[Haskell-beginners] ghci reports "The last statement in a 'do'
construct must be an expression" error
Nico Rolle
nico.rolle at googlemail.com
Wed Jun 17 12:13:03 EDT 2009
it really was an indentation error
i configured my editor to expand tabs into spaces but somehow he did a real
tab on line 9 and 10
thank you
2009/6/16 Daniel Fischer <daniel.is.fischer at web.de>
> Am Dienstag 16 Juni 2009 22:35:17 schrieb Nico Rolle:
> > Hi
> >
> > Heres my code snippet.
> > It reports that my error is in line 9 right after the main definition.
> > All functions that i call work under normal circumstances.
> > Thanks
>
> Must be the indentation, probably the xs is indented further than the
> following line
> (though that's not the case for the code copy-pasted from the mail to an
> editor).
>
> But note that this will most likely print out 0 twice.
> The let pnp = ... bindings don't cause any computation to occur.
> To measure the time the computations take, you must force them to occur
> between the two
> calls to getCurrentTime.
>
> >
> >
> > module Benchmark
> > where
> >
> > import ReadCSV
> > import Operators
> > import Data.Time.Clock (diffUTCTime, getCurrentTime)
> >
> > main = do
> > xs <- readCSV "dataconvert/lineitem.tbl" '|'
> > start <- getCurrentTime
> > let pnp = projection [5] xs
> > let snp = selection (\x -> (x!!0) > (Int 17000)) pnp
> > end <- getCurrentTime
> > putStrLn $ show (end `diffUTCTime` start)
> > start2 <- getCurrentTime
> > let pp = pProjection [5] xs
> > let sp = pSelection (\x -> (x!!0) > (Int 17000)) pp
> > end2 <- getCurrentTime
> > putStrLn $ show (end2 `diffUTCTime` start2)
> > return xs
>
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