Thanks. I've realized that as soon as I was in my bed. ;-) Nevertheless, a question comes to me - shouldn't compiler report a warning? I know it cannot in the current state, but it should. :-) Quite dummy C compilers tell me I'm "loosing significant digits of number literals" if I'm doing that. Maybe, already seen in some other thread some time ago, the compiler should be less general/should know more about data types... Thanks and regards Dusan Don Stewart wrote:
kolar:
Hello all,
Maybe there is something obvious I can't see, but I have this behavior for 6.8.2 ghci:
$ghci ttest1p.hs GHCi, version 6.8.2: http://www.haskell.org/ghc/ :? for help Loading package base ... linking ... done. [1 of 1] Compiling Main ( ttest1p.hs, interpreted ) Ok, modules loaded: Main. *Main> encode' [1..100] Loading package array-0.1.0.0 ... linking ... done. Loading package bytestring-0.9.0.1 ... linking ... done. [1,0,2,0,3,0,4,0,5,0,6,0,7,0,8,0,9,0,10,0,11,0,12,0,13,0,... // deleted *Main> B.pack [0..100] "\NUL\SOH\STX\ETX\EOT\ENQ\ACK\a\b\t\n\v\f\r\SO\SI\DLE\DC1\DC2\DC3\DC4\NAK\SYN\ETB\CAN\EM\SUB\ESC\FS\GS\RS\US !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcd" *Main> B.pack $ encode' [1..100] "*** Exception: divide by zero
where ttest1p.hs:
import qualified Data.ByteString as B
encode' [] = [] encode' (x:xs) = if x==0 then 0:0:encode' xs else (x `mod` 256) : (x `div` 256) : encode' xs
What is the difference, except list length and value structure? Where is my error?
ByteStrings take Word8 values as input, so x `div` 256 , where 256 :: Word8, overflows to 0.
-- Don
-- Dusan Kolar tel: +420 54 114 1238 UIFS FIT VUT Brno fax: +420 54 114 1270 Bozetechova 2 e-mail: kolar@fit.vutbr.cz Brno 612 66 Czech Republic --