Any Gamma expression which makes a call to a function, such as tan(3.14159), causes a change of program flow, entering a new scope and causing execution to be temporarily diverted into the function being called. In most cases, the function simply returns and flow continues at the expression containing the function call.

If an error occurs during a function call, the function will not return, and execution will continue from the most recent protect/unwind or try/catch construct (see the Error Handling section of this chapter).