I know that this is very old thread but I also reached here yesterday so I think this might be useful to someone like me!
I am using MobMuPlat(=MMP) + Pd and MMP can get user string input and Pd also can receive it.
If I type sth. like -34.123456 then Pd also can get it but in string not as a number!
To convert this back to a proper floating point number, I have managed to implement a working object for my situation.
Hope this help someone else in the future.
It is using [list symbol] to get series of numbers first, and detect characters one by one to do needed actions with several variables ([expr]), and then finally spits out integral part & fractional part.
BTW, this is my first post to the Pd community.
I really love Pure Data.
Thank you for making it & supporting it !