Is there a way to dynamically change a comparison operator?-CodePudding

I'm creating an AI Director and need a way to change when the AI needs to pressure the player and when they need to move away. I've got a TArray of Objects and am checking the distance from the player. I'd like to either get the largest distance or the smallest distance.

I know this doesn't work:

operator comparer = PlayerTensionLevel > BackstageThreshold ? > : <;

Both of the variables used in the one line Bool are floats. I'm hoping that the comparer can be used in a situation like:

if(DistanceSquared(objectA, objectB) comparer _currentThresholdDistance){
    _currentObject = objectA;
    _currentThresholdDistance = DistanceSquared(objectA, objectB);
}

CodePudding user response：

You can compute with bool! If you aren’t concerned with differing behavior for ties, you can just write

if((DistanceSquared(objectA, objectB) > _currentThresholdDistance) ==
   (PlayerTensionLevel > BackstageThreshold)) …

(Technically, the extra parentheses here are unnecessary, but it’s probably not reasonable to expect the reader to know that relational operators have higher precedence than equality operators.)

CodePudding user response：

As already mentioned in @SamVarshavchik's comment above,
You can use std::function and assign it to either std::less or std::greater based on PlayerTensionLevel and BackstageThreshold.

After you determine the comparator you can use it against the current values of _currentThresholdDistance and the the squared distance between the objects (here I just used dist2 to represent it).

#include <iostream>
#include <functional>

std::function<bool(double a, double b)> 
        GetComp(double PlayerTensionLevel, double BackstageThreshold)
{
    if (PlayerTensionLevel > BackstageThreshold) {
        return std::less<double>{};
    }
    return std::greater<double>{};
}

int main() {
    double _currentThresholdDistance = 1;
    double dist2 = 2;

    double PlayerTensionLevel = 100;
    double BackstageThreshold;

    BackstageThreshold = 101;
    std::cout << GetComp(PlayerTensionLevel, BackstageThreshold)  
                        (dist2, _currentThresholdDistance) << std::endl;

    BackstageThreshold = 99;
    std::cout << GetComp(PlayerTensionLevel, BackstageThreshold)
                        (dist2, _currentThresholdDistance) << std::endl;
}

Output:

1
0