How do I retrieve binding powers in a Maxima function definition

Thanks, that seems to be just what I need!

I don't know the distinction between mplus and "+", or if any such pairs have different binding powers. However, I want the binding power that is used in Maxima, not Lisp. The only reason I used ?+ was that I saw it in the on-line documentation for "infix" and inferred that it was the Maxima binding power.

There is other parser data that I would like to access, but can't find online documentation about how to do so.

In particular, I would like to determine if a symbol is a matchfix operator, and if so, what is its companion right delimiter?

For example, does all such information reside on the property list of a symbol?

If so, is there a function that returns the entire property list of a symbol so that I could study it and learn the proper keys to use with get()?

The reason for all of this is that I am writing a function that tries to transform an expression into a particularly narrow expression. This involves partial deparsing to compare the predicted widths. I want the program to be robust about operators added by a user, so I don't want to simply hard wire the binding powers etc. published in the on-line manual.

I would also like to automatically access character widths for the currently selected display font --the subject of an earlier mailing-list query. However, I suspect that involves forbiding forays into perhaps black-box interface, xml, and operating-system code. Until and unless I find out how to do that, the user will simply have to choose between Times New Roman and pdflatex -- or else supplement my measured width properties, which is _very_ tedious.