Pointer subtraction in C +

[anonymous_user_9dbe0c46]

int operator -(Stringp &s1, Stringp &s2)
{
struct Exception *exc = GetAnExceptionStructure();
PRECONDITION((Strvalidp(s1) && Strvalidp(s2) &&
s1.parent == s2.parent), exc);
return s1.content - s2.content;
}

The operator verifies that both pointers are valid, and that they point to the same string. The operation is more restricted than in traditional C since a subtraction operation is considered
invalid if the pointers do not point to the same parent