I'm having a little difficultly with inheritance.
I want to have a class "SubT" inherit from class "T".
SubT contains all the information in T, plus a little more based upon
the member variables of T.
For efficiency, I cannot merely have a T object in SubT.
What I'd like is something as follows:
class T {
T(int a) : _a(a) {}
protected:
int _a;
};
class SubT : public T {
SubT(int a) : _a(a), _b(a+a) {}
SubT(T foo) : _a(foo._a), _b(foo._a+foo._a) {}
public:
int _b;
};
Unfortunately, SubT doesn't seem to contain member variable _a. Why
not?
Could someone suggest an efficient way to write the constructors for
SubT?
[Assume that SubT needs to contain both _a, and _b, and that you can't
optimize one out.]
Joseph
1  1742 
Joseph Turian wrote: I'm having a little difficultly with inheritance.
I want to have a class "SubT" inherit from class "T".
SubT contains all the information in T, plus a little more based upon
the member variables of T.
For efficiency, I cannot merely have a T object in SubT.
What I'd like is something as follows:
class T {
T(int a) : _a(a) {}
protected:
int _a;
};
class SubT : public T {
SubT(int a) : _a(a), _b(a+a) {}
SubT(T foo) : _a(foo._a), _b(foo._a+foo._a) {}
public:
int _b;
};
Unfortunately, SubT doesn't seem to contain member variable _a. Why
not?
It does, but not directly, it contains T, which contains a.
Could someone suggest an efficient way to write the constructors for
SubT?
You should use the T cosntructor, like this
SubT(int a) : T(a), _b(a+a) {}
SubT(T foo) : T(foo._a), _b(foo._a+foo._a) {}
[Assume that SubT needs to contain both _a, and _b, and that you can't
optimize one out.]
Joseph
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