HList with Mapper and Folder

Extended from: http://www.fssnip.net/d2

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type HList = interface end
and HNil = HNil with
    static member inline (|*|) (f, HNil) = f $ HNil
    static member inline Map (m, HNil) = HNil
    interface HList
and HCons<'a, 'b when 'b :> HList> = HCons of 'a * 'b with
    static member inline (|*|) (f, HCons(x, xs)) = f $ HCons(x, xs) 
    interface HList 

let inline head (HCons(h,t)) = h
let inline tail (HCons(h,t)) = t

type Peano = interface end
and Zero = Zero with
    static member inline (|*|) (f, Zero) = f $ Zero
    interface Peano
and Succ<'a when 'a :> Peano> = Succ of 'a  with
    static member inline (|*|) (f, Succ(x)) = f $ Succ(x) 
    interface Peano 

type Bool = interface end
and True = True with
    interface Bool
and False = False with
    interface Bool

let inline (^+^) head tail = HCons(head, tail)

// Examples

type Append = Append with
    static member ($) (Append, HNil) = id
    static member inline ($) (Append, HCons(x, xs)) = fun list ->
        HCons (x, (Append |*| xs) list)

type TMapper = TMapper with
    static member inline Map (s: string) = ""
    static member inline Map (i: int) = 0

type ZeroMapper = ZeroMapper with
    static member ($) (ZeroMapper, HNil) = HNil
    static member inline ($) (ZeroMapper, HCons(x : string, xs)) = HCons("", ZeroMapper |*| xs)
    static member inline ($) (ZeroMapper, HCons(x : int, xs)) = HCons(0, ZeroMapper |*| xs)

type Length = Length with
    static member ($) (Length, HNil) = Zero
    static member inline ($) (Length, HCons(x, xs)) = Succ (Length |*| xs) 


let first = 1 ^+^ '1' ^+^ HNil
let second =  "1" ^+^ true ^+^ HNil
let third = "one" ^+^ 123 ^+^ HNil

ZeroMapper $ third // HCons<string,HCons<int,HNil>> = HCons ("",HCons (0,HNil))
ZeroMapper $ second // type error, no char version of ZeroMapper defined

// result : HCons<int,HCons<char,HCons<string,HCons<bool,HNil>>>>
let result = (Append $ first) second // HCons (1,HCons ('1',HCons ("1",HCons (true,HNil))))

tail third // HCons (123,HNil)
(tail >> tail) third // HNil
(tail >> tail >> tail) third // compiler error

// length : Succ<Succ<Succ<Succ<Zero>>>>
let length = Length $ result // Succ (Succ (Succ (Succ Zero)))

Multiple items
union case HNil.HNil: HNil

--------------------
type HNil =
  | HNil
  interface HList
  static member Map : m:'a * HNil:HNil -> HNil
  static member ( |*| ) : f:'a * HNil:HNil -> '_arg6 (requires member ( $ ))

Full name: Script.HNil

val f : 'a (requires member ( $ ))

Multiple items
static member HNil.Map : m:'a * HNil:HNil -> HNil

Full name: Script.HNil.Map

--------------------
module Map

from Microsoft.FSharp.Collections

--------------------
type Map<'Key,'Value (requires comparison)> =
  interface IEnumerable
  interface IComparable
  interface IEnumerable<KeyValuePair<'Key,'Value>>
  interface ICollection<KeyValuePair<'Key,'Value>>
  interface IDictionary<'Key,'Value>
  new : elements:seq<'Key * 'Value> -> Map<'Key,'Value>
  member Add : key:'Key * value:'Value -> Map<'Key,'Value>
  member ContainsKey : key:'Key -> bool
  override Equals : obj -> bool
  member Remove : key:'Key -> Map<'Key,'Value>
  ...

Full name: Microsoft.FSharp.Collections.Map<_,_>

--------------------
new : elements:seq<'Key * 'Value> -> Map<'Key,'Value>

val m : 'a

type HList

Full name: Script.HList

Multiple items
union case HCons.HCons: 'a * 'b -> HCons<'a,'b>

--------------------
type HCons<'a,'b (requires 'b :> HList)> =
  | HCons of 'a * 'b
  interface HList
  static member ( |*| ) : f:'a0 * HCons<'b1,'c> -> '_arg9 (requires member ( $ ) and 'c :> HList)

Full name: Script.HCons<_,_>

val f : 'a (requires member ( $ ) and 'c :> HList)

val x : 'b

val xs : #HList

val head : HCons<'a,#HList> -> 'a

Full name: Script.head

val h : 'a

val t : #HList

val tail : HCons<'a,'b> -> 'b (requires 'b :> HList)

Full name: Script.tail

type Peano

Full name: Script.Peano

Multiple items
union case Zero.Zero: Zero

--------------------
type Zero =
  | Zero
  interface Peano
  static member ( |*| ) : f:'a * Zero:Zero -> '_arg5 (requires member ( $ ))

Full name: Script.Zero

Multiple items
union case Succ.Succ: 'a -> Succ<'a>

--------------------
type Succ<'a (requires 'a :> Peano)> =
  | Succ of 'a
  interface Peano
  static member ( |*| ) : f:'a0 * Succ<'b> -> '_arg8 (requires member ( $ ) and 'b :> Peano)

Full name: Script.Succ<_>

val f : 'a (requires member ( $ ) and 'b :> Peano)

val x : #Peano

type Bool

Full name: Script.Bool

Multiple items
union case True.True: True

--------------------
type True =
| True
interface Bool

Full name: Script.True

type False =
| False
interface Bool

Full name: Script.False

Multiple items
union case False.False: False

--------------------
type False =
| False
interface Bool

Full name: Script.False

val head : 'a

val tail : #HList

Multiple items
union case Append.Append: Append

--------------------
type Append =
  | Append
  static member ( $ ) : Append:Append * HNil:HNil -> ('a -> 'a)
  static member ( $ ) : Append:Append * HCons<'a,'b> -> ('c -> HCons<'a,'d>) (requires 'b :> HList and member ( |*| ) and 'd :> HList)

Full name: Script.Append

val id : x:'T -> 'T

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

val x : 'a

val xs : 'b (requires 'b :> HList and member ( |*| ) and 'd :> HList)

Multiple items
val list : 'c

--------------------
type 'T list = List<'T>

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

Multiple items
union case TMapper.TMapper: TMapper

--------------------
type TMapper =
  | TMapper
  static member Map : s:string -> string
  static member Map : i:int -> int

Full name: Script.TMapper

Multiple items
static member TMapper.Map : s:string -> string

Full name: Script.TMapper.Map

--------------------
module Map

from Microsoft.FSharp.Collections

--------------------
type Map<'Key,'Value (requires comparison)> =
  interface IEnumerable
  interface IComparable
  interface IEnumerable<KeyValuePair<'Key,'Value>>
  interface ICollection<KeyValuePair<'Key,'Value>>
  interface IDictionary<'Key,'Value>
  new : elements:seq<'Key * 'Value> -> Map<'Key,'Value>
  member Add : key:'Key * value:'Value -> Map<'Key,'Value>
  member ContainsKey : key:'Key -> bool
  override Equals : obj -> bool
  member Remove : key:'Key -> Map<'Key,'Value>
  ...

Full name: Microsoft.FSharp.Collections.Map<_,_>

--------------------
new : elements:seq<'Key * 'Value> -> Map<'Key,'Value>

val s : string

Multiple items
val string : value:'T -> string

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

--------------------
type string = System.String

Full name: Microsoft.FSharp.Core.string

Multiple items
static member TMapper.Map : i:int -> int

Full name: Script.TMapper.Map

--------------------
module Map

from Microsoft.FSharp.Collections

--------------------
type Map<'Key,'Value (requires comparison)> =
  interface IEnumerable
  interface IComparable
  interface IEnumerable<KeyValuePair<'Key,'Value>>
  interface ICollection<KeyValuePair<'Key,'Value>>
  interface IDictionary<'Key,'Value>
  new : elements:seq<'Key * 'Value> -> Map<'Key,'Value>
  member Add : key:'Key * value:'Value -> Map<'Key,'Value>
  member ContainsKey : key:'Key -> bool
  override Equals : obj -> bool
  member Remove : key:'Key -> Map<'Key,'Value>
  ...

Full name: Microsoft.FSharp.Collections.Map<_,_>

--------------------
new : elements:seq<'Key * 'Value> -> Map<'Key,'Value>

val i : int

Multiple items
val int : value:'T -> int (requires member op_Explicit)

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

--------------------
type int = int32

Full name: Microsoft.FSharp.Core.int

--------------------
type int<'Measure> = int

Full name: Microsoft.FSharp.Core.int<_>

Multiple items
union case ZeroMapper.ZeroMapper: ZeroMapper

--------------------
type ZeroMapper =
  | ZeroMapper
  static member ( $ ) : ZeroMapper:ZeroMapper * HNil:HNil -> HNil
  static member ( $ ) : ZeroMapper:ZeroMapper * HCons<string,'b> -> HCons<string,'_arg9> (requires 'b :> HList and member ( |*| ) and '_arg9 :> HList)
  static member ( $ ) : ZeroMapper:ZeroMapper * HCons<int,'a> -> HCons<int,'_arg12> (requires 'a :> HList and member ( |*| ) and '_arg12 :> HList)

Full name: Script.ZeroMapper

val x : string

val xs : 'b (requires 'b :> HList and member ( |*| ) and '_arg9 :> HList)

val x : int

val xs : 'a (requires 'a :> HList and member ( |*| ) and '_arg12 :> HList)

Multiple items
union case Length.Length: Length

--------------------
type Length =
  | Length
  static member ( $ ) : Length:Length * HNil:HNil -> Zero
  static member ( $ ) : Length:Length * HCons<'a,'b> -> Succ<'_arg7> (requires 'b :> HList and member ( |*| ) and '_arg7 :> Peano)

Full name: Script.Length

val xs : 'b (requires 'b :> HList and member ( |*| ) and '_arg7 :> Peano)

val first : HCons<int,HCons<char,HNil>>

Full name: Script.first

val second : HCons<string,HCons<bool,HNil>>

Full name: Script.second

val third : HCons<string,HCons<int,HNil>>

Full name: Script.third

val result : HCons<int,HCons<char,HCons<string,HCons<bool,HNil>>>>

Full name: Script.result

val length : Succ<Succ<Succ<Succ<Zero>>>>

Full name: Script.length

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More information

Link:	http://fssnip.net/pu
Posted:	9 years ago
Author:	Rick Minerich
Tags:	hlist , types