What does -> mean in F#?

Question

I\'ve been trying to get into F# on and off for a while but I keep getting put off. Why?

Because no matter which \'beginners\' resource I try to look at I see very

Answer 1

First question - are you familiar with lambda expressions in C#? If so the -> in F# is the same as the => in C# (I think you read it 'goes to').

The -> operator can also be found in the context of pattern matching

match x with
| 1 -> dosomething
| _ -> dosomethingelse

I'm not sure if this is also a lambda expression, or something else, but I guess the 'goes to' still holds.

Maybe what you are really referring to is the F# parser's 'cryptic' responses:

> let add a b = a + b
val add: int -> int -> int

This means (as most of the examples explain) that add is a 'val' that takes two ints and returns an int. To me this was totally opaque to start with. I mean, how do I know that add isn't a val that takes one int and returns two ints?

Well, the thing is that in a sense, it does. If I give add just one int, I get back an (int -> int):

> let inc = add 1
val inc: int -> int

This (currying) is one of the things that makes F# so sexy, for me.

For helpful info on F#, I have found that blogs are FAR more useful that any of the official 'documentation': Here are some names to check out

• Dustin Campbell (that's diditwith.net, cited in another answer)
• Don Symes ('the' man)
• Tomasp.net (aka Tomas Petricek)
• Andrew Kennedy (for units of measure)
• Fsharp.it (famous for the Project Euler solutions)
• http://lorgonblog.spaces.live.com/Blog (aka Brian)
• Jomo Fisher