Re: [go-nuts] Polymorphism in GO

[LRN]

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On 11.07.2012 21:53, amiw...@gmail.com wrote:
> Hay Guys!
>
> I am looking for information about the polymorphism in GO. Can
> anyone help me find an informative topics? Explanations are great
> too!
According to [1]:

Ad-hoc polymorphism: Supported with interfaces. You call a method with
the same name on any number of objects that implement a particular
interface, and they will behave differently, depending on the
implementation.

Parametric polymorphism: No generics. But if you write a function that
works with interfaces (well, object implementing interfaces), not
types, then you can have parametric polymorphism as well (a single
function implementation that works correctly, and with the same
algorithm, on any type that implements the right interface correctly).

Subtype polymorphism: Not applicable (Go doesn't have subtyping).
Although if you embed a struct A implementing interface X into a
struct B, struct B will implement interface X, and can be used instead
of struct A in places where struct A is expected. So, kind of yes.

[1] http://en.wikipedia.org/wiki/Polymorphism_%28computer_science%29

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[Bob Hutchison]

On 2012-07-11, at 3:54 PM, LRN wrote:

> Subtype polymorphism: Not applicable (Go doesn't have subtyping).
> Although if you embed a struct A implementing interface X into a
> struct B, struct B will implement interface X, and can be used instead
> of struct A in places where struct A is expected. So, kind of yes.

I think saying "kind of" here is not doing anyone any favours. I really do not think that this behaviour would be expected from someone familiar with OO. In fact, I think they'd find it to be pretty surprising. Moreover, I'll bet many would read that paragraph you wrote and not see what you wrote, they'd see what they expected to see :-) Take a look at http://play.golang.org/p/Sji10MCx-h Many people familiar with OO (and unfamiliar with Go) will be quite surprised at the output of that program.

Cheers,
Bob

[Robert Johnstone]

Except for some built-in function, the only type of polymorphism that Go supports is interfaces.  If you want polymorphism, then that is where you need to start and finish. 

1) This trips some people up, but you will need to rely on runtime polymorphism exclusively.  Go does not have generics.  Look at the package "sort" for an idea of how this works in practice.
2) For many applications, interfaces behave similarly to virtual functions, but they are not identical.  See the example program supplied by hutch.

[Sathish VJ]

I've tried some samples in this tutorial: http://golangtutorials.blogspot.fr/2011/06/polymorphism-in-go.html.

On Wednesday, 11 July 2012 19:53:11 UTC+2, amiw...@gmail.com wrote:

Hay Guys!

I am looking for information about the polymorphism in GO.

Can anyone help me find an informative topics? 

Explanations are great too!

Thanks!

Ami

[si guy]

You can use closures to do it, I've met with limited success doing this though.
Here's an example:
http://lispy.wordpress.com/2008/09/25/roll-your-own-oo-system-with-closures-and-a-dispatch-table/