https://en.wikipedia.org/wiki/Composition_over_inheritance
http://programmers.stackexchange.com/questions/134097/why-should-i-prefer-composition-over-inheritance https://www.thoughtworks.com/insights/blog/composition-vs-inheritance-how-choose That's just the start. Overtime, people realized inheritance can be quite fragile, so many style guidelines simply forbid you from doing it. On Monday, September 12, 2016 at 11:45:40 AM UTC-7, Bart Janssens wrote: > > Looking at this example, it seems mighty tempting to have the ability to > subtype a concrete type. Are the exact problems with that documented > somewhere? I am aware of the following section in the docs: > > "One particularly distinctive feature of Julia’s type system is that > concrete types may not subtype each other: all concrete types are final and > may only have abstract types as their supertypes. While this might at first > seem unduly restrictive, it has many beneficial consequences with > surprisingly few drawbacks. It turns out that being able to inherit > behavior is much more important than being able to inherit structure, and > inheriting both causes significant difficulties in traditional > object-oriented languages." > > I'm just wondering what the "significant difficulties" are, not advocating > changing this behaviour. > > On Mon, Sep 12, 2016 at 5:28 PM Stefan Karpinski <ste...@karpinski.org > <javascript:>> wrote: > >> I would probably go with approach #2 myself and only refer to the .bar >> and .baz fields in all of the generic AbstractFoo methods. >> >> On Mon, Sep 12, 2016 at 10:10 AM, Michael Borregaard <mkborr...@gmail.com >> <javascript:>> wrote: >> >>> Hi, >>> >>> I am defining a set of types to hold scientific data, and trying to get >>> the best out of Julia's type system. The types in my example are 'nested' >>> in the sense that each type will hold progressively more information and >>> thus allow the user to do progressively more. Like this: >>> >>> type Foo >>> bar >>> baz >>> end >>> >>> type Foobar >>> bar # this >>> baz # and this are identical with Foo >>> barbaz >>> bazbaz >>> end >>> >>> >>
