4 ms·

Firstly, late binding is orthogonal to inheritance. It simply means that methods are looked up based on runtime information, rather than determined at compile t

Firstly, late binding is orthogonal to inheritance. It simply means that methods are looked up based on runtime information, rather than determined at compile time. You can have late binding in a language with no inheritance or classes at all. Secondly, OO composition does not solve the problem I described in #3. If object X has 9 methods I want to reuse in object Y, making X a component of Y still requires me to re-implement those 9 methods in Y, even if they are just pass-throughs.

couchand 7y ago
> If object X has 9 methods I want to reuse in object Y, making X a component of Y still requires me to re-implement those 9 methods in Y, even if they are just pass-throughs. That is also not universal. In Ruby, for instance, one can write: class Y def method_missing(m, *args, &block) @x.send(m, *args, &block) end end
- smrq 7y ago
  I don't think you have to squint very hard to see that as an implementation of inheritance.
  - tome 7y ago
    Will that allow the version of m in x to send messages back to y? I don't know Ruby, but most likely not.
    - kragen 7y ago
      No, for that you need to pass a self argument. See my comment below about Abadi and Cardelli's book for a (reference to a) full development of the theme.
tome 7y ago
Actually, I shouldn't have made claims about "the core reason why inheritance was developed" because I've no idea why it was developed. On the other hand, I believe I know why it is necessary (as opposed to convenient). In many languages there is functionality it provides that is otherwise unavailable. In Java, or C++, or Python, how can we allow superclass methods to call methods on a subclass (a form of late binding) without inheritance? I don't think it's possible. So unless I am much mistaken (and please correct me if I am wrong), inheritance is convenient for reducing boilerplate but necessary for late binding (in many languages). Have I made a mistake in my analysis somewhere?
- kd5bjo 7y ago
  The “superclass” can take a config object with a well-defined interface in its constructor, and call methods on this config object when it might need to do something differently.

couchand 7y ago

> If object X has 9 methods I want to reuse in object Y, making X a component of Y still requires me to re-implement those 9 methods in Y, even if they are just pass-throughs. That is also not universal. In Ruby, for instance, one can write: class Y def method_missing(m, *args, &block) @x.send(m, *args, &block) end end

smrq 7y ago
I don't think you have to squint very hard to see that as an implementation of inheritance.
- tome 7y ago
  Will that allow the version of m in x to send messages back to y? I don't know Ruby, but most likely not.
  - kragen 7y ago
    No, for that you need to pass a self argument. See my comment below about Abadi and Cardelli's book for a (reference to a) full development of the theme.

tome 7y ago

Actually, I shouldn't have made claims about "the core reason why inheritance was developed" because I've no idea why it was developed. On the other hand, I believe I know why it is necessary (as opposed to convenient). In many languages there is functionality it provides that is otherwise unavailable. In Java, or C++, or Python, how can we allow superclass methods to call methods on a subclass (a form of late binding) without inheritance? I don't think it's possible. So unless I am much mistaken (and please correct me if I am wrong), inheritance is convenient for reducing boilerplate but necessary for late binding (in many languages). Have I made a mistake in my analysis somewhere?

kd5bjo 7y ago
The “superclass” can take a config object with a well-defined interface in its constructor, and call methods on this config object when it might need to do something differently.