使用boost :: numeric_cast＆LT;＆GT; [英] Using boost::numeric_cast<>

问题描述

当我想不同的整数类型之间的转换，这似乎是最好的语法是使用的boost :: numeric_cast＆LT;＆GT;（）：

When I want to convert between different integer types, it seems the best syntax is to use boost::numeric_cast<>():

int y = 99999;
short x = boost::numeric_cast<short>(y); // will throw an exception if y is too large

我从来没有使用的;然而，语法是pretty简单易懂，所以一切都很好。

I have never used that; however the syntax is pretty straightforward, so all is well.

现在假设我希望做一些更高级的：不是抛出一个异常，我想它返回目标类型（饱和度）的最小或最大。我无法想出一个办法来恩preSS的，但是的文档表明，它是可能的（可能使用 RawConverter 策略）。所有我能想出如下丑：

Now suppose I want to do something a bit more advanced: instead of throwing an exception, I'd like it to return the min or max of the target type (saturation). I couldn't figure out a way to express that, but the documentation suggests that it is possible (probably using RawConverter policy). All I could come up with is the following ugly:

short x = numeric_cast<short>(max(min(y, SHORT_MAX), SHORT_MIN);

所以，我怎么能前preSS饱和投使用boost的 numeric_cast ？

推荐答案

您也许可以做这样的事情：

You could probably do something like this:

#include <limits>

template<typename Target, typename Source>
Target saturation_cast(Source src) {
   try {
      return boost::numeric_cast<Target>(src);
   }
   catch (const boost::negative_overflow &e) {
      return std::numeric_limits<Target>::lowest();
      /* Or, before C++11:
      if (std::numeric_limits<Target>::is_integer)
         return std::numeric_limits<Target>::min();
      else
         return -std::numeric_limits<Target>::max();
      */
   }
   catch (const boost::positive_overflow &e) {
      return std::numeric_limits<Target>::max();
   }
}

（对于支持它的错误情况类型也可以返回-INF / + INF）。

(For types that support it the error cases could also return -inf/+inf).

这样，你让Boost的 numeric_cast 确定该值超出范围，然后就可以做出相应的反应。

This way you let Boost's numeric_cast determine if the value is out of bounds and can then react accordingly.

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