PHP：awk的减法给指数值 [英] PHP : The awk subtraction giving exponential values

问题描述

我收到awk的结果，当我减去两个值，错​​误的是我得到2.7755575615629E-17指数值而不是0任何事情我错过申请，请建议。这与某些情况下发生的事情只有像0.66，0.67，0.33，

我使用下面给出的code的原型，

  $ _SESSION ['X​​'] = 1;
            $ _SESSION ['X​​'] = $ _SESSION ['X​​']  -  0.83;
            回波（$ _SESSION ['X​​']  -  0.17）;
            呼应'＆LT; BR＆GT;';
 

但在扭转值这一切都罚款0

  $ _SESSION ['X​​'] = 1;
            $ _SESSION ['X​​'] = $ _SESSION ['X​​']  -  0.17;
            回波（$ _SESSION ['X​​']  -  0.83）;
            呼应'＆LT; BR＆GT;';
 

解决方案

它是在计算机语言中一个共同的问题 - 浮点值没有被重新presented准确。另请参见 http://en.wikipedia.org/wiki/Floating_point#Accuracy_problems 。如果您有想正好与，你可以在PHP中使用 bcmath 函数计算出小数的特定量：

  $ _ SESSION ['X​​'] = 1;
$ _SESSION [X'] = bcsub（$ _ SESSION ['X​​']，0.83，10）;
回声bcsub（$ _ SESSION ['X​​']，0.17，10）;
呼应'＆LT; BR＆GT;';
 

否则，你可以简单地使用你的计算并添加圆（$结果，$ numberOfDecimalPlaces）为您计算结果。

I am getting awk result when I am subtracting two values, the error is I am getting exponent value 2.7755575615629E-17 instead of 0. Anything I am missing to apply, please suggest. These is happening with some cases only like 0.66, 0.67, 0.33,

The prototype of the code I am using is given below,

                    $_SESSION['x'] = 1;
            $_SESSION['x'] = $_SESSION['x'] - 0.83;
            echo ( $_SESSION['x']- 0.17) ;
            echo '<br>';

But on reversing the values It all fine with 0

                    $_SESSION['x'] = 1;
            $_SESSION['x'] = $_SESSION['x'] - 0.17;
            echo ( $_SESSION['x']- 0.83) ;
            echo '<br>';

解决方案

It is a common problem in computer languages - float values aren't represented exactly. See also http://en.wikipedia.org/wiki/Floating_point#Accuracy_problems. If you have a particular amount of decimal places you want to exactly calculate with, you can use the bcmath functions in PHP:

$_SESSION['x'] = 1;
$_SESSION['x'] = bcsub($_SESSION['x'], 0.83, 10);
echo bcsub($_SESSION['x'], 0.17, 10);
echo '<br>';

Otherwise you can simply use your calculation and add an round($result, $numberOfDecimalPlaces) to you calculated result.

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