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Retail Domain

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open System

// Retail domain on a single page

type Name = string
type Barcode = string
type Price = decimal
type Quantity = decimal

type Product = Product of Name * Barcode * Price
type LineItem =
  | SaleLineItem of int * Product * Quantity
  | CancelLine of int 

type Basket private (items) = 
  member basket.AddItem(lineId, product, quantity) =
    let item = SaleLineItem(lineId, product, quantity)
    Basket(item::items)
  member basket.CancelLine(id) = 
    let item = CancelLine(id)
    Basket(item::items)
  member basket.Total = 
    items 
      |> List.map (fun line ->
        match line with
        | SaleLineItem(_, Product(_, _, price), quantity) ->
            price * quantity 
        | CancelLine id -> 
            items |> List.pick (fun line ->
              match line with
              | SaleLineItem(lineId, Product(_, _, price), quantity) 
                    when lineId = id -> 
                  Some(-1.0M * price * quantity)
              | _ -> None ) )    
      |> List.sum
  new() = Basket([])

// Product list and lookup

let products = 
  [ Product("Tea", "070177075101", 1.50M)
    Product("Real-World Functional Programming", "9781933988924", 49.99M) ]

let lookup searchCode = 
  products |> List.tryFind (fun (Product(_, code, _)) -> 
    code = searchCode)

// Main loop

let rec readItems lineId (basket:Basket) =
  printfn "Enter item %d: " lineId
  let search = Console.ReadLine()
  if String.IsNullOrEmpty search then 
    printfn "Total: %A" basket.Total
  elif search.StartsWith("-") then
    let id = -1 * (int search)
    readItems lineId (basket.CancelLine(id))
  else
    let prod = lookup search
    match prod with
    | Some(prod) -> 
        readItems (lineId + 1) (basket.AddItem(lineId, prod, 1.0M))
    | _ -> 
        readItems lineId basket 

readItems 0 (Basket())

namespace System

type Name = string

Full name: Script.Name

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

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

--------------------
type string = String

Full name: Microsoft.FSharp.Core.string

type Barcode = string

Full name: Script.Barcode

type Price = decimal

Full name: Script.Price

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

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

--------------------
type decimal = Decimal

Full name: Microsoft.FSharp.Core.decimal

--------------------
type decimal<'Measure> = decimal

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

type Quantity = decimal

Full name: Script.Quantity

Multiple items
union case Product.Product: Name * Barcode * Price -> Product

--------------------
type Product = | Product of Name * Barcode * Price

Full name: Script.Product

type LineItem =
| SaleLineItem of int * Product * Quantity
| CancelLine of int

Full name: Script.LineItem

union case LineItem.SaleLineItem: int * Product * Quantity -> LineItem

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<_>

union case LineItem.CancelLine: int -> LineItem

Multiple items
type Basket =
  new : unit -> Basket
  private new : items:LineItem list -> Basket
  member AddItem : lineId:int * product:Product * quantity:Quantity -> Basket
  member CancelLine : id:int -> Basket
  member Total : decimal

Full name: Script.Basket

--------------------
new : unit -> Basket
private new : items:LineItem list -> Basket

val items : LineItem list

val basket : Basket

member Basket.AddItem : lineId:int * product:Product * quantity:Quantity -> Basket

Full name: Script.Basket.AddItem

val lineId : int

val product : Product

val quantity : Quantity

val item : LineItem

member Basket.CancelLine : id:int -> Basket

Full name: Script.Basket.CancelLine

val id : int

member Basket.Total : decimal

Full name: Script.Basket.Total

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 map : mapping:('T -> 'U) -> list:'T list -> 'U list

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

val line : LineItem

val price : Price

val pick : chooser:('T -> 'U option) -> list:'T list -> 'U

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

union case Option.Some: Value: 'T -> Option<'T>

union case Option.None: Option<'T>

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

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

val products : Product list

Full name: Script.products

val lookup : searchCode:Barcode -> Product option

Full name: Script.lookup

val searchCode : Barcode

val tryFind : predicate:('T -> bool) -> list:'T list -> 'T option

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

val code : Barcode

val readItems : lineId:int -> basket:Basket -> unit

Full name: Script.readItems

val printfn : format:Printf.TextWriterFormat<'T> -> 'T

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.printfn

val search : string

type Console =
  static member BackgroundColor : ConsoleColor with get, set
  static member Beep : unit -> unit + 1 overload
  static member BufferHeight : int with get, set
  static member BufferWidth : int with get, set
  static member CapsLock : bool
  static member Clear : unit -> unit
  static member CursorLeft : int with get, set
  static member CursorSize : int with get, set
  static member CursorTop : int with get, set
  static member CursorVisible : bool with get, set
  ...

Full name: System.Console

Console.ReadLine() : string

Multiple items
type String =
  new : value:char -> string + 7 overloads
  member Chars : int -> char
  member Clone : unit -> obj
  member CompareTo : value:obj -> int + 1 overload
  member Contains : value:string -> bool
  member CopyTo : sourceIndex:int * destination:char[] * destinationIndex:int * count:int -> unit
  member EndsWith : value:string -> bool + 2 overloads
  member Equals : obj:obj -> bool + 2 overloads
  member GetEnumerator : unit -> CharEnumerator
  member GetHashCode : unit -> int
  ...

Full name: System.String

--------------------
String(value: nativeptr<char>) : unit
String(value: nativeptr<sbyte>) : unit
String(value: char []) : unit
String(c: char, count: int) : unit
String(value: nativeptr<char>, startIndex: int, length: int) : unit
String(value: nativeptr<sbyte>, startIndex: int, length: int) : unit
String(value: char [], startIndex: int, length: int) : unit
String(value: nativeptr<sbyte>, startIndex: int, length: int, enc: Text.Encoding) : unit

String.IsNullOrEmpty(value: string) : bool

property Basket.Total: decimal

String.StartsWith(value: string) : bool
String.StartsWith(value: string, comparisonType: StringComparison) : bool
String.StartsWith(value: string, ignoreCase: bool, culture: Globalization.CultureInfo) : bool

member Basket.CancelLine : id:int -> Basket

val prod : Product option

val prod : Product

member Basket.AddItem : lineId:int * product:Product * quantity:Quantity -> Basket

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