From 6f1f3b24c9c21311ff33e7d4b987b40c6b304e04 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tobias=20Nie=C3=9Fen?= <tniessen@tnie.de>
Date: Wed, 25 Aug 2021 01:19:35 +0000
Subject: [PATCH] Avoid propagating rounding errors in linearBuckets

---
 CHANGELOG.md                 | 5 +++++
 lib/bucketGenerators.js      | 3 +--
 test/bucketGeneratorsTest.js | 5 +++++
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 864a1a76..b6e3588d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,11 @@ project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Breaking
 
+- changed: `linearBuckets` does not propagate rounding errors anymore.
+
+  Fewer bucket bounds will be affected by rounding errors. Histogram bucket
+  labels may change.
+
 ### Changed
 
 ### Added
diff --git a/lib/bucketGenerators.js b/lib/bucketGenerators.js
index ddd51dfc..a9a487c7 100644
--- a/lib/bucketGenerators.js
+++ b/lib/bucketGenerators.js
@@ -7,8 +7,7 @@ exports.linearBuckets = (start, width, count) => {
 
 	const buckets = new Array(count);
 	for (let i = 0; i < count; i++) {
-		buckets[i] = start;
-		start += width;
+		buckets[i] = start + i * width;
 	}
 	return buckets;
 };
diff --git a/test/bucketGeneratorsTest.js b/test/bucketGeneratorsTest.js
index 5f8d5860..898be657 100644
--- a/test/bucketGeneratorsTest.js
+++ b/test/bucketGeneratorsTest.js
@@ -27,6 +27,11 @@ describe('bucketGenerators', () => {
 			};
 			expect(fn).toThrowError(Error);
 		});
+
+		it('should not propagate rounding errors', () => {
+			result = linearBuckets(0.1, 0.1, 10);
+			expect(result[9]).toEqual(1);
+		});
 	});
 
 	describe('exponential buckets', () => {