For quite a time I was looking for a different programming language I could try, because working constantly with C++ can be strenuous. My initial plan was Ruby or even Python, but I found out that just installing them on unix system (OSX) was more than I could handle. I had also planned to update from Visual Studio 2010 to 2015 and noticed that VS2015 is pre-installed with F#. So it was easy to start hacking with it. (Note: you can keep 2010 along with 2015 which is nice, because all my projects are on 2010.)
F# is mainly a functional language and it has been nice to approach programming from another perspective. In functional paradigm you are supposed to input parameters to a function and get some kind of result. It could be thought as a procedure becoming an algorithm itself, rather than containing it. At least that's the way I'm understanding it.
In real life programs pure functional style is difficult to use, because you are not supposed to have variables, but only constants computed from other constants. Yes, it does sound crazy. For convenient reasons F# does have variables that can be created using mutable keyword. F# has also classes which is another good option to have.
The learning barrier to F# is surprisingly low, at least when you get started with the language. Sometimes the syntax is bit confusing (for someone with mainly C++ background), but it's possible to get it right when trying hard. Couple of things I noticed were tuples (which are used in Console-routines). When you use (x, y) notation it's a tuple, not two parameters as in C++. Also, for some reason you have to create a tuple using let a = (x, y) and pass 'a' to Console-functions for them to work, for whatever reason.
Another subtle thing is unit as a C-style void return value. The proper way to write void function returning void is let function() : unit = //some code and also remember to call it like this: function() with parentheses. Or even more strictly using do-keyword: do function().
The way F# source files are arranged is also a bit crazy. They are in a list where top most files are used by files lower in the list. You can't call a function unless it's declared above. I guess it's actually possible to write large programs using this style, but it seems to be quite primitive. All source files are always compiled for this reason which makes compile times slow even on small projects.
I'm not really that excited about functional programming. I guess it solves some problems as it forces the use of constants. It's like having C++ const as default and mutable only when you need variables. This is something you kind of start to use in C++ as well when you become a better programmer. I've noticed that most of my variables are const type and you start to become more const correct with experience. Even so, the way F# has mutable variables and classes shows that they are useful to have, rather than trying to follow a strict functional path.
The obvious thing to do with F# is of course to create a roguelike and that's what I have already started to program. It feels like I have to proceed with caution to find more functional ways to implement stuff and I'm sure it's a good way to learn something new.