Addition and subtraction of time profiles

[trulsf]

Initial attempt at better support for addition and subtraction of time profiles (see #91).

There is still some open questions to be discussed.

• Should there be more explicit errors for addition of profiles not supported (e.g. ScenarioProfile + RepresentativeProfile) or should we make the effort to support all combinations?
• Should arithmetic support also be extended to StrategicStochasticProfile?

There is also the question about changing the behavior of what to do when using too short profiles for a time structure. Should we return an error instead of repeating the last, as we do today? This will be a breaking change so I think we should consider it for a separate PR.

[JulStraus]

• Should there be more explicit errors for addition of profiles not supported (e.g. ScenarioProfile + RepresentativeProfile) or should we make the effort to support all combinations?
• Should arithmetic support also be extended to StrategicStochasticProfile?

Regarding your two points above, I would say that we should support all TimeProfiles, including StrategicStochasticProfile and ad also support for ScenarioProfile + RepresentativeProfile in practice, we can easily have a ScenarioProfile within a RepresentativeProfile. I am however a bit skeptical whether people do not anyhow run in errors if they want to try it out.

I do not really think that we have to be more explicit with respect to an error message in a first step. Currently, we do not advertise the potential of adding two individual profiles, so people working with it should have a good understanding of their profiles.

The only problem I see is if some of the sub profiles do not have the same length. In this case, we would need to track the specific index if we plan to provide a reasonable answer. That would however increase the overhead quite a bit, so I would refrain from it.

Regarding your last point: I would be in favor of removing it entirely. It can lead to a weird behavior, especially with OperationalProfile. But as you mention, that is for another PR as it would be breaking. We could introduce it into Milestone 1.

[JulStraus]

Looks good to me.

In the current stage, we still only support, e.g., StrategicProfile + OperationalProfile and StrategicProfile + FixedProfile but not StrategicProfile + ScenarioProfile or StrategicProfile+RepresentativeProfile.

Shall we adjust it? It definitely may result in some weird error messages for users that do not have consistent profiles, so I am a bit uncertain at the moment whether we should directly include it. What are your thoughts @hellemo?

[trulsf]

I would rather leave the more complex combinations of combining profiles until we had some experience and/or usage of the new features. If there is a need they could be added at a later stage.

I have added an issue #93 to further discuss the behavior of profiles with too few values.

[JulStraus]

I agree that it is beneficial to leave it to another PR.