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pub struct Iterware<I, F> {
iter: I,
f: F,
}
impl<I: Iterator, F> Iterator for Iterware<I, F>
where
F: Fn(&I::Item) -> (),
{
type Item = I::Item;
fn next(&mut self) -> Option<Self::Item> {
match self.iter.next() {
Some(t) => {
(self.f)(&t);
Some(t)
}
None => None,
}
}
}
pub trait IteratorMiddleware<I, F> {
fn middleware(self, f: F) -> Iterware<I, F>;
}
impl<I, F> IteratorMiddleware<I, F> for I
where
I: Iterator,
F: Fn(&I::Item) -> (),
{
fn middleware(self, f: F) -> Iterware<I, F> {
Iterware { iter: self, f }
}
}
#[cfg(test)]
mod tests {
use crate::IteratorMiddleware;
#[test]
fn test_borrow() {
let values = vec![1, 2, 3, 4, 5];
let sum: i32 = values
.into_iter()
.middleware(|value| println!("Adding value {}", value))
.sum();
println!("The sum is {}", sum);
assert_eq!(sum, 15);
}
}