From a07b2f9408feca0e000729be7e2a3bc17851b23b Mon Sep 17 00:00:00 2001
From: MiniPear <pearminipro@gmail.com>
Date: Fri, 18 Jun 2021 14:33:29 +0800
Subject: [PATCH] fix: pretty wilkinson-extended with precision problem close:
 #156 (#157)

* fix: pretty wilkinson-extended with precision problem close: #156

* chore: update test coverage

* chore: update version
---
 .../tick-methods/wilkinson-extended.spec.ts   |  7 ++++++-
 __tests__/unit/utils/add.spec.ts              | 13 ------------
 package.json                                  |  2 +-
 src/tick-methods/wilkinson-extended.ts        | 11 +++++++---
 src/utils/precision-add.ts                    | 20 -------------------
 5 files changed, 15 insertions(+), 38 deletions(-)
 delete mode 100644 __tests__/unit/utils/add.spec.ts
 delete mode 100644 src/utils/precision-add.ts

diff --git a/__tests__/unit/tick-methods/wilkinson-extended.spec.ts b/__tests__/unit/tick-methods/wilkinson-extended.spec.ts
index 8b29c527..1adf04bd 100644
--- a/__tests__/unit/tick-methods/wilkinson-extended.spec.ts
+++ b/__tests__/unit/tick-methods/wilkinson-extended.spec.ts
@@ -29,10 +29,15 @@ describe('wilkinson-extended test', () => {
     expect(wilkinsonExtended(0, 0.1, 5)).toStrictEqual([0, 0.025, 0.05, 0.075, 0.1]);
     expect(wilkinsonExtended(0, 0.01, 5)).toStrictEqual([0, 0.0025, 0.005, 0.0075, 0.01]);
     expect(wilkinsonExtended(0, 0.001, 5)).toStrictEqual([0, 0.00025, 0.0005, 0.00075, 0.001]);
-    expect(wilkinsonExtended(0, 0.0001, 6)).toStrictEqual([0, 0.00002, 0.00004, 0.00006, 0.00008, 0.0001]);
+    expect(wilkinsonExtended(0, 0.0001, 6)).toStrictEqual([0, 0.00002, 0.00004, 0.00006, 0.00008, 0.0001, 0.00012]);
     expect(wilkinsonExtended(0, 0.00001, 6)).toStrictEqual([
       0, 0.000002, 0.000004, 0.000006, 0.000008, 0.00001, 0.000012,
     ]);
     expect(wilkinsonExtended(0, 0.000001, 6)).toStrictEqual([0, 0.0000002, 0.0000004, 0.0000006, 0.0000008, 0.000001]);
+    expect(wilkinsonExtended(0, 1e-15, 6)).toStrictEqual([0, 2e-16, 4e-16, 6e-16, 8e-16, 1e-15]);
+  });
+
+  test('precision', () => {
+    expect(wilkinsonExtended(0, 1.2, 5)).toStrictEqual([0, 0.3, 0.6, 0.9, 1.2]);
   });
 });
diff --git a/__tests__/unit/utils/add.spec.ts b/__tests__/unit/utils/add.spec.ts
deleted file mode 100644
index 1e8093c1..00000000
--- a/__tests__/unit/utils/add.spec.ts
+++ /dev/null
@@ -1,13 +0,0 @@
-import { precisionAdd as fn } from '../../../src/utils/precision-add';
-
-describe('test precisionAdd', () => {
-  test('precisionAdd', () => {
-    expect(fn(0.1, 0.2)).toStrictEqual(0.3);
-    expect(fn(2.3, 2.4)).toStrictEqual(4.7);
-    expect(fn(-1.6, -1)).toStrictEqual(-2.6);
-    expect(fn(-2.0, 63)).toStrictEqual(61);
-    expect(fn(-3, 0.2)).toStrictEqual(-2.8);
-    expect(fn(1.3224e10, 1.3224e3)).toStrictEqual(13224001322.4);
-    expect(fn(1.6e-30, 1.6e-30)).toStrictEqual(3.2e-30);
-  });
-});
diff --git a/package.json b/package.json
index f50cd692..1db7d96c 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@antv/scale",
-  "version": "0.4.1",
+  "version": "0.4.2",
   "description": "Toolkit for mapping abstract data into visual representation.",
   "license": "MIT",
   "main": "lib/index.js",
diff --git a/src/tick-methods/wilkinson-extended.ts b/src/tick-methods/wilkinson-extended.ts
index b200d1ba..50596581 100644
--- a/src/tick-methods/wilkinson-extended.ts
+++ b/src/tick-methods/wilkinson-extended.ts
@@ -1,6 +1,5 @@
 import { indexOf, size } from '@antv/util';
 import { TickMethod } from '../types';
-import { precisionAdd } from '../utils/precision-add';
 
 export const DEFAULT_Q = [1, 5, 2, 2.5, 4, 3];
 
@@ -61,6 +60,11 @@ function legibility() {
   return 1;
 }
 
+// 为了解决 js 运算的精度问题
+function pretty(n: number) {
+  return n < 1e-15 ? n : parseFloat(n.toFixed(15));
+}
+
 /**
  * An Extension of Wilkinson's Algorithm for Position Tick Labels on Axes
  * https://www.yuque.com/preview/yuque/0/2019/pdf/185317/1546999150858-45c3b9c2-4e86-4223-bf1a-8a732e8195ed.pdf
@@ -165,9 +169,10 @@ export const wilkinsonExtended: TickMethod = (
   // 步长为浮点数时处理精度
   const range = new Array(Math.floor(size));
 
-  for (let tick = best.lmin; tick <= best.lmax; tick = precisionAdd(tick, best.lstep)) {
-    range[i] = tick;
+  for (let tick = best.lmin; tick <= best.lmax; tick += best.lstep) {
+    range[i] = pretty(tick);
     i += 1;
   }
+
   return range;
 };
diff --git a/src/utils/precision-add.ts b/src/utils/precision-add.ts
deleted file mode 100644
index 6ed31902..00000000
--- a/src/utils/precision-add.ts
+++ /dev/null
@@ -1,20 +0,0 @@
-function digitLength(num: number) {
-  // Get digit length of e
-  const eSplit = num.toString().split(/[eE]/);
-  const len = (eSplit[0].split('.')[1] || '').length - +(eSplit[1] || 0);
-  return len > 0 ? len : 0;
-}
-
-/**
- * 高精度加法，解决 0.1 + 0.2 !== 0.3 的经典问题
- *
- * @param num1 加数
- * @param num2 被加数
- * @return {number} 返回值
- */
-export function precisionAdd(num1: number, num2: number) {
-  const num1Digits = digitLength(num1);
-  const num2Digits = digitLength(num2);
-  const baseNum = 10 ** Math.max(num1Digits, num2Digits);
-  return (num1 * baseNum + num2 * baseNum) / baseNum;
-}