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

12 Aug 2010

      Hey prad, I was checking out your code and noticed a couple of things
you could be interested to know.

Your main will allways be 'IO ()' , but that doesn't mean you must
sparkle 'return ()' all over the place :P Check this out:

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)
         "upd"  -> upDbs conn (last args)
         "all"  -> gtKys conn
         _      -> putStrLn "add, upd num, all only!!" 
    commit conn
    disconnect conn
    putStrLn "All Done!"

I took the liberty of modifying your gtKys function:

-- gtKys: gets all key values in database [NOTICE mapM_ for mapM]
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

Only if 'upDbs' return some value inside IO you'd replace their calls
for " upDbs conn some >> return () ". Although I assume those statements
are simple 'IO ()', just like 'putStrLn string'

El jue, 12-08-2010 a las 01:42 -0700, prad escribió:
...
On Thu, 12 Aug 2010 09:01:42 +0100
Brent Yorgey  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
line.
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
here.
======
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
error) 
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.

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

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