Dynamic reconfigure in ROS 1 allows to define a lower / upper bound for numeric parameters. That information enables more usable UI elements like sliders.

While the logic to check if a specific parameter can be arbitrary complex narrowing the valid numeric values with a lower / upper bound already covers many use cases. Therefore the ParameterDescriptor should be extended to add this information.

For integer parameters obviously integer boundaries would be fitting. For floating point number the boundaries should be floating point numbers though in order to e.g. express a range [0, pi].

Since any fields are part of the message independent of the actual parameter type adding multiple different boundaries for each type isn't appealing since it increases the message size.

Therefore I propose to add lower and upper bounds with a floating point type. It enables the precise range necessary for floating point parameters and for integer parameters the conventions could be to round to the closest integer.

I am looking for early feedback on this so that the implementation can start beginning of next week.