-- Most of the things defined here are already defined
-- in the Prelude.
id : 'A -> 'A
id x = x -- Identity function
show : String -> String
show = id -- naturally.
-- Showable represents the
-- union of all types that implement
-- the show function on type 'A.
ability Showable on 'A {
show : 'A -> String
}
-- Example
num_to_string : Showable & Number -> String
num_to_string n = show n
-- Converts only Numbers that are showable.
-- This gives us some early checking essentially.
stdout = IO::STDOUT ()
-- Same as `puts'/`put'
println : Showable -> [] -- saying [] will throw away the result and give ().
println s = [| s; "\n" |] |> map stdout.IO::write <> show
println s = map (s |-> stdout.IO::write (show s)) [| s; "\n" |]
println s = IO::write stdout <| show s + "\n" -- all equiv.
-- So if we try to print something that's
-- not showable, it won't accept it.
-- The error should tell you to consider implementing
-- `show' on that type.
