Trait Functor

pub trait Functor<'a, A> {
    type Target<T>;

    // Required method
    fn fmap<B, F>(self, f: F) -> Self::Target<B>
       where F: Fn(A) -> B + 'a;
}

A Functor lets you change the type parameter of a generic type.

A Functor defines a method fmap on a type F<_>: Functor which converts an F<A> to F<B> using a function Fn(A) -> B applied to the As inside it.

You can also use this just to modify the values inside your container value without changing their type, if the mapping function returns a value of the same type. This is called an “endofunctor.”

Required Associated Types

type Target<T>

Required Methods

fn fmap<B, F>(self, f: F) -> Self::Target<B>

where F: Fn(A) -> B + 'a,

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl<A> Functor<'_, A> for Option<A>

type Target<T> = Option<T>

fn fmap<B, F>(self, f: F) -> Self::Target<B>

where F: Fn(A) -> B,

impl<A> Functor<'_, A> for LinkedList<A>

type Target<T> = LinkedList<T>

fn fmap<B, F>(self, f: F) -> Self::Target<B>

where F: Fn(A) -> B,

impl<A> Functor<'_, A> for VecDeque<A>

type Target<T> = VecDeque<T>

fn fmap<B, F>(self, f: F) -> Self::Target<B>

where F: Fn(A) -> B,

impl<A> Functor<'_, A> for Vec<A>

type Target<T> = Vec<T>

fn fmap<B, F>(self, f: F) -> Self::Target<B>

where F: Fn(A) -> B,

impl<A, E> Functor<'_, A> for Result<A, E>

type Target<T> = Result<T, E>

fn fmap<B, F>(self, f: F) -> Self::Target<B>

where F: Fn(A) -> B,

Implementors

impl<'a, A> Functor<'a, A> for Effect<'a, A>

where A: 'a,

type Target<T> = Effect<'a, T>

impl<'a, A: 'a, E: 'a> Functor<'a, A> for IO<'a, A, E>

type Target<T> = IO<'a, T, E>