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use crate::{
functor::Functor,
recursive::{Collapse, Expand},
recursive_tree::{RecursiveTree, RecursiveTreeRef},
};
#[derive(Debug, Clone, Copy)]
pub struct StackMarker;
impl<A, U, O: Functor<StackMarker, Unwrapped = A, To = U>> Expand<A, O>
for RecursiveTree<U, StackMarker>
{
fn expand_layers<F: Fn(A) -> O>(a: A, generate_layer: F) -> Self {
let mut frontier = Vec::from([a]);
let mut elems = vec![];
while let Some(seed) = frontier.pop() {
let layer = generate_layer(seed);
let mut topush = Vec::new();
let layer = layer.fmap(|aa| {
topush.push(aa);
StackMarker
});
frontier.extend(topush.into_iter().rev());
elems.push(layer);
}
elems.reverse();
Self {
elems,
_underlying: std::marker::PhantomData,
}
}
}
impl<A, O, U: Functor<A, To = O, Unwrapped = StackMarker>> Collapse<A, O>
for RecursiveTree<U, StackMarker>
{
fn collapse_layers<F: FnMut(O) -> A>(self, mut fold_layer: F) -> A {
let mut result_stack = Vec::new();
for layer in self.elems.into_iter() {
let layer = layer.fmap(|_| result_stack.pop().unwrap());
result_stack.push(fold_layer(layer));
}
result_stack.pop().unwrap()
}
}
impl<'a, A, O: 'a, U> Collapse<A, O> for RecursiveTreeRef<'a, U, StackMarker>
where
&'a U: Functor<A, To = O, Unwrapped = StackMarker>,
{
fn collapse_layers<F: FnMut(O) -> A>(self, mut fold_layer: F) -> A {
let mut result_stack = Vec::with_capacity(32);
for layer in self.elems.iter() {
let layer = layer.fmap(|_| result_stack.pop().unwrap());
result_stack.push(fold_layer(layer));
}
result_stack.pop().unwrap()
}
}