"Stephen Nelson-Smith" <[EMAIL PROTECTED]> wrote > "Place the following three in order: Inheritance, Polymorphism, > Encapsulation."
Interesting exercise! > Encapsulation comes with OO - you get it for free. It comes with OO but not for free. It is a fundamental property of OOP languages, but not all languages are OOP and trying to write OO programs in a non OOP language will very quickly show that encapsulation requires a lot of effort! > Polymorphism is a hugely important enabler, but this in itself > is enabled by Inheritance, Polymorphism is the root of OOP. It is what distinguishes true OOP from Modular or Object Based programming. But, it does NOT depend on inheritance, you can do polymorphism on several levels and in Python we use duck typing to create polymorphism without inheritance all the time. Inheritance is an implementation convenience, it saves writing extra code but that is all. > this order: Inheritance, Polymorphism, Encapsulation. I'd go for Encapsulation, Polymorphism, Inheritance. Without encapsulation you have no objects(*). Without polymorphism you have no OOP. Inheritance is convenient. (*) I use encapsulation in its original sense of binding data and functions together in a single unit of code - an object. Not in its frequently seen, but corrupted sense, of data hiding (using private/public data declatations etc) > My colleagues felt that of the three options this was the least > satisfactory, and showed a lack of understanding of OO design. That goes a bit far, the order is fairly argbitrary, but going by your reasoning I'd disagree with your choices as explained above. > even suggested that one could have polymorphism without inheritance. Absolutely true, see the OOP topic in my tutorial for an example in Python. Indeed some OOP languages do not support inheritance but do support polymorphism - Actor is one such. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
