问题描述

例子:

float timeRemaining = 0.58f;

为什么这个数字的末尾需要f?

Why is the f is required at the end of this number?

推荐答案

你的浮点声明包含两部分:

Your declaration of a float contains two parts:

1. 它声明变量timeRemaining的类型是float.
2. 它将值 0.58 分配给该变量.

1. It declares that the variable timeRemaining is of type float.
2. It assigns the value 0.58 to this variable.

问题出现在第 2 部分.

The problem occurs in part 2.

右侧是自行评估的.根据 C# 规范，包含没有后缀的小数点的数字被解释为 double.

The right-hand side is evaluated on its own. According to the C# specification, a number containing a decimal point that doesn't have a suffix is interpreted as a double.

所以我们现在有一个 double 值，我们希望将其分配给 float 类型的变量.为了做到这一点，必须有一个从 double 到 float 的隐式转换.没有这样的转换，因为您可能(并且在这种情况下确实)在转换中丢失了信息.

So we now have a double value that we want to assign to a variable of type float. In order to do this, there must be an implicit conversion from double to float. There is no such conversion, because you may (and in this case do) lose information in the conversion.

原因是编译器使用的值并不是真正的 0.58，而是最接近 0.58 的浮点值，即 double 为 0.57999999999999978655962351581366... 而 恰好为 0.579999946057796478271484375>浮动.

The reason is that the value used by the compiler isn't really 0.58, but the floating-point value closest to 0.58, which is 0.57999999999999978655962351581366... for double and exactly 0.579999946057796478271484375 for float.

严格来说，f 不是必需的.您可以通过将值转换为 float 来避免使用 f 后缀:

Strictly speaking, the f is not required. You can avoid having to use the f suffix by casting the value to a float:

float timeRemaining = (float)0.58;

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