use super::functor::Functor;
use super::HKT;
use super::containers::*;
pub trait Applicative<U>: Functor<U> {
fn pure_(value: U) -> Self::T
where
Self: HKT<U, C = U>;
fn seq<F>(&self, fs: <Self as HKT<F>>::T) -> <Self as HKT<U>>::T
where
F: Fn(&<Self as HKT<U>>::C) -> U,
Self: HKT<F>;
}
macro_rules! applicative {
($($t:ident),* $(,)?) => {
$(
applicative!(@impl $t);
)*
};
(@impl $t:ident) => {
impl<T, U> Applicative<U> for $t<T> {
fn pure_(value: U) -> Self::T {
$t::new(value)
}
fn seq<F>(&self, fs: <Self as HKT<F>>::T) -> $t<U>
where
F: Fn(&<Self as HKT<U>>::C) -> U,
{
let v = fs(self);
$t::new(v)
}
}
};
}
#[cfg(any(feature = "std", all(feature = "alloc", no_std)))]
applicative!(Arc, Box, Rc);
impl<T, U> Applicative<U> for Option<T> {
fn pure_(value: U) -> Self::T {
Some(value)
}
fn seq<F>(&self, fs: <Self as HKT<F>>::T) -> Option<U>
where
F: Fn(&T) -> U,
{
match *self {
Some(ref value) => match fs {
Some(f) => Some(f(value)),
None => None,
},
None => None,
}
}
}
impl<T, U> Applicative<U> for Vec<T> {
fn pure_(value: U) -> Self::T {
vec![value]
}
fn seq<F>(&self, fs: <Self as HKT<F>>::T) -> Vec<U>
where
F: Fn(&T) -> U,
{
let mut result = Vec::new();
for (i, f) in fs.into_iter().enumerate() {
let v = (f)(&self[i]);
result.push(v)
}
return result;
}
}