9.14 Fields of packed records (Example 8.8) cannot be passed by reference in Pas- cal. Likewise, when passing a subrange variable by reference, Pascal requires that all possible values of the corresponding formal parameter be valid for the subrange: type small - 1. .100; R - record x, y : small; end; S - packed record x, y : smal1; end; var a : 1. .10; b : 1..1000; procedure foo(var n : small); begin n :- 100; writeln(a); end 9.8 Exercises 465 foo(b); foo(a); foo(c.x);(* ok *) foo(d.x);(* static semantic error *) ok) static semantic error *) Using what you have learned about parameter-passing modes, explain these language restrictions