浮点比较STL，BOOST [英] Floating point comparison in STL, BOOST

问题描述

在STL或Boost中有一组通用的简单比较函数吗？

我发现的一个总是需要模板参数，和/或实例化一个
结构模板。

我正在寻找类似以下语法的内容：

  if（is_equal（x，y））
 {
 ... 
} 
  

可以这样实现：

  template< typename T> 
 bool is_equal（const T& x，const T& y）
 {
 return（fabs（x-y）< Precision< T> :: eps）; 
} 
  

编辑：我将运算符更改为相等。 （见下面的注释）

解决方案

我不知道有任何库可以这么做，也许是因为它像一个简单的单线或可能是因为它被遗忘...

一般情况下，你确定你想设置一个给定类型的epsilon给定的价值...整个应用程序？就我个人而言，我想根据自己所做的操作对其进行自定义（即使默认设置会很好）。

至于您的操作员，为什么不自己设计？

 模板< class T> 
 bool rough_eq（T lhs，T rhs，T epsilon = Precision T :: epsilon）// operator == 
 {
 return fabs（lhs -rhs）小量; 
} 
 
模板< class T> 
 bool rough_lt（T lhs，T rhs，T epsilon = Precision< T>ε）//运算符< 
 {
 return rhs  -  lhs> = epsilon; 
 // tricky> =因为如果差值等于epsilon 
 //那么它们就不是每个rough_eq方法都相等
} 
 
 template< class T> 
 bool rough_lte（T lhs，T rhs，T epsilon = Precision T ::ε）//运算符< = 
 {
 return rhs -lhs> -epsilon; 
 
 $ / code> 

不等式和大于方法可以由此得到平凡的结果。 >



附加参数意味着您可能希望为给定的一组计算指定另一个值...应用程序范围的设置过于严格。


Is there in the STL or in Boost a set of generic simple comparison functions?

The one I found are always requiring template parameters, and/or instantiation of a struct template.

I'm looking for something with a syntax like :

if ( is_equal(x,y) )
{
   ...
}

Which could be implemented as :

template <typename T>
bool is_equal(const T& x, const T& y)
{
    return ( fabs(x - y) < Precision<T>::eps );
}

EDIT: I changed the operator to equal. (see comments below)

解决方案

I don't know of any library that does it, perhaps because it is as simple as a one-liner or perhaps because it was forgotten...

As generality goes though, are you sure you'd like to set up the epsilon for one given type at a given value... throughout the application ? Personally I'd like to customize it depending on the operations I am doing (even though a default would be nice).

As for your operators, why not devising them yourself ?

template <class T>
bool rough_eq(T lhs, T rhs, T epsilon = Precision<T>::epsilon) // operator==
{ 
  return fabs(lhs - rhs) < epsilon;
}

template <class T>
bool rough_lt(T lhs, T rhs, T epsilon = Precision<T>::epsilon) // operator<
{
  return rhs - lhs >= epsilon;
       // tricky >= because if the difference is equal to epsilon
       // then they are not equal per the rough_eq method
}

template <class T>
bool rough_lte(T lhs, T rhs, T epsilon = Precision<T>::epsilon) // operator<=
{
  return rhs - lhs > -epsilon;
}

The inequality and greater than methods can be trivially derived from this.

The additional parameter means that you may wish to specify another value for a given set of computations... an application-wide setting is too strict.

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