[Haskell-beginners] Re: ghci access to .hs functions

prad prad at towardsfreedom.com
Thu Aug 12 04:42:58 EDT 2010

On Thu, 12 Aug 2010 09:01:42 +0100
Brent Yorgey <byorgey at seas.upenn.edu> wrote:

> Can you show
> us the exact contents of your .hs file?
certainly! but now i take it all back! :(
it's working fine without the return().

it compiles main when i :l or when i ghci the file from the command

so now i think i'm delusional. :D :D

anyway, here's some of the code below and i'll ask another question. in
the function:

-- edFil: edits a file with vim
-- edFil :: String -> IO GHC.IO.Exception.ExitCode (not in scope error) 
edFil kV = rawSystem "vim" ["+source ~/.vim/ftplugin/html/HTML.vim",kV]

i got the type from ghci, but if i actually put it in i get error:
Not in scope: type constructor or class `GHC.IO.Exception.ExitCode'

if i don't do the type definition that ghci gives me, everything
compiles fine.

so i don't understand the type definition, much less what's happening

import System (getArgs)
import System.Cmd (rawSystem)
import Data.List(elemIndices)
import Database.HDBC
import Database.HDBC.PostgreSQL (connectPostgreSQL)

main = do
    args <- getArgs
    let act = head args
    conn <- connectPostgreSQL "host=localhost dbname=lohv user=pradmin"
    case act of 
         "add"  -> do
             kV1 <- dbDef conn
             upDbs conn (fromSql kV1)
             return ()
         "upd"  -> do
             upDbs conn (last args)
             return ()
         "all"  -> do
             gtKys conn
             return ()
         _      -> putStrLn "add, upd num, all only!!" 
    commit conn
    disconnect conn
    putStrLn "All Done!"
    return  ()

-- bkS2L: break a string into a list of strings
--  dC char delimiter; oS original string 
bkS2L :: (Char -> Bool) -> String -> [String]
bkS2L dC [] = []
bkS2L dC oS = let (h,t) = break dC oS
                  in  h : case t of
                               []   -> []
                               _:t  -> bkS2L dC t

-- dbDef: adds a default entry to db
dbDef :: (IConnection conn) => conn -> IO SqlValue
dbDef conn = do
    run conn "INSERT INTO main DEFAULT VALUES" []
    ((r:z):zs) <- quickQuery conn "SELECT last_value from
main_key_seq" [] return r

-- edFil: edits a file with vim
    -- edFil :: String -> IO GHC.IO.Exception.ExitCode (not in scope
edFil kV = rawSystem "vim" ["+source ~/.vim/ftplugin/html/HTML.vim",kV]

-- gtInx: gets indices for each element of substring in string
gtInx :: (Eq a) => [a] -> [a] -> [(a,[Int])]
gtInx hL nL = map (\x -> (x,elemIndices x hL)) nL

-- gtKys: gets all key values in database
gtKys :: (IConnection conn) => conn -> IO [()]
gtKys conn = do
    r <- quickQuery conn "SELECT key from main" []
    let kL = concat $ map (map fromSql) r
    mapM (mkPag conn) kL



there are more functions, but it is all working fine.

In friendship,

                                      ... with you on your journey
Towards Freedom
http://www.towardsfreedom.com (website)
Information, Inspiration, Imagination - truly a site for soaring I's

More information about the Beginners mailing list