It is kind of funny that F# 4.0 got to the top of Hacker news while F# 3.0 with the type providers (which is an amazing innovation, if you ask me) didn't get that much publicity when it came out.
I think it's just a matter of timing. Now that the F# community is getting bigger (see number of user groups at http://c4fsharp.net), more stable (see the F# Foundation http://foundation.fsharp.org), and Microsoft is becoming more open (reinforcing the already much more open F# space), it is just a good time for looking into F#. And F# 4.0 announcement is a good excuse for that :-).
Though F# 4.0 is the first version of the language designed and developed in a fully open way, which is pretty amazing change - and more important than many language features that could be added to F#.
F# 4.0 makes me excited to be using the language even more. I just started learning back in December after not really enjoying my Python learning experience and have found F# to be such a joy. Your book is one of three at my desk. I've done about 8 years on the .NET stack and Microsoft as a whole has really impressed me these past couple years.
Anyway, thanks for all the work you have put into making the F# community one that is thriving and active! I see your name everywhere when I'm Googling for F# stuff and it's obvious you are one of those 20-percenters doing 80-percent of the work!
"The .NET framework supports up to 32-dimensional arrays, but in the past F# only supported use of up to rank-4 arrays. Not only were arrays of rank 5+ not possible to create and manipulate from F# code, the compiler could sometimes fail to consume external libraries which relied on high-dimensional arrays.
This is now fixed. Although there is not yet support for creating and manipulating high-rank arrays, the compiler will now properly handle these types up to rank-32."
Has anyone here ever used "high-rank" arrays? The deepest I've ever gone was 4 for a lookup table, but I'm wondering what the use-case is for super high depth arrays as well as why there is a limit at all.
I contributed the fix for the high-ranking array support.
The main reason for the fix was because F# pre-4.0 can't reference overloaded methods where one or more of the overloads has one or more parameters which is an array of rank 5 or more. I had a 3rd party DLL I wanted to reference, where a class had generic overloads for all of the array ranks, e.g.,:
Even though I was only trying to use MyClass.Foo(T[]), the F# compiler's overload resolution failed due to the presence of the higher-ranked array types.
I'm not planning to use such arrays any time soon, but I wanted to make sure that if other code was using these arrays I could reference it from F#.
Unfortunately F# doesn't really have macro support... "working with expression trees is becoming easier than ever" but you can't actually unquote/eval an arbitrary expression tree.
The only purpose I can see for expression trees is implementing a DSL with F# syntax.
