Struct morphism::Morphism

pub struct Morphism<'a, A, B = A> { /* fields omitted */ }

A suspended chain of closures that behave as a function from type A to type B.

When B = A the parameter B can be omitted: Morphism<'a, A> is equivalent to Morphism<'a, A, A>. This is convenient for providing annotations with Morphism::new().

Methods

impl Morphism<'static, Void>

fn new<'a, A>() -> Morphism<'a, A>

Create the identity chain.

Example

use morphism::Morphism;

assert_eq!(Morphism::new::<u64>().run(42u64), 42u64);

impl<'a, B, C> Morphism<'a, B, C>

unsafe fn unsafe_push_front<A, F>(&mut self, f: F) where
    F: Fn(A) -> B + 'a, 

fn head<A, F>(self, f: F) -> Morphism<'a, A, C> where
    F: Fn(A) -> B + 'a, 

Attach a closure to the front of the closure chain. This corresponds to closure composition at the domain (pre-composition).

Example

use morphism::Morphism;

let f = Morphism::new::<Option<String>>()
    .head(|x: Option<u64>| x.map(|y| y.to_string()))
    .head(|x: Option<u64>| x.map(|y| y - 42u64))
    .head(|x: u64| Some(x + 42u64 + 42u64));
assert_eq!(f.run(0u64), Some("42".to_string()));

fn push_front<F>(&mut self, f: F) where
    F: Fn(B) -> B + 'a, 

Mutate a given Morphism<B, C> by pushing a closure of type Fn(B) -> B onto the front of the chain.

Example

use morphism::Morphism;

let mut f = Morphism::new::<u64>();
for i in (0..10u64) {
    (&mut f).push_front(move |x| x + i);
}
assert_eq!(f.run(0u64), 45u64);

impl<'a, A, B> Morphism<'a, A, B>

unsafe fn unsafe_push_back<C, F>(&mut self, f: F) where
    F: Fn(B) -> C + 'a, 

fn tail<C, F>(self, f: F) -> Morphism<'a, A, C> where
    F: Fn(B) -> C + 'a, 

Attach a closure to the back of the closure chain. This corresponds to closure composition at the codomain (post-composition).

Example

use morphism::Morphism;

let f = Morphism::new::<u64>()
    .tail(|x| Some(x + 42u64 + 42u64))
    .tail(|x| x.map(|y| y - 42u64))
    .tail(|x| x.map(|y| y.to_string()));
assert_eq!(f.run(0u64), Some("42".to_string()));

fn push_back<F>(&mut self, f: F) where
    F: Fn(B) -> B + 'a, 

Mutate a given Morphism<A, B> by pushing a closure of type Fn(B) -> B onto the back of the chain.

Example

use morphism::Morphism;

let mut f = Morphism::new::<u64>();
for i in (0..10u64) {
    (&mut f).push_back(move |x| x + i);
}
assert_eq!(f.run(0u64), 45u64);

fn then<C>(self, other: Morphism<'a, B, C>) -> Morphism<'a, A, C>

Compose one Morphism with another.

Example

use morphism::Morphism;

let mut f = Morphism::new::<u64>();
for _ in (0..100000u64) {
    f = f.tail(|x| x + 42u64);
}
// the type changes to Morphism<u64, Option<u64>> so rebind f
let f = f.tail(|x| Some(x));

let mut g = Morphism::new::<Option<u64>>();
for _ in (0..99999u64) {
    g = g.tail(|x| x.map(|y| y - 42u64));
}
// the type changes to Morphism<Option<u64>, String> so rebind g
let g = g.tail(|x| x.map(|y| y + 1000u64).unwrap().to_string());

assert_eq!(f.then(g).run(0u64), "1042".to_string());

fn run(&self, x: A) -> B

Given an argument, run the chain of closures in a loop and return the final result.