fbp: allow to omit ports if only one exists

[barbieri]

While manually writing FBP it is inconvenient to type the port name if the node provides a single port, namely this:

_(gpio/reader) OUT -> IN _(console)

could be expressed more concisely as:

_(gpio/reader) -> _(console)

[otaviobp]

+1 for this issue too. But I have some comments about it:

• Nodes have error output ports, so we should be implicit for nodes that a single port, except error ports.
• If another port is added to the node, we break the node API. And that is not happening with current version of fbp.

I suggest to make OUT and IN ports implicit. So independently of the number of ports a node have, we use IN/OUT ports if no port is explicitly selected.

[ibriano]

On Tue, 08 Mar 2016 05:09:59 -0800, Otávio wrote:

+1 for this issue too. But I have some comments about it:

• Nodes have error output ports, so we should be implicit for nodes that a single port, except error ports.
• If another port is added to the node, we break the node API. And that is not happening with current version of fbp.

I suggest to make OUT and IN ports implicit. So independently of the number of ports a node have, we use IN/OUT ports if no port is explicitly selected.

And what to they map to? And what type do they have?

[barbieri]

he means if out output port is specified, you assumed "OUT", if there is a port with such name. It's an "alias".

[bdilly]

I don't like that too much, actually

Imo explicit is better than implicit. Also you're creating one extra way to write the same thing. I don't think it makes it much easier to read.

Port names should be descriptive and help users to understand what should be feed to nodes and what should be the outcomes.

[glima]

-1 for this as well.