[Haskell-cafe] Help me TH code.

Serguey Zefirov sergueyz at gmail.com
Wed Oct 27 04:53:53 EDT 2010

2010/10/27 Andy Stewart <lazycat.manatee at gmail.com>:
> Serguey Zefirov <sergueyz at gmail.com> writes:
>> I think that you should use TH properly, without compiler and logical errors.
>> What actually do you want?
> I'm build multi-processes communication program.

You don't need TH here, I think.

You can write a class Ask:

class Ask a where ask :: YourMonad a

and then instance it:

instance Ask Int where ask = liftIO $ do { putStrLn "Enter integer:";
l <- getLine; return $ read l}
instance Ask Char where ask = liftIO $ do { putStrLn "Enter char:"; l
<- getLine; return $ head l}
instance Ask String where ask = liftIO $ do { putStrLn "Enter
string:"; l <- getLine; return l}
instance (Ask a, Ask b, Ask c) => Ask (a,b,c) where ask = liftIO $ do
{ a <- ask; b <- ask; c <- ask; return (a,b,c)}

You can pass ask values between processes, receiving results of asking.

TH is great and good, but it is that only when you absolutely
exhausted of usual Haskell options.

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