Realization:
Significantly simplify the syntax by reusing the same structure for all three “cases”.
Here are three gradually simpler syntaxes. I’m not sure what is possible to implement. They all show the following three things:
the definition
the direct call to the operator function in a filter
the call to the "operator" filter operator in a filter
Thus:
Joint parameter list everywhere, like in the pragma:
Joint parameters and soft brackets, like in the pragma:
There can be little disagreement that the latter is the simplest to learn and remember, but I can imagine this syntax is just not possible for some very good reasons.