Crate fmap

Functors in Rust

The following traits are provided by this module:

• Functor provides a general fmap method, which is a generalization of Option::map, Result::map, and so on, and which is implemented for a variety of types in the standard library.
• FunctorSelf is a special case of Functor where types aren’t changed when mapping. It is automatically implemented where applicable but must be added as a bound in certain cases.
• FunctorMut is a special case of FunctorSelf whose fmap_mut method operates on &mut self. It is not implemented automatically, but this crate provides implementations for all types in the standard library for which Functor is implemented.
• Contravariant, ContravariantSelf, and ContravariantMut which are the contravariant equivalents of the previous three traits.

Traits

• Contravariant
  Contravariant functor (e.g. Sender<B> which can be converted into Sender<A> by providing an Fn(A) -> B to rmap)
• ContravariantMut
  Same as ContravariantSelf but works on &mut self
• ContravariantSelf
  A Contravariant functor where type Self::Consumee isn’t changed
• Functor
  Generic type (e.g. T<A>) whose inner type can be mapped over (e.g. resulting in T<B>)
• FunctorMut
  Same as FunctorSelf but works on &mut self
• FunctorSelf
  A Functor which can be mapped from one type to the same type