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docs(drawing::loose): document how 'prev_loose' works

This commit is contained in:
Ellen Emilia Anna Zscheile 2025-01-30 22:25:51 +01:00 committed by mikolaj
parent 5dab7d9100
commit 67c4933b09
1 changed files with 10 additions and 5 deletions
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15
src/drawing/loose.rs
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@ -24,11 +24,16 @@ pub trait GetPrevNextLoose {
fn next_loose(&self, maybe_prev: Option<LooseIndex>) -> Option<LooseIndex>;
fn prev_loose(&self, maybe_next: Option<LooseIndex>) -> Option<LooseIndex> {
if maybe_next.is_some() {
self.next_loose(maybe_next)
} else {
self.next_loose(self.next_loose(None))
}
// `next_loose` and `prev_loose` do exactly the same thing
// when `maybe_*` is `Some(_)`,
// but otherwise, they start in opposite direction, here by going via:
let maybe_prev = maybe_next.or_else(|| {
let default_neighbor = self.next_loose(None);
// * normally, one would retrieve the next element via `default_neighbor.next_loose(self)`
// * `self.next_loose(default_neighbor)` on the other hand inverts the direction we're iterating towards.
default_neighbor
});
self.next_loose(maybe_prev)
}
}