Question

I would like to know if there’s a “widely accepted” naming convention in C++ when writing such methods:

class Transform3d {
public: 
    // Apply rotation using a copy of toRotate and return it  
    Vector3d ApplyRotation(const Vector3d& toRotate) const;

    // Apply rotation directly to toRotate 
    void ApplyRotationInPlace(Vector3d& toRotate) const;

    // Apply rotation on this Transform3d instance (orientation quat)
    void ApplyRotation(const Vector3d& toRotate); 

   //...

    // Apply transformation using a copy of toTransform and return it 
    Transform3d ApplyTransform(const Vector3d& toTransform) const;

    // Apply transformation directly to toTransform
    void ApplyTransformInPlace(Vector3d& toTransform) const;

private:
    Quaternion orientation;
    Vector3d position;
};

Is there some guidelines for writing C++ method which deals with parameters modification and return new instance (with no modification on the parameter) ?

Answer 1

Yes, and you stumbled upon it. It’s the const modifiers.

Is there some guidelines for writing C++ method which deals with
parameters modification and return new instance (with no modification
on the parameter) ?

By marking your parameters const, that’s exactly what you guarantee. const is really there for the developers.