Inheritance structure less important in dynamic languages?

[Marvin]

Hi,

It's been claimed that inheritance structures are less important in dynamic
languages like Python. Why is that and where can i read more about that?

/Marv

[Ben Finney]

"Marvin" <ma**@mailcity.com> writes:

It's been claimed that inheritance structures are less important in
dynamic languages like Python.
Who claimed that? I ask not because I doubt your assertion ("it was
claimed"), but rather that if someone claimed something, it seems
better to ask that person your next question:
Why is that and where can i read more about that?

The person who claimed it is more likely to be able and willing to
defend it.

--
\ Eccles: "I just saw the Earth through the clouds!" Lew: "Did |
`\ it look round?" Eccles: "Yes, but I don't think it saw me." |
_o__) -- The Goon Show, _Wings Over Dagenham_ |
Ben Finney

[bruno at modulix]

Marvin wrote:

Hi,

It's been claimed
s/claimed/observed/

In Python and Ruby, class hierarchies tends to be *really* flat when
compared to Java or C++.
that inheritance structures are less important in dynamic
languages like Python. Why is that
Don't you guess ?-)

A very obvious point is that in a dynamically typed language,
inheritence is only about implementation - it's not used for class-based
polymorphism (subtyping).

Also, dynamic languages are usually very strong on introspection and
offer good support for automatic delegation ("DoesNotUnderstand" in
Smalltalk, __getattr__ in Python, etc), which tend to lower the use of
inheritence for "private inheritence" (ie: implementation reuse without
any subtyping semantic).

This leaves with only three real use-case for inheritence :
* factoring common features of a set of related classes in an abstract
base class
* specialisation of an existing class (proper subclassing),
* mixins.
and where can i read more about that?

"duck typing", "implied interface" and "composition/delegation" could be
good starting points for a google search.

--
bruno desthuilliers
python -c "print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in 'o****@xiludom.gro'.split('@')])"