How to link personnal c++ functions in ROOT subroutine

I wrote some functions for ROOT for generic purpose (sorting, peak finding, etc) and I wish to call them in other subroutines. Until now, I just copied my functions in these subroutines.
So, I would like to know if it is possible to put all these functions in a same file and to make an external call when I need.
Briefly, I would like to write something like


put the declarations into a header file (e.g. myfunctions.h) and the definitions into a source file (e.g. myfunctions.cxx), and load the source file into ROOT with .L myfunctions.cxx+. Now all your subroutines can call any function in myfunctions.h.

Cheers, Axel.