Playing with ranges

range.fsx

let (..) (start:int) (limit:int) =
    let sequence = [start..limit]

    let decapitate h t =
        if t = List.empty 
        then [ h ]
        else t |> List.rev

    let reversed =
        match sequence with
        | h::t -> decapitate h t
        | [] ->  List.empty
    
    if (reversed |> List.length > 1)
    then
        match reversed with
        | h::t -> List.toSeq (decapitate h t)
        | [] ->  Seq.empty
    else Seq.empty

let logAndAssert actual expected =
    printfn "expect %A to be %A: result %A: (expected=%A:actual=%A)" actual expected (expected=actual) expected actual

let t1 = [0..-1]
let t2 = [0..0]
let t3 = [0..1]
let t4 = [0..2]
let t5 = [5..9]
let t6 = [-3..2]

logAndAssert t1 []
logAndAssert t2 []
logAndAssert t3 []
logAndAssert t4 [1]
logAndAssert t5 [6;7;8]

logAndAssert t6 [-2;-1;0;1]