什么是表达模板数字文字的最好方法？ [英] What is the best way to express a templated numeric literal?

问题描述

我有一个函数可以减少到这样的：

  template< class T& 
 T foo（T x）
 {
 return 123.45 / x; 
} 
  

我想确保数字文字1​​23.45与x 。让我们假设T可以是任何数字类型：signed / unsigned char to long-long或float to long-double。

123.45应该是T类型

我的要求

• 不应发出警告（每打开一个警告）。


• 我希望十进制数123.45在计算中使用的精度为T

我想要达到这些目标的最优雅的解决方案。

• 旧式铸造，即（T）123.45 在C ++中基本上已弃用。


• static_cast< T>（123.45）


• 我不确定是否有后缀（例如 123.45L ）是必要的，以便在T long double 的情况下获得最大精度，或者编译器将自动使用最高精度的十进制到二进制转换。

更新5-7-2014

在我的代码库中将数百个转换改变为 T（123.45）后，我发现有时候这种语法不可用。例如，你不能做 long double（123.45），因为C ++不支持multitoken类型构造函数。在这些情况下，我选择了 static_cast< long double>（123.45）。

解决方案

简单的

 模板< class T> 
 T foo（T x）
 {
 return T（123.45）/ x; 
} 
  

这将允许自定义数值类接受构造函数中的值。 p>

I have a function that could be reduced to something like this:

template<class T>
T foo(T x)
{
  return 123.45 / x;
}

I would like to ensure that the numeric literal 123.45 is the same type as x. Let's say that T could be any numeric type: signed/unsigned char to long-long or float to long-double.

What is the most modern way to indicate that 123.45 should be of type T?

My requirements

• No warnings should be emitted (with every warning turned on).
• I want the decimal number 123.45 to have the precision of T when used in the calculation.
• I want the most elegant solution that achieves these goals.

Issues under consideration

• The “old-style cast”, i.e. (T)123.45 is essentially deprecated in C++.
• static_cast<T>(123.45) seems like the right type of cast. However, it is verbose, and I have never seen this used on a literal.
• I am unsure if a suffix (e.g. 123.45L) is necessary in order to get the maximum precision in the case of T being long double, or if the compiler will automatically use the highest precision decimal-to-binary conversion.

Update 5-7-2014

After changing hundreds of casts in my codebase to the form T(123.45), I found that there are times when this syntax is unavailable. For example, you can not do long double(123.45) because C++ does not support multitoken type constructors. In these cases, I have opted for static_cast<long double>(123.45).

解决方案

What about a simple

template<class T>
T foo(T x)
{
  return T(123.45) / x;
}

which will allow custom numeric classes to accept the value in a constructor.

这篇关于什么是表达模板数字文字的最好方法？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！