From 210dd0da67d209773f2dae5a0751cc15f23dec31 Mon Sep 17 00:00:00 2001
From: "lixuefei.1313" <lixuef1313@163.com>
Date: Thu, 7 Sep 2023 11:34:14 +0800
Subject: [PATCH] feat: support precision math of add & sub

---
 packages/vutils/__tests__/math/math.test.ts | 10 ++++++++++
 packages/vutils/src/math.ts                 | 14 ++++++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 packages/vutils/__tests__/math/math.test.ts

diff --git a/packages/vutils/__tests__/math/math.test.ts b/packages/vutils/__tests__/math/math.test.ts
new file mode 100644
index 0000000..caae468
--- /dev/null
+++ b/packages/vutils/__tests__/math/math.test.ts
@@ -0,0 +1,10 @@
+import { precisionAdd, precisionSub } from '../../src/math';
+
+describe('precision', () => {
+  it('precision add', () => {
+    expect(precisionAdd(0.1, 0.2)).toBe(0.3);
+  });
+  it('precision sub', () => {
+    expect(precisionSub(33, 23.33)).toBe(9.67);
+  });
+});
diff --git a/packages/vutils/src/math.ts b/packages/vutils/src/math.ts
index fe86ca7..816253e 100644
--- a/packages/vutils/src/math.ts
+++ b/packages/vutils/src/math.ts
@@ -117,3 +117,17 @@ export function fuzzyEqualVec(a: vec2, b: vec2): boolean {
 export function fixPrecision(num: number, precision = 10) {
   return Math.round(num * precision) / precision;
 }
+
+export function getDecimalPlaces(n: number): number {
+  const dStr = n.toString().split(/[eE]/);
+  const s = (dStr[0].split('.')[1] || '').length - (+dStr[1] || 0);
+  return s > 0 ? s : 0;
+}
+
+export function precisionAdd(a: number, b: number) {
+  return fixPrecision(a + b, Math.pow(10, Math.max(getDecimalPlaces(a), getDecimalPlaces(b))));
+}
+
+export function precisionSub(a: number, b: number) {
+  return fixPrecision(a - b, Math.pow(10, Math.max(getDecimalPlaces(a), getDecimalPlaces(b))));
+}