How do you determine the namespace of a function?

Question

Given a function, how do you determine which namespace it has come from?

For example, if I type mean.default at the command prompt, the output includes

Answer 1

I very recently learned about find() which seems to do just this.

R> find("ls")
[1] "package:base"
R> find("na.locf")
[1] "package:zoo"