fx-rs 0.1.1-dev0

Algebraic Effects inspired by Kyo and Fx.go
Documentation 
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use std::marker::PhantomData;

use crate::Fx;

pub struct State<'f, S: Clone>(PhantomData<&'f S>);
impl<'f, S: Clone> State<'f, S> {
    pub fn get() -> Fx<'f, S, S> {
        Fx::pending(Fx::value)
    }

    pub fn set(s: S) -> Fx<'f, S, S> {
        Fx::immediate(s.clone(), s)
    }

    pub fn map<F>(f: F) -> Fx<'f, S, S>
    where
        F: FnOnce(S) -> S + Clone + 'f,
    {
        Self::map_m(|s| Fx::value(f(s)))
    }

    pub fn map_m<F>(f: F) -> Fx<'f, S, S>
    where
        F: FnOnce(S) -> Fx<'f, S, S> + Clone + 'f,
    {
        Self::get().map_m(f).map_m(State::set)
    }

    pub fn update<T, F>(f: F) -> Fx<'f, (S, T), S>
    where
        T: Clone,
        F: FnOnce(S) -> Fx<'f, T, S> + Clone + 'f,
    {
        Self::get()
            .flat_map(|s| f(s).flat_map(|s| Self::set(s)))
            .contra_map(
                |(s, t): (S, T)| (s.clone(), (t, s)),
                |_, (_, (t, s))| (s, t),
            )
    }
}