Trait currycompose::Compose
source · pub trait Compose<F, XG, XF>: Sized {
// Required method
fn compose(self, with: F) -> Composition<Self, F, XG, XF>;
}
Expand description
https://en.wikipedia.org/wiki/Function_composition
Trait for composing two functions (currying and non-curring composition)
Non-currying composition: h(x) = g ∘ f = g(f(x))
Currying composition: h(…, x) = g ∘ f = g(f(x), …)
When currying, arguments of the function being curried with (f) is moved to the end of the argument-list
Both operands must implement FnOnce. If both implement FnMut or Fn, the resulting composition will also implement these traits.
g must also have one or more argument, where the first argument type equals the return type of f.
#![feature(generic_const_exprs)]
use currycompose::*;
// g ∘ f
// where
// g :: f32 -> f32
// f :: u8 -> f32
// g ∘ f :: u8 -> f32
let g = |x: f32| x*x;
let f = |x: u8| x as f32;
let gf = g.compose(f);
let x = 1;
assert_eq!(gf(x), g(f(x)));
// g ∘ f
// where
// g :: f32 -> f32 -> f32
// f :: u8 -> f32
// g ∘ f :: f32 -> u8 -> f32
let g = |x: f32, y: f32| x + y;
let f = gf;
let gf = g.compose(f);
let x = 1;
let y = 1.0;
// note here the argument x has been shifted to the end of the args in gf
assert_eq!(gf(y, x), g(f(x), y));
// g ∘ f ∘ f
// where
// g :: f32 -> f32 -> f32
// f :: u8 -> f32
// g ∘ f ∘ f :: u8 -> u8 -> f32
let gff = gf.compose(f);
let x = 1;
let y = 1;
assert_eq!(gff(x, y), g(f(x), f(y)));
Required Methods§
sourcefn compose(self, with: F) -> Composition<Self, F, XG, XF>
fn compose(self, with: F) -> Composition<Self, F, XG, XF>
Composing two functions
h(x) = g ∘ f = g(f(x))