Function not evaluating in GHCI

Question

If I assign a var to maxBound :

let bInt = maxBound

evaluation of bInt prints ()

but if I type bInt

bInt :: Int
prints : 9223372036854775807

Why does bInt not evaluate until I type

bInt (bInt :: Int) ?

Answer 1

maxBound is a function in the Bounded type class. By default, GHCi appears to choose the instance for (), which returns (). You can force it to use another instance by adding a type signature.

let bInt :: Int; bInt = maxBound
bInt -- 9223372036854775807

let x = maxBound
x :: () -- ()
x :: Bool -- True
x :: Char -- '\1114111'