fsharp-goodies-v1.md

Fsharp goodies (Vol 1)

After the 'F# Compiler Community Session' I read the first 1K lines of SyntaxTree.fs. That's what I learned about the language.

1. There is a byte string

   let a = "abc"B
   val a : byte [] = [|97uy; 98uy; 99uy|]

2. You can specify the expected type behind any expression

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

3. Discriminated Union augmentations can be disabled

   [<DefaultAugmentation(false)>]
   type Animal =
       | Snake
       | Dog
       | Cat
   
   	(* fails when default augmentations are enabled (default) *)
       member this.IsDog =
           match this with
           | Dog -> true
           | _ -> false

4. There is a strange but supported property setting syntax (but please don't use it)

   let arr = ResizeArray([|1; 2; 3|])
   arr.Item(0) <- 42

Yes please don't use 3 or 4

3 has bugs in conjunction with other features

4 is actually a dotnet and vb thing