code: func (v Vec) ApproxFuncEqual(v2 Vec, eq func(float64, float64) bool) bool {
  	if !eq(v.X, v2.X) {
  		return false
  	}
  	if !eq(v.Y, v2.Y) {
  		return false
  	}
  	return true
  }
docs: // ApproxFuncEqual takes in a func that compares two floats, and uses it to do
  // an element-wise comparison of the vector to another.
  //
  // This is intended to be used with FloatEqualFunc