I do both C# and F#. But, at this point I think in ML no matter what which language I'm using. That said, though I'm delighted by F#, there are things that I re

I do both C# and F#. But, at this point I think in ML no matter what which language I'm using. That said, though I'm delighted by F#, there are things that I really miss about C#: * Haskell's type classes are awesome, and neither F# nor C# have them. But, you can realize them with a really simple pattern in C# whereas in F# you have to resort to reflection or generic hacks[1] (but inline functions usually make such hacks nicer in F#). * Sum types are awesome. F# realizes them in two ways: with discriminated unions and pattern matching (mainly), or with abstract classes and inheritance. Both are powerful approaches, but the latter is particularly useful when you need unbounded sum types. Unfortunately, inheritance is somewhat crippled in F# because you can't define protected members (though you can override them). I find myself needing this when I'm designing a solution rather than merely implementing one. For instance, I find that designing a language/compiler is much easier with C# than with idiomatic F#. * This is kind of a summary of the first two points: idiomatic C# is a better dynamic language, and I'm not referring to the `dynamic` keyword, though it certainly helps. I've created some really nice and secure APIs by making use of user-defined conversions. System.Linq.Xml is a good example of what I'm talking about. * Finally, idiomatic C# is a nicer classical OO language than idiomatic F#. This is kind of obvious since F# is a "functional language" with OO features whereas C# is an OO language with functional features. But, when I say classical OO, I mean the Smalltalk style OO that came before C++. Alan Kay defined that kind of OOP as (1) Encapsulation, (2) Message Passing, and (3) extreme late binding. Neither C# nor F# quite has (2) and (3), but C# gets me the closest without coloring too far outside of the lines. Of course, this begs the question that OO is better than functional. Having done both for a long time, I'm convinced that it is the case (though I do think learning functional programming is the fastest path to getting good at OO). Lamentably, I can't yet defend this point too vigorously because I've only just discovered the joy or Smalltalk. But, here is a preview of sorts: Imagine being able to update a database schema and having your statically-typed code continue to run without needing to recompile. [1] http://stackoverflow.com/questions/9868327/f-type-constraints-and-overloading-resolution http://stackoverflow.com/questions/9868327/f-type-constraint...