函数“包含"的基本用法包括:在Boost ICL中:是否未实现间隔类型和函数的某些组合?

问题描述

我开始使用Boost ICL，偶然发现了非常基本的东西.例如，函数contains应该返回true或false，这取决于给定元素是否在间隔中.但这对[right,left]_open_intervals有效，但对[open,closed]_inteval无效(请参见下面的示例).

I started to use Boost ICL and I stumbled upon very basic stuff. For example the function contains should return true or false depending if a given element is in the interval or not. However that works for [right,left]_open_intervals but not for [open,closed]_inteval (see example below).

这似乎太明显了，不能忽略.我正在按预期方式使用图书馆吗?

例如(使用gcc 4.8或clang 3.3和Boost 1.54):

For example (using gcc 4.8 or clang 3.3 and Boost 1.54):

#include <boost/concept_check.hpp> //needed to make this MWE work, boost icl should include it internally

#include<boost/icl/right_open_interval.hpp>
#include<boost/icl/closed_interval.hpp>
#include<boost/icl/open_interval.hpp>
int main(){
    boost::icl::right_open_interval<double> roi(6.,7.);
    assert(boost::icl::contains(roi, 6.) == true);  //ok
    assert(boost::icl::contains(roi, 6.) == false); //ok

    boost::icl::closed_interval<double> oi(4.,5.); // or open_interval
    assert(boost::icl::contains( oi, 4.) == false); //error: "candidate template ignored"
    assert(boost::icl::contains( oi, 5.) == false); //error: "candidate template ignored"
}

注意:上面的被称为静态"间隔(因为它们的绑定属性是该类型的一部分).动态间隔按预期工作.

Note: The above are called "static" intervals (because their bound properties are part of the type). Dynamic intervals work as expected.

推荐答案

我想这可以归结为浮点相等测试的相对无用性.

I would guess it comes down to the relative uselessness of floating point equality testing.

您曾经尝试过assert(0.1 + 0.2 == 0.3)吗?

尝试一下.我会等待.

如果您已经知道答案，那么很清楚为什么封闭间隔不容易正确实现.背景资料:

In case you already know the answer, it'll be clear why a closed interval is not easy to implement correctly. Backgrounders:

• 浮点数学运算是否被破坏?
• 为什么GCC无法优化a * a * a * a * a * a到(a * a * a)*(a * a * a)?
• 每个程序员应了解的浮点算法

• Is floating point math broken?
• Why doesn't GCC optimize a*a*a*a*a*a to (a*a*a)*(a*a*a)?
• What Every Programmer Should Know About Floating-Point Arithmetic

此外，如果您有两个连续的关闭时间间隔[a,b][b,c]. b属于哪个间隔?

Also, if you have two consecutive closed intervals [a,b][b,c]. in which interval does b belong?

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