C ++中用于在数字类型之间进行转换的最佳实践

Best practice in C++ for casting between number types

本问题已经有最佳答案，请猛点这里访问。

在不同的数字类型之间进行转换的最佳实践是什么？EDCX1、0、EDCOX1、1、EDCX1、2是我在C++中使用最多的类型。

其中f是float和n是double或int的期权示例：

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float f = static_cast<float>(n);
float f = float(n);
float f = (float)n;

我通常写EDCOX1，8，但是如果有一个优选的方式，在C++开发社区内是否有任何共识。

我很感激这可能是一个基于意见的问题，可能没有"标准"的方式，在这种情况下，请让我知道没有标准的方式，所以至少我知道：

我知道这个问题出现在一般的铸造方面，但是，我特别感兴趣的是数字，以及在数字类型的方法中是否有特定的最佳实践。

相关讨论

只需使用static_cast。C类型转换的问题在于操作的模糊性(即显式类型转换的点(1))。

C++避免了这一点。另外，C++搜索在搜索它们时更为明显。

使用stroustrup的话(静态广播有什么好处？)：

Even an innocent-looking cast can become a serious problem if, during development or maintenance, one of the types involved is changed. For example, what does this mean?:

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x = (T)y;

We don't know. It depends on the type T and the types of x and y. T could be the name of a class, a typedef, or maybe a template parameter. Maybe x and y are scalar variables and (T) represents a value conversion. Maybe x is of a class derived from y's class and (T) is a downcast. Maybe x and y are unrelated pointer types. Because the C-style cast (T) can be used to express many logically different operations, the compiler has only the barest chance to catch misuses. For the same reason, a programmer may not know exactly what a cast does. This is sometimes considered an advantage by novice programmers and is a source of subtle errors when the novice guessed wrong.

The"new-style casts" were introduced to give programmers a chance to state their intentions more clearly and for the compiler to catch more errors.

[CUT]

A secondary reason for introducing the new-style cast was that C-style casts are very hard to spot in a program. For example, you can't conveniently search for casts using an ordinary editor or word processor.

[CUT]

casts really are mostly avoidable in modern C++

还可以考虑作为更安全的替代方案(boost.numericconversion库的一部分)的boost::numeric::converter/boost::numeric_cast。

例如。

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#include <iostream>
#include <boost/numeric/conversion/cast.hpp>

int main()
{
using boost::numeric_cast;

using boost::numeric::bad_numeric_cast;
using boost::numeric::positive_overflow;
using boost::numeric::negative_overflow;

try
{
int i = 42;
short s = numeric_cast<short>(i); // This conversion succeeds (is in range)
}
catch(negative_overflow &e) { std::cout << e.what(); }
catch(positive_overflow &e) { std::cout << e.what(); }

return 0;
}

一般来说，对于隐式转换和显式转换(通过static_cast转换)，缺少保留的范围使数值类型之间的转换容易出错。

numeric_cast在转换数字类型时检测到范围丢失，如果无法保留该范围，则抛出异常。

相关讨论

一般来说，这些铸造操作员分为两大类：具体铸造操作人员和传统铸造操作人员。cplusplus.com这样解释：

...In order to control these types of conversions between classes, we have four specific casting operators: dynamic_cast, reinterpret_cast, static_cast and const_cast. Their format is to follow the new type enclosed between angle-brackets (<>) and immediately after, the expression to be converted between parentheses.

dynamic_cast (expression)

reinterpret_cast (expression)

static_cast (expression)

const_cast (expression)

The traditional type-casting equivalents to these expressions would be:

(new_type) expression

new_type (expression)

but each one with its own special characteristics.

在处理任务时，我们(几乎)都使用特定的强制转换。在考虑了这些建议之后，不知何故，这取决于你。

查看资源。