[PD] Abstraction arguments: tell apart symbols from floats from no argument at all

[Peter P.]

Hi list,

please excuse me if this has been discussed numerous times, but the
search engine at https://lists.puredata.info/pipermail/pd-list/ does not
give me reasonable answers.

I am writing an abstraction and for one of its numeric arguments I would
like to detect if it has been not specified, or if it has been set to a
float including 0. How can I do this?

I would also like to detect if another argument is a float or a symbol and
process these two differently without causing Pd error messages. Is this
possible?

Thank you!
P