Il 31 dicembre 2020 alle 23:04 Lawrence Bottorff ha scritto:
:t (123,"Hi",234.0) (123,"Hi",234.0) :: (Fractional c, Num a) => (a, [Char], c)
When you do not write a signature yourself GHC/GHCi tries to infer it. Alas — for certain types — GHC tries to default it -- prova.hs a = (123, "Hi", 234.0) λ> :load prova.hs [1 of 1] Compiling Main ( prova.hs, interpreted ) Ok, one module loaded. λ> :t a a :: (Integer, [Char], Double) while GHCi goes for a more general type λ> b = (123, "Hi", 234.0) λ> :t b (123,"Hi",234.0) :: (Fractional c, Num a) => (a, [Char], c) A couple of considerations: - those are typeclasses — tl;dr they are interfaces providing a specific type of polymorphism. Ignore them for now if your text hasn’t explained them yet. - When GHCi gives a type signature with typeclasses but you would rather see concrete types, use `+d` λ> :t +d b b :: (Integer, [Char], Double)