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use crate::common::*;
#[derive(Debug, Clone, Copy, PartialOrd, Ord, PartialEq, Eq, Hash, Default)]
pub struct ProductVal<A>(pub A);
impl<A> FromIterator<A> for ProductVal<A>
where
A: Product<A>,
{
fn from_iter<T: IntoIterator<Item = A>>(iter: T) -> Self {
let product: A = iter.into_iter().product();
Self(product)
}
}
impl<A> ProductVal<A> {
pub fn get(&self) -> &A {
&self.0
}
pub fn into_inner(self) -> A {
self.0
}
}
impl<A> Extend<A> for ProductVal<A>
where
A: Product<A>,
{
fn extend<T: IntoIterator<Item = A>>(&mut self, iter: T) {
let default: A = iter::empty().product();
let prod = iter::once(mem::replace(&mut self.0, default))
.chain(iter)
.product();
self.0 = prod;
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn product_test() {
let mut prod: ProductVal<usize> = iter::repeat(2).take(10).collect();
assert_eq!(*prod.get(), 1024);
prod.extend(1..=5);
assert_eq!(*prod.get(), 122880);
}
}