From d48e496c5f8ac592ea50f53fac92ae2315080119 Mon Sep 17 00:00:00 2001
From: David Sehnal <david.sehnal@gmail.com>
Date: Fri, 20 Oct 2017 13:53:05 +0200
Subject: [PATCH] simplified iterators
---
src/structure/collections/int-pair.ts | 2 +-
src/structure/collections/iterator.ts | 52 +++++++++++++++------------
2 files changed, 31 insertions(+), 23 deletions(-)
diff --git a/src/structure/collections/int-pair.ts b/src/structure/collections/int-pair.ts
index 9e1bdd3c8..251b145cd 100644
--- a/src/structure/collections/int-pair.ts
+++ b/src/structure/collections/int-pair.ts
@@ -28,4 +28,4 @@ namespace IntPair {
}
}
-export default IntPair
+export default IntPair
\ No newline at end of file
diff --git a/src/structure/collections/iterator.ts b/src/structure/collections/iterator.ts
index 8dd89ed87..79fdbd0f9 100644
--- a/src/structure/collections/iterator.ts
+++ b/src/structure/collections/iterator.ts
@@ -5,64 +5,72 @@
*/
/**
- * ES6 compatible mutable iterator. Use with care.
+ * ES6 compatible iterator.
*
- * "Idiomatic" usage:
+ * "Idiomatic" usage is to use the move function, because it does not make any allocations.
*
* const it = ...;
- * for (let v = it.nextValue(); !it.done; v = it.nextValue()) { ... }
+ * for (let v = it.move(); it.hasNext; v = it.move()) { ... }
*/
interface Iterator<T> {
[Symbol.iterator](): Iterator<T>,
- readonly done: boolean,
- readonly value: T,
+ readonly hasNext: boolean,
next(): { done: boolean, value: T },
- nextValue(): T
+ move(): T
}
class ArrayIteratorImpl<T> implements Iterator<T> {
private xs: ArrayLike<T> = [];
private index: number = -1;
private length: number = 0;
+ private lastValue: T;
[Symbol.iterator]() { return this; };
- done = true;
- value: T = void 0 as any;
+ hasNext: boolean;
next() {
- const index = ++this.index;
- if (index < this.length) this.value = this.xs[index];
- else this.done = true;
- return this;
+ const value = this.move();
+ return { value, done: !this.hasNext };
}
- nextValue() { return this.next().value; }
+ move() {
+ const index = ++this.index;
+ if (index < this.length) this.lastValue = this.xs[index];
+ else this.hasNext = false;
+ return this.lastValue;
+ }
constructor(xs: ArrayLike<T>) {
this.length = xs.length;
- this.done = false;
+ this.hasNext = xs.length > 0;
this.xs = xs;
this.index = -1;
+ // try to avoid deoptimization with undefined values
+ this.lastValue = xs.length > 0 ? xs[0] : void 0 as any;
return this;
}
}
class RangeIteratorImpl implements Iterator<number> {
+ private value: number;
+
[Symbol.iterator]() { return this; };
- done = true;
- value: number;
+ hasNext: boolean;
next() {
- ++this.value;
- this.done = this.value > this.max;
- return this;
+ const value = this.value;
+ return { value, done: !this.hasNext }
}
- nextValue() { return this.next().value; }
+ move() {
+ ++this.value;
+ this.hasNext = this.value <= this.max;
+ return this.value;
+ }
constructor(min: number, private max: number) {
this.value = min - 1;
- this.done = false;
+ this.hasNext = max >= min;
return this;
}
}
@@ -75,7 +83,7 @@ namespace Iterator {
export function toArray<T>(it: Iterator<T>): T[] {
const ret = [];
- for (let v = it.nextValue(); !it.done; v = it.nextValue()) ret[ret.length] = v;
+ for (let v = it.move(); it.hasNext; v = it.move()) ret[ret.length] = v;
return ret;
}
}
--
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