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use ::{Selector1, Selector2};
pub fn new<A1, A2, I1, I2, F, R>(input1: I1, input2: I2, selector: F) -> impl Selector2<A1, A2, Output = R>
where F: FnMut(&I1::Output, &I2::Output) -> R,
I1: Selector1<A1>,
I1::Output: Clone + Eq,
I2: Selector1<A2>,
I2::Output: Clone + Eq,
R: Clone {
Select2 {
selector,
value: None,
input1,
output1: None,
input2,
output2: None,
}
}
struct Select2<A1, A2, I1: Selector1<A1>, I2: Selector1<A2>, F, R> {
selector: F,
value: Option<R>,
input1: I1,
output1: Option<I1::Output>,
input2: I2,
output2: Option<I2::Output>,
}
impl<A1, A2, F, I1, I2, R> Selector2<A1, A2> for Select2<A1, A2, I1, I2, F, R>
where F: FnMut(&I1::Output, &I2::Output) -> R,
I1: Selector1<A1>,
I1::Output: Clone + Eq,
I2: Selector1<A2>,
I2::Output: Clone + Eq,
R: Clone {
type Output = R;
fn select(&mut self, arg1: A1, arg2: A2) -> Self::Output {
let input1 = Some(self.input1.select(arg1));
let input2 = Some(self.input2.select(arg2));
if input1 != self.output1 || input2 != self.output2 {
self.value = Some((self.selector)(
input1.as_ref().unwrap(),
input2.as_ref().unwrap(),
));
self.output1 = input1;
self.output2 = input2;
}
self.value.as_ref().map(Clone::clone).unwrap()
}
}
#[cfg(test)]
mod tests {
use super::*;
use select1::{new as new1};
#[test]
fn smoke() {
let mut selector = new(
|num: u32| num + 1,
|num: u32| num + 2,
|num1, num2| (*num1, *num2),
);
assert_eq!(selector.select(1, 2), (2, 4));
assert_eq!(selector.select(1, 2), (2, 4));
}
#[test]
fn compose() {
let base1 = new1(|num: u32| num, |num| num * 2);
let base2 = new1(|num: u32| num, |num| num * 3);
let mut sel = new(base1, base2, |num1, num2| num1 + num2);
assert_eq!(sel.select(1, 1), 5);
}
#[test]
fn memo() {
let mut computations = 0;
{
let mut selector = new(
|num: u32| num + 1,
|num: u32| num + 2,
|num1, num2| {
computations += 1;
(*num1, *num2)
},
);
assert_eq!(selector.select(1, 2), (2, 4));
assert_eq!(selector.select(1, 2), (2, 4));
}
assert_eq!(computations, 1);
{
let mut selector = new(
|num: u32| num + 1,
|num: u32| num + 2,
|num1, num2| {
computations += 1;
(*num1, *num2)
},
);
assert_eq!(selector.select(1, 3), (2, 5));
assert_eq!(selector.select(1, 3), (2, 5));
}
assert_eq!(computations, 2);
}
}