Question

我有这段代码：

largestDeviation = max(max(max(angleBetweenVectors(robustNormal, normalAtA),
                               angleBetweenVectors(robustNormal, normalAtB)),
                           angleBetweenVectors(robustNormal, normalAtC)),
                       angleBetweenVectors(robustNormal, normalAtD)),
                       angleBetweenVectors(robustNormal, normalAtE);

方法：angleBetweenVectors返回float。

我看不出这段代码在做什么以及为什么它正在构建，括号不能正确匹配，我担心它会导致错误。如何才能获得angleBetweenVectors所有来电的最大价值？

Answer 1

添加一些修改，你会得到：

largestDeviation = 
max(
   max(
      max(
         angleBetweenVectors(robustNormal, normalAtA),
         angleBetweenVectors(robustNormal, normalAtB)
      ),
      angleBetweenVectors(robustNormal, normalAtC)
   ),
   angleBetweenVectors(robustNormal, normalAtD)
), 
angleBetweenVectors(robustNormal, normalAtE);

即。它将返回angleBetweenVectors(robustNormal, normalAtE);的值，因为您缺少max

Answer 2

您可以使用标准算法std :: max作为参数std::initializer_list 例如

#include <algorithm>
//...

largestDeviation = std::max(
{
   angleBetweenVectors( robustNormal, normalAtA ), 
   angleBetweenVectors( robustNormal, normalAtB ),
   angleBetweenVectors( robustNormal, normalAtC ), 
   angleBetweenVectors( robustNormal, normalAtD ), 
   angleBetweenVectors( robustNormal, normalAtE )
} );

对于您的代码，它确定函数angleBetweenVectors的相应调用返回的值中的最大值。该代码使用标准算法std::max，它具有两个参数并确定两个参数之间的最大值。

例如内部调用

max( angleBetweenVectors(robustNormal, normalAtA ),
     angleBetweenVectors(robustNormal, normalAtB ) ),

查找函数调用返回的两个值之间的最大值。如果函数依次用于封闭式std::max调用，则函数std::max的结果以及下一次调用。

顺便说一句，你的代码有编译错误。应该再调用std::max

largestDeviation = 

max(
   max(
      max(
         max( angleBetweenVectors(robustNormal, normalAtA ),
              angleBetweenVectors(robustNormal, normalAtB) 
         ),
         angleBetweenVectors(robustNormal, normalAtC)
      ),
      angleBetweenVectors(robustNormal, normalAtD) 
   ),
   angleBetweenVectors(robustNormal, normalAtE)
);

Answer 3

您也可以像这样编写代码：

maxAngle = angleBetweenVectors(robustNormal, normalAtA);
maxAngle = max(angleBetweenVectors(robustNormal, normalAtB), maxAngle);
maxAngle = max(angleBetweenVectors(robustNormal, normalAtC), maxAngle);
maxAngle = max(angleBetweenVectors(robustNormal, normalAtD), maxAngle);
maxAngle = max(angleBetweenVectors(robustNormal, normalAtE), maxAngle);

或者，在为maxAngle选择良好的初始值时更加一致，例如我会说-2*M_PI：

maxAngle = -2 * M_PI;
maxAngle = max(angleBetweenVectors(robustNormal, normalAtA), maxAngle);
maxAngle = max(angleBetweenVectors(robustNormal, normalAtB), maxAngle);
maxAngle = max(angleBetweenVectors(robustNormal, normalAtC), maxAngle);
maxAngle = max(angleBetweenVectors(robustNormal, normalAtD), maxAngle);
maxAngle = max(angleBetweenVectors(robustNormal, normalAtE), maxAngle);

Answer 4

<强> C ++ 11

#include <algorithm>

largestDeviation = std::max({
   angleBetweenVectors(robustNormal, normalAtA),
   angleBetweenVectors(robustNormal, normalAtB),
   angleBetweenVectors(robustNormal, normalAtC),
   angleBetweenVectors(robustNormal, normalAtD),
   angleBetweenVectors(robustNormal, normalAtE)
});

Answer 5

// Store all your normals in a vector
std::vector<normal> normals;
normals.push_back(normalAtA);
normals.push_back(normalAtB);
normals.push_back(normalAtC);
normals.push_back(normalAtD);
normals.push_back(normalAtE);

// Iterate through your vector, and check each angle to see if it is the new max
max_val = 0;
vector<normal>::iterator it;
for (it = normals.begin(); it != normals.end(); ++it)
{
    max_val = max(max_val, angleBetweenVectors(robustNormal, *it));
}

使用max函数的奇怪行为

5 个答案: