Although statement functions have a limited role to play in programs because they can only be defined in a single statement, references to statement functions they may be executed more efficiently than references to external functions; many modern compilers expand statement function references to in-line code when it is advantageous to do so.
If the same statement function is needed in more than one program unit it would is possible to use an INCLUDE facility to provide the same definition each time, but it will usually be better to use an external function instead.