topic for #10?

[Arnold deVos]

How about a little type system magic?  I think I have a small, practical example that uses a phantom type and a recursively defined type.  I would need to extract my example from our code base and clean it up and develop an explanatory story.  

Now this would not be on the level of a Miles Sabin style type system adventure.  And there would be nothing really new here. The aim would be to arm the average scala developer with another technique they may not have considered before.

Any good? 

- Arnold

[Jed Wesley-Smith]

Sounds great! Send me a title and short description and I'll post it on the meetup. Might get a little more organised this time…

[etorreborre]

+1 (I'm actually ready to +1 everyone proposing a talk given my inability to come up with one at the moment :-)).

[Arnold deVos]

Well this will not be very ambitious - but the occasional simple talk is good right?  I'll bet there will be a few who have not heard of a phantom type and some others who will find a recursive type parameter "intriguing".  I'll come back to Jed with a title soon...

[Jed Wesley-Smith]

I totally think we need a mix of approachable and challenging talks. First principles talks and general intros are awesome.

cheers,

jed.

[James Roper]

I would love to hear a presentation about the type system, I'm sure there are features that I'm not aware of that I would find very useful.

[Arnold deVos]

OK I have done some work on this.  I extracted my example material and put some effort into changing it to something generally relevant and not purely theoretical.   

[Jed Wesley-Smith]

awesome. give me a title and very short description?

[Arnold deVos]

Umm. ..

Phantom types. They have no values yet direct behavior all the same. (Sounds like a state politician.)  

A family of phantom types can represent unbounded states with no state values required. 

More than a trick, phantom types should be regarded as part of scala's machinery for ad-hoc polymorphism. 

A practical example will be offered.

[Jed Wesley-Smith]

Can you distil a one liner description perhaps? See previous episode pages for example...

cheers,

jed.

[Arnold deVos]

[repost]

How about: "Some simple type magic: a phantom type will appear before your eyes where you expected a concrete value."