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Lab1

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(* fibonacci numbers in O(n) with tail recursion *)
let fib n =
    let rec fib' a b i =
        if i=n then a+b
        else fib' b (a+b) (i+1)
    if n<=0 then 0
    elif n=1 || n=2 then 1
    else fib' 1 1 3

map with fold *

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let map' f lst = List.fold (fun acc x -> (f x)::acc) [] lst 
                 |> List.rev

map' (fun x -> x*2) [1;2;3;4;5]

convert a number to the decimal number system *

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let convert x radix = 
    List.foldBack2 (fun dig pow acc ->
                        acc + dig * (pown radix pow))
                   x
                   (List.rev [0..x.Length-1])
                   0

let convert' x radix = 
    List.mapi (fun i x -> x * (pown radix i)) (List.rev x)
    |> List.sum


let convert'' x radix = (* without library list functions *)
    match x with
    | [] -> 0
    | h::t  -> h * (pown radix (x.Length-1)) + 
                (convert t radix)

convert [1;1;1] 2 
(* 7 *)
convert [1;15] 16 
(* 31 *)

val fib : n:int -> int

Full name: Script.fib

val n : int

val fib' : (int -> int -> int -> int)

val a : int

val b : int

val i : int

val map' : f:('a -> 'b) -> lst:'a list -> 'b list

Full name: Script.map'

val f : ('a -> 'b)

val lst : 'a list

Multiple items
module List

from Microsoft.FSharp.Collections

--------------------
type List<'T> =
  | ( [] )
  | ( :: ) of Head: 'T * Tail: 'T list
  interface IEnumerable
  interface IEnumerable<'T>
  member Head : 'T
  member IsEmpty : bool
  member Item : index:int -> 'T with get
  member Length : int
  member Tail : 'T list
  static member Cons : head:'T * tail:'T list -> 'T list
  static member Empty : 'T list

Full name: Microsoft.FSharp.Collections.List<_>

val fold : folder:('State -> 'T -> 'State) -> state:'State -> list:'T list -> 'State

Full name: Microsoft.FSharp.Collections.List.fold

val acc : 'b list

val x : 'a

val rev : list:'T list -> 'T list

Full name: Microsoft.FSharp.Collections.List.rev

val x : int

val convert : x:int list -> radix:int -> int

Full name: Script.convert

val x : int list

val radix : int

val foldBack2 : folder:('T1 -> 'T2 -> 'State -> 'State) -> list1:'T1 list -> list2:'T2 list -> state:'State -> 'State

Full name: Microsoft.FSharp.Collections.List.foldBack2

val dig : int

val pow : int

val acc : int

val pown : x:'T -> n:int -> 'T (requires member get_One and member ( * ) and member ( / ))

Full name: Microsoft.FSharp.Core.Operators.pown

property List.Length: int

val convert' : x:int list -> radix:int -> int

Full name: Script.convert'

val mapi : mapping:(int -> 'T -> 'U) -> list:'T list -> 'U list

Full name: Microsoft.FSharp.Collections.List.mapi

val sum : list:'T list -> 'T (requires member ( + ) and member get_Zero)

Full name: Microsoft.FSharp.Collections.List.sum

val convert'' : x:int list -> radix:int -> int

Full name: Script.convert''

val h : int

val t : int list

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Link:	http://fssnip.net/af
Posted:	14 years ago
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