On Sat, Jan 23, 2016 at 08:30:48PM +1100, Cameron Simpson wrote:
> That is the pure OO way;
Is this the room for an argument? I'd like the full half hour please.
http://www.montypython.net/scripts/argument.php
Without wishing to single out Cameron specifically, I'd like to take
exception to the way folks are tossing around the term "pure OO". I
don't think that's a term that adds much light to the discussion, and I
think it risks being understood as "real OO", a term which is downright
harmful.
At the very least, people ought to define their terms. What on earth is
"pure OO"?
If I were to guess, I would think of pure OO in one of two ways:
(1) All values in the language are objects.
That describes Python: everything in Python, modules, ints, strings,
functions, even classes themselves, are objects. That makes Python as
"pure" an object-oriented language as it is possible to get.
In comparison, Java fails miserably: unlike Python, but default Java
treats numbers, strings, booleans as native "unboxed" values, not
objects.
This is the definition of "pure OO" language given by Wikipedia:
https://en.wikipedia.org/wiki/Object-oriented_programming#OOP_languages
(2) Alternatively, "pure OO" might mean a language which uses only OO
syntax: alist.len() not len(alist).
Obviously Python is not pure in that sense, but then (i) I don't know
any language which is, most languages allow non-OO syntax at least for
arithmetic; and (ii) syntax is the most superficial and unimportant part
of Object Oriented Programming.
(3) Others (but not I) might fall for the "No True Scotsman" fallacy and
use "pure OO" to mean "proper OO", for whatever definition of "proper"
they like. Unfortunately, or perhaps fortunately, OO covers a lot of
ground, and very little is mandatory. Just as true Scotsmen do sometimes
wear trousers, and eat porridge with honey and milk, so almost any
feature of OOP is optional:
(a) Classes are optional; prototype-based languages like Javascript
and Lua are no less OO than class-based languages.
(b) Subtyping and inheritence are optional. Some people like to
reserve the term "object-based" for languages with objects but no
inheritence. Others distinguish between languages with nominal
subtyping, like C++ and Swift, and structural subtyping, like Ocaml and
Go. (Python arguably has both, as duck-typing is a form of
structural subtyping.)
I could go on, but suffice to say that I will strongly object (pun
intended) to any suggestion that Python is not a "proper" or even "pure"
OO language because it lacks certain features some other OOP languages
provide.
For example, it's popular in certain circles to say that No True OO
Language lacks information-hiding (sometimes wrongly called
encapsulation). Since Python has no "private" keyword, Python cannot be
a proper OOP language like Java, or so they say.
But Java's private variables are not that private:
http://tutorials.jenkov.com/java-reflection/private-fields-and-methods.html
and Python's cooperative information hiding ("just ignore anything
starting with a single underscore, since that's private") is actually no
less private than Java's.
--
Steve
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