CSCI 3155, Quiz 5
20 minutes

Throughout this quiz assume Modula-3 type rules.

Consider the following types:

TYPE T = OBJECT x: INTEGER; END:
     U = T OBJECT c: CHAR; END;
     V <: U;
     W = OBJECT x: INTEGER; c: CHAR; END;

VAR t: T; u: U; v: V; w: W; r: REFANY;

Assume that all variables are already initialized with appropriate objects
and that elsewhere in the program there is a full revelation of V.

Indicate which of these statements are legal in Modula-3 and why.  Also
indicate if any of these statements need a run-time check.

(i) (2 points) t := u;
(ii) (2 points) t := v;
(iii) (2 points) t := w;
(iv) (2 points) v := t;
(v) (2 points) t := r;