up previous nextpassing function parameters by referencewhere X is the identifier of a CoCoA variable. is used to pass a parameter "by reference" to afunction which may modify its value (e.g.alerts the programmer to the possibility that thevalue may be changed during the call. To write a new function which can modify some parameters use the sameto identify which formal parameters are to be passedby reference. The following example illustrates the difference betweenpassing by reference and passing by value./**/ Define CallByRef(ref L) -- "call by reference": The variable referred/**/ L := "new value"; -- to by L is changed./**/ M := "old value";/**/ CallByRef(ref M) ; -- here "ref" recalls that M might change/**/ PrintLn M;/**/ Define CallByVal(L) -- "call by value": The value of L is passed to/**/ L := "new value"; -- the function./**/ Return L;/**/ L := "old value";/**/ PrintLn L;