//@NO-IMPLICIT-PRELUDE
//! Implementation of the `Functor` type

/// A `Functor` represents an action on a parameterized type which does not
/// change the structure with the mapped type.
///
/// The following laws should hold:
///
/// * `map id == id`
/// * `map (f << g) == map f << map g`
#[implicit]
type Functor f = {
    /// Apply the supplied function to the contents of `f a`, converting it to
    /// an `f b`
    ///
    /// # Examples
    ///
    /// * `option.functor.map show_Int.show (Some 1) == Some "1"`
    /// * `result.functor.map show_Int.show (Some 1) == Ok "1"`
    /// * `list.functor.map show_Int.show (list.of [1, 2]) == list.of ["1", "2"]`
    ///
    /// # Note
    ///
    /// * Known as `fmap` in Haskell
    map : forall a b . (a -> b) -> f a -> f b
}

let map ?functor : [Functor f] -> (a -> b) -> f a -> f b = functor.map

{ Functor, map }