how to execute a function directly

Is there any way to execute a postgresql function directly?  In
Informix, there is an

EXECUTE PROCEDURE proc_name();

statement which will execute a Stored Procedure directly.

In postgresql, I can

SELECT  function_name();

or

DELETE fucntion_name();

both of which will cause the function to be executed.

I was wondering if there is a more generic way to cause a function to be
executed.

Paul Tilles