为什么我看到在ECMAScript中/ ActionScript 3的不精确浮点运算的结果吗？ [英] Why am I seeing inexact floating-point results in ECMAScript / ActionScript 3?

问题描述

嘿，让我们直接跳转到一个code示例来说明如何的ECMAScript / JavaScript的/ AS3不能做简单的数学向右（AS3采用了IEEE-754双precision浮点数对于按理说它是相同的，在JavaScript中使用的数量级）

Hey all, let's jump straight to a code sample to show how ECMAScript/JavaScript/AS3 can't do simple math right (AS3 uses a 'IEEE-754 double-precision floating-point number' for the Number class which is supposedly identical to that used in JavaScript)...

trace(1.1);         //'1.1': Ok, fine, looks good.
trace(1.1*100);     //'110.00000000000001': What!?
trace((1.1*100)/100);  //'1.1': Brings it back to 1.1 (since we're apparently multiplying by *approximately* 100 and then dividing by the same *approximate* '100' amount)
trace(1.1*100-110); //'1.4210854715202004e-14': Proof that according to AS3, 1.1*100!=110 (i.e. this isn't just a bug in Number.toString())
trace(1.1*100==110);   //'false': Even further proof that according to AS3, 1.1*100!=110

怎么办？

推荐答案

欢迎来到奇妙世界的浮点运算精度。在一般情况下，浮点计算会给你一点效果都非常非常接近正确的，但比较输出为绝对平等是不可能给你结果你期望在不使用四舍五入功能。

Welcome to the wonderful world of floating point calculation accuracy. In general, floating point calculations will give you results that are very very nearly correct, but comparing outputs for absolute equality is unlikely to give you results you expect without the use of rounding functions.

这篇关于为什么我看到在ECMAScript中/ ActionScript 3的不精确浮点运算的结果吗？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！