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

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

#include <algorithm>
//...

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

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

largestDeviation =

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

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);

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);

#include <algorithm>

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

// 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));
}