Query the kind of calling a funcion

Dear all,


My question is concerned to the kind how a function is called.

Example A:

 > foo(1)

Example B:

 > a <- foo(1)


Is there any way for the function foo() to recognise whether the  
returned value of foo() is stored in a variable or not, i.e. to  
distinguish between Example A and B?


Any comments are welcomed.

Many thanks in advance

Hans