hClose outh
           hClose inh

-- the calculations are here
mainloop inh outh list fox mw nox ncat units = do
              ineof <- hIsEOF inh
              if ineof
                      then do
                          print list      -- For testing/debugging only
                          return ()
                      else do
                    inpStr <- hGetLine inh
                    let list' = inpStr:list
                            let dat = floatData list' -- the analytical 
input data
                            let ta = zipWith (/) dat 
units                            -- convert all to wt%
                            let moles = zipWith (/) ta mw
                            let apo = zipWith (*) nox moles
                            let factor = fox/(sum apo)
                            let nanions= (map (* factor) apo)
                            let catox = zipWith (/) ncat nox
                            let ncat = zipWith (*) catox nanions
                            hPutStr outh ( show ncat)
                    mainloop inh outh list' fox mw nox ncat units

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