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use std::fmt::Debug;
fn foldl<T, U, F>(values: &[T], initial: U, mut function: F) -> U
where
U: Clone + Debug,
T: Debug,
F: FnMut(U, &T) -> U,
{
match values {
[head, tail @ ..] => foldl(tail, function(initial, head), function),
[] => {
let res = initial.clone();
res
}
}
}
fn foldr<T, U, F>(values: &[T], initial: U, mut function: F) -> U
where
U: Clone,
F: FnMut(&T, U) -> U,
{
match values {
[head @ .., tail] => foldr(head, function(tail, initial), function),
[] => {
let res = initial.clone();
res
}
}
}
pub fn main() {
let x = &[1, 2, 3, 4, 5];
let product = foldl(x, 1, |a, b| a * *b);
assert_eq!(product, 120);
let sum = foldr(x, 0, |a, b| *a + b);
assert_eq!(sum, 15);
}
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