What is a "pure object oriented language" in the context of DCI?

Question

In DCI discussions, there is a usually mention of pure object oriented languages:

Object-oriented programming languages—particularly the "pure" ones—expressed everything in terms of objects or methods on objects. (Of course, most programming languages used classes to do this. The point is that nothing was supposed to exist outside of an object framework.)

Source: http://www.artima.com/articles/dci_vision.html

I'm trying to understand the difference between a pure OO language and a non-pure one in terms of DCI. To help put the differences into context, it would be good to have an example of a pure OO language so that I can contrast it with my experience with class based language such as java.

Question: What languages are pure OO languages (from the perspective of DCI)?

Potential 'closers': if you feel this post isn't valid for stack overflow, can you please help me understand how I can fix it rather than just marking it as a close? — Chris Snow, Dec 17 '13 at 07:09
You can fix it by deleting it. It's not a good question for [so]. See [ask]. — John Saunders, Dec 17 '13 at 07:40
This goes close to the border or opinion-based or opene-ended discussions. However, I don't think it actually crosses it, I think it's on-topic. — Lennart Regebro, Dec 17 '13 at 07:56
@LennartRegebro thanks for the info. This type of feedback is invaluable for posters. Without this type of feedback it is sometimes very difficult to know why your question is considered a bad fit. — Chris Snow, Dec 17 '13 at 08:08

score 2 · Accepted Answer · answered Dec 17 '13 at 07:52

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A non-pure OO language in this context is a language were not everything is objects. Java for example have "primitive" types, which behave differently than objects. For example, Java's primitive types are passed by value, while Java passes references when it passes it's objects.

In contrast, Python treats everything as objects, and although it has built-in types, it has no primitive types, everything is objects.

I think you misunderstand the reference to classes. I don't think they say that a pure OO language does not have classes.

answered Dec 17 '13 at 07:52

Lennart Regebro

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Is there an OO language that does not have classes? I have never encountered one. – Chris Snow Dec 17 '13 at 07:57
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@SHC Javascript, for example. – Lennart Regebro Dec 17 '13 at 08:10
I have just re-read your answer and the quote in my question and I now understand. The statement about classes was throwing me. – Chris Snow Dec 17 '13 at 08:12
Ah yes, Javascript. Thanks! – Chris Snow Dec 17 '13 at 08:17
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Another OO language without classes:Self. – Christian Horsdal Dec 17 '13 at 08:35
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Part of the point of that qoute AFAIK is that class-oriented languages, like Java, C#, C++ etc make us think in classes more than in objects. Thus more class oriented than object oriented. – Christian Horsdal Dec 17 '13 at 08:37
@ChristianHorsdal - ah, back to the essence of my question. So what is the difference in thinking in objects rather than classes? – Chris Snow Dec 17 '13 at 08:43
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Classes are write- and compile-time artifacts. Objects are what exists at runtime. Thinking more in objects than in classed brings our thinking closer how the system will run and by consequence to what the user interacts with. – Christian Horsdal Dec 17 '13 at 09:20

What is a "pure object oriented language" in the context of DCI?

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