[Haskell-cafe] Database.postgreSQL.Simple - ambigious type

[Tom Ellis]

On Sat, Aug 17, 2013 at 11:59:24PM +0200, Hartmut Pfarr wrote:
> {-# LANGUAGE OverloadedStrings #-}
> 
> import Database.PostgreSQL.Simple
> import Database.PostgreSQL.Simple.FromRow
> 
> hello :: (FromRow a) => IO [a]
> hello = do
>   conn <- connect defaultConnectInfo
>   query_ conn "select 2 + 2"

Either

    main = print =<< (hello :: IO [Int])

or give hello a monomorphic type signature, such as 

    hello :: IO [Int]

Tom