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//! This file defines behaviours of catamorphisms and anamorphisms.
//!
//! A catamorphism collapses a recursive structure into a flat value,
//! whereas an anamorphism expands a value into a recursive structure.
use crate::{algebra::Algebra, coalgebra::Coalgebra, functor::Functor};
/// A type that implements Cata is capable of being collapsed into a single value.
///
/// The catamorphism consumes `self`.
pub trait Cata<T, F: Functor<T>, A: Algebra<T, F>> {
/// A catamorphism takes a recursive structure and an algebra for
/// the recursive structure, and returns a single, flat, collapsed
/// value.
fn cata(self, alg: A) -> T;
}
/// A type that implements Ana is capable of being expanded from a
/// flat value.
///
/// The anamorphism consumes `self`.
pub trait Ana<T, F: Functor<T>, C: Coalgebra<T, F>> {
/// An anamorphism takes a single, flat, collapsed value and a
/// co-algebra for a recursive structure, and returns that
/// recursive structure.
fn ana(value: T, coalg: C) -> Self;
}
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