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auto merge of #8428 : blake2-ppc/rust/peekable-iterators, r=thestinger
Peekable changes by @SimonSapin and original PR is #8396
2 parents de48274 + 0b35e3b commit ecfc9a8

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-107
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2 files changed

+138
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‎src/libextra/treemap.rs

Lines changed: 46 additions & 88 deletions
Original file line numberDiff line numberDiff line change
@@ -14,7 +14,8 @@
1414
1515

1616
use std::util::{swap, replace};
17-
use std::iterator::{FromIterator, Extendable};
17+
use std::iterator::{FromIterator, Extendable, Peekable};
18+
use std::cmp::Ordering;
1819

1920
// This is implemented as an AA tree, which is a simplified variation of
2021
// a red-black tree where red (horizontal) nodes can only be added
@@ -529,24 +530,24 @@ impl<T: TotalOrd> TreeSet<T> {
529530

530531
/// Visit the values (in-order) representing the difference
531532
pub fn difference<'a>(&'a self, other: &'a TreeSet<T>) -> Difference<'a, T> {
532-
Difference{a: Focus::new(self.iter()), b: Focus::new(other.iter())}
533+
Difference{a: self.iter().peekable(), b: other.iter().peekable()}
533534
}
534535

535536
/// Visit the values (in-order) representing the symmetric difference
536537
pub fn symmetric_difference<'a>(&'a self, other: &'a TreeSet<T>)
537538
-> SymDifference<'a, T> {
538-
SymDifference{a: Focus::new(self.iter()), b: Focus::new(other.iter())}
539+
SymDifference{a: self.iter().peekable(), b: other.iter().peekable()}
539540
}
540541

541542
/// Visit the values (in-order) representing the intersection
542543
pub fn intersection<'a>(&'a self, other: &'a TreeSet<T>)
543544
-> Intersection<'a, T> {
544-
Intersection{a: Focus::new(self.iter()), b: Focus::new(other.iter())}
545+
Intersection{a: self.iter().peekable(), b: other.iter().peekable()}
545546
}
546547

547548
/// Visit the values (in-order) representing the union
548549
pub fn union<'a>(&'a self, other: &'a TreeSet<T>) -> Union<'a, T> {
549-
Union{a: Focus::new(self.iter()), b: Focus::new(other.iter())}
550+
Union{a: self.iter().peekable(), b: other.iter().peekable()}
550551
}
551552
}
552553

@@ -560,61 +561,47 @@ pub struct TreeSetRevIterator<'self, T> {
560561
priv iter: TreeMapRevIterator<'self, T, ()>
561562
}
562563

563-
// Encapsulate an iterator and hold its latest value until stepped forward
564-
struct Focus<A, T> {
565-
priv iter: T,
566-
priv focus: Option<A>,
567-
}
568-
569-
impl<A, T: Iterator<A>> Focus<A, T> {
570-
fn new(mut it: T) -> Focus<A, T> {
571-
Focus{focus: it.next(), iter: it}
572-
}
573-
fn step(&mut self) {
574-
self.focus = self.iter.next()
575-
}
576-
}
577-
578564
/// Lazy iterator producing elements in the set difference (in-order)
579565
pub struct Difference<'self, T> {
580-
priv a: Focus<&'self T, TreeSetIterator<'self, T>>,
581-
priv b: Focus<&'self T, TreeSetIterator<'self, T>>,
566+
priv a: Peekable<&'self T, TreeSetIterator<'self, T>>,
567+
priv b: Peekable<&'self T, TreeSetIterator<'self, T>>,
582568
}
583569

584570
/// Lazy iterator producing elements in the set symmetric difference (in-order)
585571
pub struct SymDifference<'self, T> {
586-
priv a: Focus<&'self T, TreeSetIterator<'self, T>>,
587-
priv b: Focus<&'self T, TreeSetIterator<'self, T>>,
572+
priv a: Peekable<&'self T, TreeSetIterator<'self, T>>,
573+
priv b: Peekable<&'self T, TreeSetIterator<'self, T>>,
588574
}
589575

590576
/// Lazy iterator producing elements in the set intersection (in-order)
591577
pub struct Intersection<'self, T> {
592-
priv a: Focus<&'self T, TreeSetIterator<'self, T>>,
593-
priv b: Focus<&'self T, TreeSetIterator<'self, T>>,
578+
priv a: Peekable<&'self T, TreeSetIterator<'self, T>>,
579+
priv b: Peekable<&'self T, TreeSetIterator<'self, T>>,
594580
}
595581

596582
/// Lazy iterator producing elements in the set intersection (in-order)
597583
pub struct Union<'self, T> {
598-
priv a: Focus<&'self T, TreeSetIterator<'self, T>>,
599-
priv b: Focus<&'self T, TreeSetIterator<'self, T>>,
584+
priv a: Peekable<&'self T, TreeSetIterator<'self, T>>,
585+
priv b: Peekable<&'self T, TreeSetIterator<'self, T>>,
586+
}
587+
588+
/// Compare `x` and `y`, but return `short` if x is None and `long` if y is None
589+
fn cmp_opt<T: TotalOrd>(x: Option<&T>, y: Option<&T>,
590+
short: Ordering, long: Ordering) -> Ordering {
591+
match (x, y) {
592+
(None , _ ) => short,
593+
(_ , None ) => long,
594+
(Some(x1), Some(y1)) => x1.cmp(y1),
595+
}
600596
}
601597

602598
impl<'self, T: TotalOrd> Iterator<&'self T> for Difference<'self, T> {
603599
fn next(&mut self) -> Option<&'self T> {
604600
loop {
605-
match (self.a.focus, self.b.focus) {
606-
(None , _ ) => return None,
607-
(ret , None ) => { self.a.step(); return ret },
608-
(Some(a1), Some(b1)) => {
609-
let cmp = a1.cmp(b1);
610-
if cmp == Less {
611-
self.a.step();
612-
return Some(a1);
613-
} else {
614-
if cmp == Equal { self.a.step() }
615-
self.b.step();
616-
}
617-
}
601+
match cmp_opt(self.a.peek(), self.b.peek(), Less, Less) {
602+
Less => return self.a.next(),
603+
Equal => { self.a.next(); self.b.next(); }
604+
Greater => { self.b.next(); }
618605
}
619606
}
620607
}
@@ -623,23 +610,10 @@ impl<'self, T: TotalOrd> Iterator<&'self T> for Difference<'self, T> {
623610
impl<'self, T: TotalOrd> Iterator<&'self T> for SymDifference<'self, T> {
624611
fn next(&mut self) -> Option<&'self T> {
625612
loop {
626-
match (self.a.focus, self.b.focus) {
627-
(ret , None ) => { self.a.step(); return ret },
628-
(None , ret ) => { self.b.step(); return ret },
629-
(Some(a1), Some(b1)) => {
630-
let cmp = a1.cmp(b1);
631-
if cmp == Less {
632-
self.a.step();
633-
return Some(a1);
634-
} else {
635-
self.b.step();
636-
if cmp == Greater {
637-
return Some(b1);
638-
} else {
639-
self.a.step();
640-
}
641-
}
642-
}
613+
match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less) {
614+
Less => return self.a.next(),
615+
Equal => { self.a.next(); self.b.next(); }
616+
Greater => return self.b.next(),
643617
}
644618
}
645619
}
@@ -648,20 +622,16 @@ impl<'self, T: TotalOrd> Iterator<&'self T> for SymDifference<'self, T> {
648622
impl<'self, T: TotalOrd> Iterator<&'self T> for Intersection<'self, T> {
649623
fn next(&mut self) -> Option<&'self T> {
650624
loop {
651-
match (self.a.focus, self.b.focus) {
652-
(None , _ ) => return None,
653-
(_ , None ) => return None,
654-
(Some(a1), Some(b1)) => {
655-
let cmp = a1.cmp(b1);
656-
if cmp == Less {
657-
self.a.step();
658-
} else {
659-
self.b.step();
660-
if cmp == Equal {
661-
return Some(a1);
662-
}
663-
}
664-
},
625+
let o_cmp = match (self.a.peek(), self.b.peek()) {
626+
(None , _ ) => None,
627+
(_ , None ) => None,
628+
(Some(a1), Some(b1)) => Some(a1.cmp(b1)),
629+
};
630+
match o_cmp {
631+
None => return None,
632+
Some(Less) => { self.a.next(); }
633+
Some(Equal) => { self.b.next(); return self.a.next() }
634+
Some(Greater) => { self.b.next(); }
665635
}
666636
}
667637
}
@@ -670,22 +640,10 @@ impl<'self, T: TotalOrd> Iterator<&'self T> for Intersection<'self, T> {
670640
impl<'self, T: TotalOrd> Iterator<&'self T> for Union<'self, T> {
671641
fn next(&mut self) -> Option<&'self T> {
672642
loop {
673-
match (self.a.focus, self.b.focus) {
674-
(ret , None) => { self.a.step(); return ret },
675-
(None , ret ) => { self.b.step(); return ret },
676-
(Some(a1), Some(b1)) => {
677-
let cmp = a1.cmp(b1);
678-
if cmp == Greater {
679-
self.b.step();
680-
return Some(b1);
681-
} else {
682-
self.a.step();
683-
if cmp == Equal {
684-
self.b.step();
685-
}
686-
return Some(a1);
687-
}
688-
}
643+
match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less) {
644+
Less => return self.a.next(),
645+
Equal => { self.b.next(); return self.a.next() }
646+
Greater => return self.b.next(),
689647
}
690648
}
691649
}

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