For the sake of good order, I am posting the different solutions as per Daniel Fischer's suggestions
in a tested module:
module TestIO
where
import Control.Monad
data Person = Person {name :: String, age :: Int} deriving Show
-- operator version of apply
infix 0 |>
(|>) :: a -> (a -> b) -> b
x |> f = f x
-- verbal version of (|>) operator
apply :: a -> (a -> b) -> b
apply x f = f x
setName :: String -> Person -> IO Person
setName s p = do
putStrLn "setting name"
return p {name=s}
setAge :: Int -> Person -> IO Person
setAge i p = do
putStrLn "setting age"
return p {age=i}
-- first way: using recursion
update :: [Person -> IO Person] -> Person -> IO Person
update [] p = return p
update (f:fs) p = do
p' <- f p
update fs p'
-- second way: using foldm and (|>) operator
update1 :: [Person -> IO Person] -> Person -> IO Person
update1 fs p = foldM (|>) p fs
-- third way: (|>) is now function apply
update2 :: [Person -> IO Person] -> Person -> IO Person
update2 fs p = foldM apply p fs
p1 = Person {name="alia", age=12}
p2 = update [(setName "sam"), (setAge 32)] p1
p3 = update1 [(setName "sue"), (setAge 40)] p1
p4 = update2 [(setName "jo"), (setAge 55)] p1
