Object Oriented Programming
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Excellent explanation of the differences between [[OOP]] approach and the ''functional'' one can be summarized into: | Excellent explanation of the differences between [[OOP]] approach and the ''functional'' one can be summarized into: | ||
* In classical [[OOP]] one only knows own identity. Identity (and implementation) of others can be inspected only calling their methods (sending them messages) | * In classical [[OOP]] one only knows own identity. Identity (and implementation) of others can be inspected only calling their methods (sending them messages) | ||
| - | * In functional world (when using algebraic types) the person that defines a type can | + | * In functional world (when using algebraic types) the person that defines a type can inspect internals of all instances of the same type |
Last but not least the [http://www.cs.utexas.edu/~wcook/Drafts/2009/essay.pdf essay] mentions the [[expression problem]] which I also analysed in [[TheAPIBook]]'s chapter 18: [[Chapter 18|Extensible Visitor Pattern Case Study]]. | Last but not least the [http://www.cs.utexas.edu/~wcook/Drafts/2009/essay.pdf essay] mentions the [[expression problem]] which I also analysed in [[TheAPIBook]]'s chapter 18: [[Chapter 18|Extensible Visitor Pattern Case Study]]. | ||
Revision as of 08:22, 3 November 2009
This is my personal take on OOP. In case you are searching for objective view, then rather see official wikipedia's explanation.
Revolutionary view
Let me point you to an essay explaining OOP in completely revolutionary view. I especially like statements like:
- Typical object oriented program relies on functions more than many functional programs.
- λ-calculus was the first OOP language
Excellent explanation of the differences between OOP approach and the functional one can be summarized into:
- In classical OOP one only knows own identity. Identity (and implementation) of others can be inspected only calling their methods (sending them messages)
- In functional world (when using algebraic types) the person that defines a type can inspect internals of all instances of the same type
Last but not least the essay mentions the expression problem which I also analysed in TheAPIBook's chapter 18: Extensible Visitor Pattern Case Study.
History
OOP is no longer what it used to be. Somehow the original great visions diluted and instead we have class/object/inheritance as present in Java and other OOP languages of these days. The daily experience we have with these languages is so strong, so defining that we sometimes tend to forget that the roots of OOP used to be driven by visions and not technical concepts.
I was reminded about that recently when I read Motivation for DCI at artima website. Just few quotes:
- Object oriented programming grew out as vision of the computer
- as an extension of the human mind.
Wow! Really? Makes sense, but this is a piece of wisdom lost for a long time, am I right? Even when I learned about OOP I heard more the explanation describing the methodology as inspired by nature. The inheritance was the most natural way to define base class Mammal and subclasses Cat and Dog.
Our brain can definitely capture more complex concepts than the mammal example, so maybe, if we want to stick with the old definition, the meaning of OOP shall be expanded. Definitely beyond the expressive capabilities of C++ and Java.
- MVC's goal was to provide the illusion of a direct connection
- from the end user brain to the computer "brain"
- a large method that represented an entire algorithm was believed to
- not be a "pure" object-oriented design
- This use of inheritance crept out of the world of programming
- language into the vernacular of design
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