/// two `Step` objects.
#[unstable(feature = "step_trait",
reason = "likely to be replaced by finer-grained traits",
- issue = "27741")]
+ issue = "42168")]
pub trait Step: PartialOrd + Sized {
/// Steps `self` if possible.
fn step(&self, by: &Self) -> Option<Self>;
($($t:ty)*) => ($(
#[unstable(feature = "step_trait",
reason = "likely to be replaced by finer-grained traits",
- issue = "27741")]
+ issue = "42168")]
impl Step for $t {
#[inline]
fn step(&self, by: &$t) -> Option<$t> {
($($t:ty)*) => ($(
#[unstable(feature = "step_trait",
reason = "likely to be replaced by finer-grained traits",
- issue = "27741")]
+ issue = "42168")]
impl Step for $t {
#[inline]
fn step(&self, by: &$t) -> Option<$t> {
($($t:ty)*) => ($(
#[unstable(feature = "step_trait",
reason = "likely to be replaced by finer-grained traits",
- issue = "27741")]
+ issue = "42168")]
impl Step for $t {
#[inline]
fn step(&self, by: &$t) -> Option<$t> {
#[inline]
fn next(&mut self) -> Option<A> {
- use ops::RangeInclusive::*;
-
- // this function has a sort of odd structure due to borrowck issues
- // we may need to replace self.range, so borrows of start and end need to end early
-
- let (finishing, n) = match self.range {
- Empty { .. } => return None, // empty iterators yield no values
-
- NonEmpty { ref mut start, ref mut end } => {
- let rev = self.step_by.is_negative();
-
- // march start towards (maybe past!) end and yield the old value
- if (rev && start >= end) ||
- (!rev && start <= end)
- {
- match start.step(&self.step_by) {
- Some(mut n) => {
- mem::swap(start, &mut n);
- (None, Some(n)) // yield old value, remain non-empty
- },
- None => {
- let mut n = end.clone();
- mem::swap(start, &mut n);
- (None, Some(n)) // yield old value, remain non-empty
- }
- }
- } else {
- // found range in inconsistent state (start at or past end), so become empty
- (Some(end.replace_zero()), None)
- }
- }
- };
+ let rev = self.step_by.is_negative();
- // turn into an empty iterator if we've reached the end
- if let Some(end) = finishing {
- self.range = Empty { at: end };
+ if (rev && self.range.start >= self.range.end) ||
+ (!rev && self.range.start <= self.range.end)
+ {
+ match self.range.start.step(&self.step_by) {
+ Some(n) => {
+ Some(mem::replace(&mut self.range.start, n))
+ },
+ None => {
+ let last = self.range.start.replace_one();
+ self.range.end.replace_zero();
+ self.step_by.replace_one();
+ Some(last)
+ },
+ }
+ }
+ else {
+ None
}
-
- n
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
- use ops::RangeInclusive::*;
-
- match self.range {
- Empty { .. } => (0, Some(0)),
-
- NonEmpty { ref start, ref end } =>
- match Step::steps_between(start,
- end,
- &self.step_by) {
- Some(hint) => (hint.saturating_add(1), hint.checked_add(1)),
- None => (0, None)
- }
+ match Step::steps_between(&self.range.start,
+ &self.range.end,
+ &self.step_by) {
+ Some(hint) => (hint.saturating_add(1), hint.checked_add(1)),
+ None => (0, None)
}
}
}
#[inline]
fn next(&mut self) -> Option<A> {
- use ops::RangeInclusive::*;
-
- // this function has a sort of odd structure due to borrowck issues
- // we may need to replace self, so borrows of self.start and self.end need to end early
-
- let (finishing, n) = match *self {
- Empty { .. } => (None, None), // empty iterators yield no values
-
- NonEmpty { ref mut start, ref mut end } => {
- if start == end {
- (Some(end.replace_one()), Some(start.replace_one()))
- } else if start < end {
- let mut n = start.add_one();
- mem::swap(&mut n, start);
-
- // if the iterator is done iterating, it will change from
- // NonEmpty to Empty to avoid unnecessary drops or clones,
- // we'll reuse either start or end (they are equal now, so
- // it doesn't matter which) to pull out end, we need to swap
- // something back in
-
- (if n == *end { Some(end.replace_one()) } else { None },
- // ^ are we done yet?
- Some(n)) // < the value to output
- } else {
- (Some(start.replace_one()), None)
- }
- }
- };
-
- // turn into an empty iterator if this is the last value
- if let Some(end) = finishing {
- *self = Empty { at: end };
+ use cmp::Ordering::*;
+
+ match self.start.partial_cmp(&self.end) {
+ Some(Less) => {
+ let n = self.start.add_one();
+ Some(mem::replace(&mut self.start, n))
+ },
+ Some(Equal) => {
+ let last = self.start.replace_one();
+ self.end.replace_zero();
+ Some(last)
+ },
+ _ => None,
}
-
- n
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
- use ops::RangeInclusive::*;
-
- match *self {
- Empty { .. } => (0, Some(0)),
+ if !(self.start <= self.end) {
+ return (0, Some(0));
+ }
- NonEmpty { ref start, ref end } =>
- match Step::steps_between_by_one(start, end) {
- Some(hint) => (hint.saturating_add(1), hint.checked_add(1)),
- None => (0, None),
- }
+ match Step::steps_between_by_one(&self.start, &self.end) {
+ Some(hint) => (hint.saturating_add(1), hint.checked_add(1)),
+ None => (0, None),
}
}
}
{
#[inline]
fn next_back(&mut self) -> Option<A> {
- use ops::RangeInclusive::*;
-
- // see Iterator::next for comments
-
- let (finishing, n) = match *self {
- Empty { .. } => return None,
-
- NonEmpty { ref mut start, ref mut end } => {
- if start == end {
- (Some(start.replace_one()), Some(end.replace_one()))
- } else if start < end {
- let mut n = end.sub_one();
- mem::swap(&mut n, end);
-
- (if n == *start { Some(start.replace_one()) } else { None },
- Some(n))
- } else {
- (Some(end.replace_one()), None)
- }
- }
- };
-
- if let Some(start) = finishing {
- *self = Empty { at: start };
+ use cmp::Ordering::*;
+
+ match self.start.partial_cmp(&self.end) {
+ Some(Less) => {
+ let n = self.end.sub_one();
+ Some(mem::replace(&mut self.end, n))
+ },
+ Some(Equal) => {
+ let last = self.end.replace_zero();
+ self.start.replace_one();
+ Some(last)
+ },
+ _ => None,
}
-
- n
}
}
projects / rust.git / commitdiff