Question

Question 2 Whether two types are structurally equivalent is ultimately a matter of inter- pretation: the language designer decides which differences between two types are significant andwhich ones are not. On page 304 of the textbook, the following algorithm for determining structuralequivalence of two types A and B is given:1 Every type T can be represented as a string sT definedinductively:

If T is a built-in type, sT is its name.

If T is a composite of a sequence of subtypes T1, ..., Tk, then sT consists of the type constructor

used to construct T followed by the strings sT1 , . . . , sTk .
For example, the string sT for the following type T is “struct char pointer int”:

struct T {
    char x;
    int *y;

};

Two types A and B are structurally equivalent if and only if sA = sB.

(a) Argue why you cannot use this definition of type equivalence to decide whether the following

two types A and B are equivalent:

struct A {
    char x;

    struct B *y;
};

struct B {
    char x;

    struct A *y;
};

Answer 1

answered by: anonymous