1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
pub trait ModLens<'a, S, A> {
fn view(&self, s: &'a mut S) -> &'a mut A;
}
pub struct ModLensImpl<'a, 's, S, A>(&'s Fn(&'a mut S) -> &'a mut A);
pub struct ModLensCompoundImpl<'a, 's, S, A, B> {
lhs: &'s ModLens<'a, S, A>,
rhs: &'s ModLens<'a, A, B>,
}
impl <'a, 's, S, A> ModLens<'a, S, A> for ModLensImpl<'a, 's, S, A> {
fn view(&self, s: &'a mut S) -> &'a mut A {
(self.0)(s)
}
}
impl <'a, 's, S, A:'a, B> ModLens<'a, S, B> for ModLensCompoundImpl<'a, 's, S, A, B> {
fn view(&self, s: &'a mut S) -> &'a mut B {
self.rhs.view(self.lhs.view(s))
}
}
pub fn mod_compose<'a, 's, S, A, B>(lhs: &'s ModLens<'a, S, A>, rhs: &'s ModLens<'a, A, B>) -> ModLensCompoundImpl<'a, 's, S, A, B> {
ModLensCompoundImpl {
lhs: lhs,
rhs: rhs,
}
}
pub fn mod_lens<'a, 's, S, A>(getter: &'s Fn(&'a mut S) -> &'a mut A) -> ModLensImpl<'a, 's, S, A> {
ModLensImpl(getter)
}