>=   <=   <>   >   <   =   +   -   *   /   %
 >=?  <=?  <>?  >?  <?  =?  +?  -?  *?  /?  %?
?>=? ?<=? ?<>? ?>? ?<? ?=? ?+? ?-? ?*? ?/? ?%?
?>=  ?<=  ?<>  ?>  ?<  ?=  ?+  ?-  ?*  ?/  ?%

**

<- ->
..
::
:> :? :?>
<< >>
<<< >>> ~~~ ^^^ &&& |||
| ||
<| <|| <|||
|> ||> |||>
~~ ~- ~+

? ^ !
!= ==
& &&

let array = [| 0 |]
let anonymousRecord = {| x = 42 |}
let range = [ for i in 0..10 -> i ]

// Custom operators

let inline (+?) (x: int) (y: int) = x + 2*y
printf "%d" (10 +? 1)

let inline (<!>) (f: 'T->'U) (x: '``Functor<'T>``) : '``Functor<'U>`` = Map.Invoke f x

let inline (<<|) (f: 'T->'U) (x: '``Functor<'T>``) : '``Functor<'U>`` = Map.Invoke f x

let inline (|>>) (x: '``Functor<'T>``) (f: 'T->'U) : '``Functor<'U>`` = Map.Invoke f x

let inline (<*>) (f: '``Applicative<'T -> 'U>``) (x: '``Applicative<'T>``) : '``Applicative<'U>`` = Apply.Invoke f x

let inline ( *>) (x: '``Applicative<'T>``) (y: '``Applicative<'U>``) : '``Applicative<'U>`` = ((fun (_: 'T) (k: 'U) -> k) <!>  x : '``Applicative<'U->'U>``) <*> y

let inline (<*  ) (x: '``Applicative<'U>``) (y: '``Applicative<'T>``): '``Applicative<'U>`` = ((fun (k: 'U) (_: 'T) -> k ) <!> x : '``Applicative<'T->'U>``) <*> y

let inline (<**>) (x: '``Applicative<'T>``) : '``Applicative<'T -> 'U>``->'``Applicative<'U>`` = flip (<*>) x

let inline (>>=) (x: '``Monad<'T>``) (f: 'T->'``Monad<'U>``) : '``Monad<'U>`` = Bind.Invoke x f

let inline (=<<) (f: 'T->'``Monad<'U>``) (x: '``Monad<'T>``) : '``Monad<'U>`` = Bind.Invoke x f

let inline (>=>) (f: 'T->'``Monad<'U>``) (g: 'U->'``Monad<'V>``) : 'T -> '``Monad<'V>`` = fun x -> Bind.Invoke (f x) g

let inline (<=<) (g: 'b->'``Monad<'V>``) (f: 'T->'``Monad<'U>``) : 'T -> '``Monad<'V>`` = fun x -> Bind.Invoke (f x) g

let inline (++) (x: 'Monoid) (y: 'Monoid) : 'Monoid = Plus.Invoke x y

let inline (<|>) (x: '``Functor<'T>``) (y: '``Functor<'T>``) : '``Functor<'T>`` = Append.Invoke x y

let inline (=>>) (s: '``Comonad<'T>``) (g: '``Comonad<'T>``->'U) : '``Comonad<'U>`` = Extend.Invoke g s

// Code quotation

open Microsoft.FSharp.Quotations
// A typed code quotation.
let expr : Expr<int> = <@ 1 + 1 @>
// An untyped code quotation.
let expr2 : Expr = <@@ 1 + 1 @@>

// Active patterns

let (|Integer|_|) (str: string) =
   let mutable intvalue = 0
   if System.Int32.TryParse(str, &intvalue) then Some(intvalue)
   else None

let (|Even|Odd|) input = if input % 2 = 0 then Even else Odd
//