Unless I’m totally misreading something, the logging example _doesn’t_ capture the logger. Everything that accesses it also takes it as a parameter. So it’s really equivalent to
loggerExample :: IO ()
loggerExample = do
let logger = newLogger 0
logMsg logger 1 "Getting user"
user <- getUser
logMsg logger 1 ("Is VIP: " <> show (isVip user))
let modification = if isVip user then (+ 10) else id
d <- do
-- Instead of overriding it with a continuation, we can just shadow the variable
-- (the (<-) and pure are necessary since regular lets are recursive and don't allow shadowing)
logger <- pure (modifySeverity logger modification)
logMsg logger 0 "Getting data"
getData user
writeData d
logMsg logger 0 "Done"
and then I don’t see the advantage of passing this additional reference around if all you’re doing with it is modifying it in a lexically scoped way like you already can with regular variables