A F# tail-recursive question
- by ksharp
Recently, I'm learning F#.
I try to solve problem in different ways.
Like this:
(*
[0;1;2;3;4;5;6;7;8] -> [(0,1,2);(3,4,5);(6,7,8)]
*)
//head-recursive
let rec toTriplet_v1 list=
match list with
| a::b::c::t -> (a,b,c)::(toTriplet_v1 t)
| _ -> []
//tail-recursive
let toTriplet_v2 list=
let rec loop lst acc=
match lst with
| a::b::c::t -> loop t ((a,b,c)::acc)
| _ -> acc
loop list []
//tail-recursive(???)
let toTriplet_v3 list=
let rec loop lst accfun=
match lst with
| a::b::c::t -> loop t (fun ls -> accfun ((a,b,c)::ls))
| _ -> accfun []
loop list (fun x -> x)
let funs = [toTriplet_v1; toTriplet_v2; toTriplet_v3];
funs |> List.map (fun x -> x [0..8]) |> List.iteri (fun i x -> printfn "V%d : %A" (i+1) x)
I thought the results of V2 and V3 should be the same.
But, I get the result below:
V1 : [(0, 1, 2); (3, 4, 5); (6, 7, 8)]
V2 : [(6, 7, 8); (3, 4, 5); (0, 1, 2)]
V3 : [(0, 1, 2); (3, 4, 5); (6, 7, 8)]
Why the results of V2 and V3 are different?
