Trait Monoid 

pub trait Monoid<'a>: Semigroup<'a> {
    // Required method
    fn empty() -> Self;
}

A type class for monoids.

Monoid extends Semigroup with an identity element. A monoid is a set equipped with an associative binary operation and an identity element.

In functional programming, monoids are useful for combining values in a consistent way, especially when accumulating results or folding collections.

Laws

Monoid instances must satisfy the following laws:

• Left identity: append(empty(), x) = x.
• Right identity: append(x, empty()) = x.
• Associativity: append(append(x, y), z) = append(x, append(y, z)).

Required Methods

fn empty() -> Self

Returns the identity element for the monoid.

Type Signature

Monoid a => () -> a

Returns

The identity element which, when combined with any other element using the semigroup operation, leaves the other element unchanged.

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> Monoid<'a> for String

fn empty() -> Self

Examples

use fp_library::functions::empty;

assert_eq!(
    empty::<String>(),
    ""
);

impl<'a, A> Monoid<'a> for Vec<A>

where A: Clone,

fn empty() -> Self

Examples

use fp_library::functions::empty;

assert_eq!(
    empty::<Vec<()>>(),
    []
);

impl<'b, A: 'b + Clone, B: Monoid<'b> + 'b> Monoid<'b> for Rc<dyn Fn(A) -> B + 'b>

fn empty() -> Self

impl<'b, A: 'b + Clone, B: Monoid<'b> + 'b> Monoid<'b> for Arc<dyn Fn(A) -> B + 'b>

fn empty() -> Self

Implementors

impl<'a, CategoryBrand: 'a + Category, A> Monoid<'a> for Endomorphism<'a, CategoryBrand, A>

where Apply1L2T<'a, CategoryBrand, A, A>: Clone,

impl<'a, ClonableFnBrand: 'a + ClonableFn, A> Monoid<'a> for Endofunction<'a, ClonableFnBrand, A>