Yes, I saw the "uses" clause in your code, which I didn't know, and even though I didn't use it in my preceding function, I will certainly in the future.
I also learned about typing parameters (I knew this, but I understand that typing is much more flexible than I thought). As well as a few tricks for functional programming, with @and ~ (I knew them, more or less).
There is one thing, though, that I have already seen in Maple library source, and I didn't see it yet in the documentation: what do those ':-' mean in quoted symbols, such as ':-symmetric'? I know the syntax package:-function, but what about this usage?
Edit: I found it in the manual (it's simply '?:-'): The ":-" operator can also be used as a unary, prefix operator, whose sole operand is a symbol. The expression :-sym evaluates to the global instance of "sym", even if there is a local binding for "sym" in scope.
Thanks for your help.