> restart;\

> a:=(x,y)->x^2+y^2;a(x,y);

                                             2    2
                              a := (x,y) -> x  + y

                                      2    2
                                     x  + y
--------------------------------------------------------------------------------
> x:=1;y:=2;\
b:=(x,y)->x^2+y^2;b(x,y);

                                     x := 1

                                     y := 2

                                             2    2
                              b := (x,y) -> x  + y

                                        5
--------------------------------------------------------------------------------
> readlib(unassign):\
unassign(x,y);\
c:=(x,y)->x^2+y^2;c(x,y);
Error, (in assign) invalid arguments


                                             2    2
                              c := (x,y) -> x  + y

                                        5
--------------------------------------------------------------------------------
> unassign('x','y');\
d:=(x,y)->x^2+y^2;d(x,y);\


                                             2    2
                              d := (x,y) -> x  + y

                                      2    2
                                     x  + y
--------------------------------------------------------------------------------
>