`SignalIn`/`SignalOut` names are overloaded

[PhilipFackler]

@superwhiskers, @lukelowry, @abirchfield, @pelesh, @nkoukpaizan

TL;DR: The new SignalIn and SignalOut classes introduce some terminology confusion and should be renamed.

I failed to point this out before #570 was merged (great work on that, btw @superwhiskers).

This overloading of the terminology was part of the motivation behind the re-design. Based on multiple conversations leading to that design, my understanding was that there were three separate concepts all being referred to as "signals"...

• the actual "signal" (the value)
• the "signal node" carrying the signal
• the "port" by which a component sends or receives the signal
  ... and that we wanted to distinguish between those concepts, especially because they are all used together in the same context.

Since the terms SignalIn and SignalOut refer to the variable values that are communicated over signal nodes (and are in fact already used with that meaning in ComponentData), it doesn't make sense to use those names to refer to the "port" classes that receive/send those values.

I originally used simply InputPort and OutputPort. If the name itself needs to communicate that these are used exclusively for "signal" communication, it could be SignalInputPort and SignalOutputPort (but in that case we might also want to rename Port and PortGroup for consistency).

[nkoukpaizan]

Is the confusion that class SignalOut : public Port<scalar_type, index_type> should be, e.g., class PortOut : public Port<scalar_type, index_type>?

[PhilipFackler]

Is the confusion that class SignalOut : public Port<scalar_type, index_type> should be, e.g., class PortOut : public Port<scalar_type, index_type>?

Yes, but to be explicit:

The confusion is because the word "signal" is being used to refer to both the port type and the signal.
My suggested solution is to rename the SignalIn and SignalOut classes.
Your code in this comment is a nice option for that name change.

[pelesh]

@PhilipFackler, you are right, there is some confusion about names here, which is in part due to us changing signal implementation a couple of times. In current implementation we have three types of ports:

• electrical buses
• signal inlets
• signal outlets

There are two types of connectors:

• branches connecting electrical busses
• signal connectors connecting a signal outlet to a signal inlet (signal connectors are called signal nodes in present implementation)

We could rename SingalIn --> SignalInlet and SingalOut --> SignalOutlet to be more specific. It also may be desirable to rename SignalNode --> SignalConnector for clarity. Other than that, I don't see any name clashes in the code.

[superwhiskers]

if we all agree on renaming SignalIn to SignalInlet, SignalOut to SignalOutlet, and SignalNode to SignalConnector, we can do that. i'm not against that change.

[lukelowry]

Fine by me. On a related note I'm still in favor of making Bus a Component and exposing Vr and Vi as ports directly

[pelesh]

On a related note I'm still in favor of making Bus a Component and exposing Vr and Vi as ports directly

Please describe your proposal in a separate issue.