在C#中使用float计算财务价值的问题 [英] Issue with calculating financial values using float in C#

问题描述

我正在阅读一篇有关Float和double的区别的文章.他们给出了一个示例，如下所示:

I was reading an article related to difference between Float and double. and they given an example as below :

假设您有一件$ 100的商品，并给您10％的折扣.您的价格全为美元，因此您可以使用int变量存储价格.这是您得到的:

Say you have a $100 item, and you give a 10% discount. Your prices are all in full dollars, so you use int variables to store prices. Here is what you get:

int fullPrice = 100;
float discount = 0.1F;
Int32 finalPrice = (int)(fullPrice * (1-discount));
Console.WriteLine("The discounted price is ${0}.", finalPrice);

猜猜看:最终价格是89美元，而不是预期的90美元.您的客户会很高兴，但您不会.您给了他们1％的额外折扣.

Guess what: the final price is $89, not the expected $90. Your customers will be happy, but you won't. You've given them an extra 1% discount.

在上面的示例中，他们使用fullPrice * (1-discount)来计算最终价格.他们为什么使用(1-disocunt)?应该是fullPrice * discount.

In above example, to calculate the final price they have used fullPrice * (1-discount) . why they used (1-disocunt) ? it should be fullPrice * discount.

所以我的困惑在于计算最终价格的逻辑.为什么thay使用(1-discount)而不是discount?

so my confusion is about logic to calculate the final price. why thay used (1-discount) instead of discount ?

推荐答案

最终价格为89美元，而不是预期的90美元

the final price is $89, not the expected $90

这是因为，当0.1是float时，它不完全是0.1，而是更多.从1减去它进行数学运算时，得到$89.9999998509884.强制转换为int会将结果截断为89(演示).

That's because when 0.1 is float, it is not exactly 0.1, it's a little more. When you subtract it from 1 to do the math, you get $89.9999998509884. Casting to int truncates the result to 89 (demo).

您可以通过使用decimal数据类型进行打折来实现此目的.此类型可以表示0.1而不会造成精度损失(演示).

You can make this work by using decimal data type for your discount. This type can represent 0.1 without a precision loss (demo).

为什么使用(1-disocunt)

1表示100％.折后价为(100％-10％)= 90％

1 represents 100%. The price after discount is (100%-10%)=90%

这篇关于在C#中使用float计算财务价值的问题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！