Works in ghci but not in the file
printf.hs:37:19:
Ambiguous type variable `a0' in the constraints:
  (Format a0) arising from a use of `showManyP' at printf.hs:37:19-27
  (Num a0) arising from the literal `10' at printf.hs:37:34-35
Probable fix: add a type signature that fixes these type variable(s)
In the second argument of `($)', namely `showManyP "%d" 10'
In the expression: putStrLn $ showManyP "%d" 10
In an equation for `main': main = putStrLn $ showManyP "%d" 10
Failed, modules loaded: none.

{-# LANGUAGE OverlappingInstances #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE TypeSynonymInstances #-}
import Data.List (intercalate,isPrefixOf)
class Showable a where
    showManyP :: String -> a

instance Showable String where
    showManyP str = str

instance (Showable s,Format a) => Showable (a->s) where
    showManyP str a = showManyP (format str a)

class Format a where
    format :: String -> a -> String

instance Format String where
    format str a = replace "%s" str a

instance Format Char where
    format str a = replace "%c" str [a]

instance Num a=>Format a where
    format str a = replace "%d" str (show a)

replace :: String -> String -> String -> String
replace f str value = intercalate value $ split str f

split :: String -> String -> [String]
split [] f = [[]]
split str [] = [str]
split str@(x:xs) f | isPrefixOf f str = [[],drop (length f) str]
                   | otherwise = let (y:ys) = split xs f
                                 in [x:y] ++ ys