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Comment by harryh | Hacker News Reader

"adding an additional function to the existing collections library is something that's possible in other languages"

Is it possible in other statically compiled strongly typed languages? I don't think so?

The advantages/disadvantages of static vs. dynamic languages seem out of scope for the "is scala too complex?" question.

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See my examples below for how to do it in Gosu (via enhancements). In C# it's pretty much the same (via extension methods). Both are statically typed languages. Again, not 100% the same as Scala, and each comes with a different set of tradeoffs than the Scala approach (i.e. they're statically dispatched in Gosu), but they're certainly both reasonable, and much "simpler", solutions to the problem of "how do I add a filterMap function to all arrays or collections that works pretty much how I want it to."

Very interesting. I'm gonna go read more about this stuff now. Thanks!

You pretty much point to solutions which don't solve the problem mentioned in the blog post at all and seeing how C# extension methods basically reintroduced instanceOf checks as an implementation necessity I'm pretty sure that extension methods are the wrong way to go.

I don't remember C# extension methods being particularly prone to incur instanceOf checks, but I could be missing something; can you expand on this?

Have a look at how stuff like Count is implemented. It basically does instanceOf checks for ICollection to figure out if the underlying type supports a better way to compute the result (instead of iterating trough the whole collection).

This is completely non-extensible and people have to pay the price for this syntactic sugar (e. g. extension methods not discoverable with Reflection).

Other languages have a much cleaner approach: traits (in languages like Scala) and default methods (in Java) both solve the problem in a more straightforward and correct way.

OK I read up some on this and neither Gosu enhancement nor C# extended methods come close to what the post author is trying to attempt (adding methods to Seq and having them automatically get attached to Array, String, and CharSequence) with a single method.

So it doesn't really seem like they solve the problem "how do I add a filterMap function to all arrays or collections that works pretty much how I want it to" any simpler than Scala. All the complexity that the author brings up in his post is because he was trying to add this functionality with a single method (and a bunch of implicits).

Up top http://news.ycombinator.com/item?id=3444688 I gave working code that comes close. To be fair the reason why it gets closer (works with both F# and C# lists,arrays, sequences,dictionaries,maps,strings etc) is clerical. From this thread, I understand Scala and Java arrays are divorced.

But the problem is: put in a string and it gives back a list of characters. So I use the term it is "topologically correct" heh. To be honest I do not think there is anything functional about what he is attempting but perhaps the idioms in Scala are different? My knowledge of scala is mostly horizontal (from Ocaml,F#, haskell).

Returning the most precise result types (both collection _and_ element type) is a requirement. If this wouldn't be required, the problem would be much easier.

> Is it possible in other statically compiled strongly typed languages? I don't think so?

Sure it is :) see C# http://msdn.microsoft.com/en-us/library/bb383977.aspx

I don't see how it solves the problem mentioned.

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