1:
I've got another n00b question, thanks for all the help you have been giving me!
I want to read a text file. As an example, let's use /usr/share/dict/words and try to print out the last line of the file. First of all I came up with this program:
import System.IO main = readFile "/usr/share/dict/words" >>= putStrLn.last.lines
This program gives the following error, presumably because there is an ISO-8859-1 character in the dictionary: "Program error: <handle>: IO.getContents: protocol error (invalid character encoding)"
How can I tell the Haskell system that it is to read ISO-8859-1 text rather than UTF-8?
I now used iconv to convert the file to UTF-8 and tried again. This time it worked, but it seems horribly inefficient -- Hugs took 2.8 seconds to read a 96,000 line file. By contrast the equivalent Python program:
print open("words", "r").readlines()[-1]
took 0.05 seconds. I assume I must be doing something wrong here, and somehow causing Haskell to use a particularly inefficient algorithm. Can anyone give me any clues what I should be doing instead?
a) Compile your code with GHC instead of interpreting it. GHC is blazing fast. $ ghc -O A.hs $ time ./a.out Zyzzogeton ./a.out 0.23s user 0.01s system 91% cpu 0.257 total b) If not satisifed with the result, Use packed strings (as python does). http://www.cse.unsw.edu.au/~dons/fps.html import qualified Data.FastPackedString as P import IO main = P.readFile "/usr/share/dict/words" >>= P.hPut stdout . last . P.lines $ ghc -O2 -package fps B.hs $ time ./a.out Zyzzogeton./a.out 0.04s user 0.02s system 86% cpu 0.063 total 0.06s is ok with me :) -- Don