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Type-first design and implementation for a calculator app
(*
Calculator_design.fsx
Related blog post: http://fsharpforfunandprofit.com/posts/calculator-design/
*)
// ================================================
// First version of domain
// ================================================
module CalculatorDomain_V1 =
type Calculate = CalculatorInput * CalculatorState -> CalculatorState
and CalculatorState = {
display: CalculatorDisplay
}
and CalculatorDisplay = string
and CalculatorInput =
| Zero | One | Two | Three | Four
| Five | Six | Seven | Eight | Nine
| DecimalSeparator
| Add | Subtract | Multiply | Divide
| Equals | Clear
// ================================================
// Second attempt at CalculatorInput
// - move Digit to its own new type
// ================================================
module CalculatorInput_V2 =
type CalculatorDigit =
| Zero | One | Two | Three | Four
| Five | Six | Seven | Eight | Nine
| DecimalSeparator
type CalculatorInput =
| Digit of CalculatorDigit
| Add | Subtract | Multiply | Divide
| Equals | Clear
// ================================================
// Third attempt at CalculatorInput
// - move other inputs to special types as well
// ================================================
module CalculatorInput_V3 =
type CalculatorDigit =
| Zero | One | Two | Three | Four
| Five | Six | Seven | Eight | Nine
| DecimalSeparator
type CalculatorMathOp =
| Add | Subtract | Multiply | Divide
type CalculatorAction =
| Equals | Clear
type CalculatorInput =
| Digit of CalculatorDigit
| Op of CalculatorMathOp
| Action of CalculatorAction
// ================================================
// Second version of domain
//
// Added
// * UpdateDisplayFromDigit
// * DoMathOperation and related
// ================================================
module CalculatorDomain_V2 =
type Calculate = CalculatorInput * CalculatorState -> CalculatorState
and CalculatorState = {
display: CalculatorDisplay
}
and CalculatorDisplay = string
and CalculatorInput =
| Digit of CalculatorDigit
| Op of CalculatorMathOp
| Action of CalculatorAction
and CalculatorDigit =
| Zero | One | Two | Three | Four
| Five | Six | Seven | Eight | Nine
| DecimalSeparator
and CalculatorMathOp =
| Add | Subtract | Multiply | Divide
and CalculatorAction =
| Equals | Clear
type UpdateDisplayFromDigit = CalculatorDigit * CalculatorDisplay -> CalculatorDisplay
type DoMathOperation = CalculatorMathOp * Number * Number -> MathOperationResult
and Number = float
and MathOperationResult =
| Success of Number
| Failure of MathOperationError
and MathOperationError =
| DivideByZero
// ================================================
// Third version of Domain
//
// Added
// * pendingOp in CalculatorState
// * GetDisplayNumber and related
// * Services record
// ================================================
module CalculatorDomain_V3 =
type Calculate = CalculatorInput * CalculatorState -> CalculatorState
and CalculatorState = {
display: CalculatorDisplay
pendingOp: (CalculatorMathOp * Number) option
}
and CalculatorDisplay = string
and CalculatorInput =
| Digit of CalculatorDigit
| Op of CalculatorMathOp
| Action of CalculatorAction
and CalculatorDigit =
| Zero | One | Two | Three | Four
| Five | Six | Seven | Eight | Nine
| DecimalSeparator
and CalculatorMathOp =
| Add | Subtract | Multiply | Divide
and CalculatorAction =
| Equals | Clear
and UpdateDisplayFromDigit = CalculatorDigit * CalculatorDisplay -> CalculatorDisplay
and DoMathOperation = CalculatorMathOp * Number * Number -> MathOperationResult
and Number = float
and MathOperationResult =
| Success of Number
| Failure of MathOperationError
and MathOperationError =
| DivideByZero
type GetDisplayNumber = CalculatorDisplay -> Number option
type SetDisplayNumber = Number -> CalculatorDisplay
type SetDisplayError = MathOperationError -> CalculatorDisplay
type InitState = unit -> CalculatorState
type CalculatorServices = {
updateDisplayFromDigit: UpdateDisplayFromDigit
doMathOperation: DoMathOperation
getDisplayNumber: GetDisplayNumber
setDisplayNumber: SetDisplayNumber
setDisplayError: SetDisplayError
initState: InitState
}
// ================================================
// Example of how bootstrapper code would work
// with services
// ================================================
(*
// assemble everything
open CalculatorDomain
open System
let services = CalculatorServices.createServices()
let initState = services.initState
let calculate = CalculatorImplementation.createCalculate services
let form = new CalculatorUI.CalculatorForm(initState,calculate)
form.Show()
*)
(*
Calculator_implementation.fsx
Related blog post: http://fsharpforfunandprofit.com/posts/calculator-implementation/
*)
// ================================================
// Draft of Domain from previous file
// ================================================
module CalculatorDomain_V3 =
type Calculate = CalculatorInput * CalculatorState -> CalculatorState
and CalculatorState = {
display: CalculatorDisplay
pendingOp: (CalculatorMathOp * Number) option
}
and CalculatorDisplay = string
and CalculatorInput =
| Digit of CalculatorDigit
| Op of CalculatorMathOp
| Action of CalculatorAction
and CalculatorDigit =
| Zero | One | Two | Three | Four
| Five | Six | Seven | Eight | Nine
| DecimalSeparator
and CalculatorMathOp =
| Add | Subtract | Multiply | Divide
and CalculatorAction =
| Equals | Clear
and UpdateDisplayFromDigit = CalculatorDigit * CalculatorDisplay -> CalculatorDisplay
and DoMathOperation = CalculatorMathOp * Number * Number -> MathOperationResult
and Number = float
and MathOperationResult =
| Success of Number
| Failure of MathOperationError
and MathOperationError =
| DivideByZero
type GetDisplayNumber = CalculatorDisplay -> Number option
type SetDisplayNumber = Number -> CalculatorDisplay
// added when missing requirement for error display needed
type SetDisplayError = MathOperationError -> CalculatorDisplay
type InitState = unit -> CalculatorState
type CalculatorServices = {
updateDisplayFromDigit: UpdateDisplayFromDigit
doMathOperation: DoMathOperation
getDisplayNumber: GetDisplayNumber
setDisplayNumber: SetDisplayNumber
setDisplayError: SetDisplayError // added for missing requirement
initState: InitState
}
// ================================================
// Utilities
// ================================================
[<AutoOpen>]
module CommonComputationExpressions =
type MaybeBuilder() =
member this.Bind(x, f) = Option.bind f x
member this.Return(x) = Some x
let maybe = new MaybeBuilder()
// ================================================
// First implementation of Calculator
// ================================================
module CalculatorImplementation_V1 =
open CalculatorDomain_V3
let updateDisplayFromDigit services digit state =
let newDisplay = services.updateDisplayFromDigit (digit,state.display)
let newState = {state with display=newDisplay}
newState //return
// First version of updateDisplayFromPendingOp
// * very imperative and ugly
let updateDisplayFromPendingOp services state =
if state.pendingOp.IsSome then
let op,pendingNumber = state.pendingOp.Value
let currentNumberOpt = services.getDisplayNumber state.display
if currentNumberOpt.IsSome then
let currentNumber = currentNumberOpt.Value
let result = services.doMathOperation (op,pendingNumber,currentNumber)
match result with
| Success resultNumber ->
let newDisplay = services.setDisplayNumber resultNumber
let newState = {display=newDisplay;pendingOp=None}
newState //return
| Failure error ->
state // original state is untouched
else
state // original state is untouched
else
state // original state is untouched
// Second version of updateDisplayFromPendingOp
// * Uses "bind"
// * Doesn't show errors on display in Failure case
let updateDisplayFromPendingOp_v2 services state =
// helper to extract CurrentNumber
let getCurrentNumber (op,pendingNumber) =
state.display
|> services.getDisplayNumber
|> Option.map (fun currentNumber -> (op,pendingNumber,currentNumber))
// helper to do the math op
let doMathOp (op,pendingNumber,currentNumber) =
let result = services.doMathOperation (op,pendingNumber,currentNumber)
match result with
| Success resultNumber ->
let newDisplay = services.setDisplayNumber resultNumber
let newState = {display=newDisplay;pendingOp=None}
Some newState //return something
| Failure error ->
None // failed
// connect all the helpers
state.pendingOp
|> Option.bind getCurrentNumber
|> Option.bind doMathOp
|> defaultArg <| state
// helper to make defaultArg better for piping
let ifNone defaultValue input =
// just reverse the parameters!
defaultArg input defaultValue
// Third version of updateDisplayFromPendingOp
// * Updated to show errors on display in Failure case
// * replaces awkward defaultArg syntax
let updateDisplayFromPendingOp_v3 services state =
// helper to extract CurrentNumber
let getCurrentNumber (op,pendingNumber) =
state.display
|> services.getDisplayNumber
|> Option.map (fun currentNumber -> (op,pendingNumber,currentNumber))
// helper to do the math op
let doMathOp (op,pendingNumber,currentNumber) =
let result = services.doMathOperation (op,pendingNumber,currentNumber)
let newDisplay =
match result with
| Success resultNumber ->
services.setDisplayNumber resultNumber
| Failure error ->
services.setDisplayError error
let newState = {display=newDisplay;pendingOp=None}
Some newState //return something
// connect all the helpers
state.pendingOp
|> Option.bind getCurrentNumber
|> Option.bind doMathOp
|> ifNone state // return original state if anything fails
// Fourth version of updateDisplayFromPendingOp
// * Changed to use "maybe" computation expression
let updateDisplayFromPendingOp_v4 services state =
// helper to do the math op
let doMathOp (op,pendingNumber,currentNumber) =
let result = services.doMathOperation (op,pendingNumber,currentNumber)
let newDisplay =
match result with
| Success resultNumber ->
services.setDisplayNumber resultNumber
| Failure error ->
services.setDisplayError error
{display=newDisplay;pendingOp=None}
// fetch the two options and combine them
let newState = maybe {
let! (op,pendingNumber) = state.pendingOp
let! currentNumber = services.getDisplayNumber state.display
return doMathOp (op,pendingNumber,currentNumber)
}
newState |> ifNone state
// First version of addPendingMathOp
// * very imperative and ugly
let addPendingMathOp services op state =
let currentNumberOpt = services.getDisplayNumber state.display
if currentNumberOpt.IsSome then
let currentNumber = currentNumberOpt.Value
let pendingOp = Some (op,currentNumber)
let newState = {state with pendingOp=pendingOp}
newState //return
else
state // original state is untouched
// Second version of addPendingMathOp
// * Uses "map" and helper function
let addPendingMathOp_v2 services op state =
let newStateWithPending currentNumber =
let pendingOp = Some (op,currentNumber)
{state with pendingOp=pendingOp}
state.display
|> services.getDisplayNumber
|> Option.map newStateWithPending
|> ifNone state
// Third version of addPendingMathOp
// * Uses "maybe"
let addPendingMathOp_v3 services op state =
maybe {
let! currentNumber =
state.display |> services.getDisplayNumber
let pendingOp = Some (op,currentNumber)
return {state with pendingOp=pendingOp}
}
|> ifNone state // return original state if anything fails
// creates a calculate function
let createCalculate (services:CalculatorServices) :Calculate =
fun (input,state) ->
match input with
| Digit d ->
let newState = updateDisplayFromDigit services d state
newState //return
| Op op ->
let newState1 = updateDisplayFromPendingOp services state
let newState2 = addPendingMathOp services op newState1
newState2 //return
| Action Clear ->
let newState = services.initState()
newState //return
| Action Equals ->
let newState = updateDisplayFromPendingOp services state
newState //return
/// Alternate version of createCalculate that uses an inner function rather than a lambda
let createCalculate_V2 (services:CalculatorServices) :Calculate =
let innerCalculate (input,state) =
match input with
| Digit d -> state // not implemented
| Op op -> state // not implemented
| Action Clear -> state // not implemented
| Action Equals -> state // not implemented
innerCalculate // return the inner function
// ================================================
// Example of how bootstrapper code would work
// with services
// ================================================
(*
// assemble everything
open CalculatorDomain
open System
let services = CalculatorServices.createServices()
let initState = services.initState
let calculate = CalculatorImplementation.createCalculate services
let form = new CalculatorUI.CalculatorForm(initState,calculate)
form.Show()
*)
(*
Calculator_v1.fsx
Related blog post: http://fsharpforfunandprofit.com/posts/calculator-complete-v1/
*)
// ================================================
// Domain
// ================================================
module CalculatorDomain =
type Calculate = CalculatorInput * CalculatorState -> CalculatorState
and CalculatorState = {
display: CalculatorDisplay
pendingOp: (CalculatorMathOp * Number) option
}
and CalculatorDisplay = string
and CalculatorInput =
| Digit of CalculatorDigit
| Op of CalculatorMathOp
| Action of CalculatorAction
and CalculatorDigit =
| Zero | One | Two | Three | Four
| Five | Six | Seven | Eight | Nine
| DecimalSeparator
and CalculatorMathOp =
| Add | Subtract | Multiply | Divide
and CalculatorAction =
| Equals | Clear
and UpdateDisplayFromDigit = CalculatorDigit * CalculatorDisplay -> CalculatorDisplay
and DoMathOperation = CalculatorMathOp * Number * Number -> MathOperationResult
and Number = float
and MathOperationResult =
| Success of Number
| Failure of MathOperationError
and MathOperationError =
| DivideByZero
type GetDisplayNumber = CalculatorDisplay -> Number option
type SetDisplayNumber = Number -> CalculatorDisplay
type SetDisplayError = MathOperationError -> CalculatorDisplay
type InitState = unit -> CalculatorState
type CalculatorServices = {
updateDisplayFromDigit: UpdateDisplayFromDigit
doMathOperation: DoMathOperation
getDisplayNumber: GetDisplayNumber
setDisplayNumber: SetDisplayNumber
setDisplayError: SetDisplayError
initState: InitState
}
// ================================================
// Utilities
// ================================================
[<AutoOpen>]
module CommonComputationExpressions =
type MaybeBuilder() =
member this.Bind(x, f) = Option.bind f x
member this.Return(x) = Some x
let maybe = new MaybeBuilder()
// ================================================
// Implementation of Calculator
// ================================================
module CalculatorImplementation =
open CalculatorDomain
// helper to make defaultArg better for piping
let ifNone defaultValue input =
// just reverse the parameters!
defaultArg input defaultValue
let updateDisplayFromDigit services digit state =
let newDisplay = services.updateDisplayFromDigit (digit,state.display)
let newState = {state with display=newDisplay}
newState //return
let updateDisplayFromPendingOp services state =
// helper to do the math op
let doMathOp (op,pendingNumber,currentNumber) =
let result = services.doMathOperation (op,pendingNumber,currentNumber)
let newDisplay =
match result with
| Success resultNumber ->
services.setDisplayNumber resultNumber
| Failure error ->
services.setDisplayError error
{display=newDisplay;pendingOp=None}
// fetch the two options and combine them
let newState = maybe {
let! (op,pendingNumber) = state.pendingOp
let! currentNumber = services.getDisplayNumber state.display
return doMathOp (op,pendingNumber,currentNumber)
}
newState |> ifNone state
let addPendingMathOp services op state =
maybe {
let! currentNumber =
state.display |> services.getDisplayNumber
let pendingOp = Some (op,currentNumber)
return {state with pendingOp=pendingOp}
}
|> ifNone state // return original state if anything fails
let createCalculate (services:CalculatorServices) :Calculate =
fun (input,state) ->
match input with
| Digit d ->
let newState = updateDisplayFromDigit services d state
newState //return
| Op op ->
let newState1 = updateDisplayFromPendingOp services state
let newState2 = addPendingMathOp services op newState1
newState2 //return
| Action Clear ->
let newState = services.initState()
newState //return
| Action Equals ->
let newState = updateDisplayFromPendingOp services state
newState //return
// ================================================
// Implementation of CalculatorConfiguration
// ================================================
module CalculatorConfiguration =
// A record to store configuration options
// (e.g. loaded from a file or environment)
type Configuration = {
decimalSeparator : string
divideByZeroMsg : string
maxDisplayLength: int
}
let loadConfig() = {
decimalSeparator =
System.Globalization.CultureInfo.CurrentCulture.NumberFormat.CurrencyDecimalSeparator
divideByZeroMsg = "ERR-DIV0"
maxDisplayLength = 10
}
// ================================================
// Implementation of CalculatorServices
// ================================================
module CalculatorServices =
open CalculatorDomain
open CalculatorConfiguration
let updateDisplayFromDigit (config:Configuration) :UpdateDisplayFromDigit =
fun (digit, display) ->
// determine what character should be appended to the display
let appendCh=
match digit with
| Zero ->
// only allow one 0 at start of display
if display="0" then "" else "0"
| One -> "1"
| Two -> "2"
| Three-> "3"
| Four -> "4"
| Five -> "5"
| Six-> "6"
| Seven-> "7"
| Eight-> "8"
| Nine-> "9"
| DecimalSeparator ->
if display="" then
// handle empty display with special case
"0" + config.decimalSeparator
else if display.Contains(config.decimalSeparator) then
// don't allow two decimal separators
""
else
config.decimalSeparator
// ignore new input if there are too many digits
if (display.Length > config.maxDisplayLength) then
display // ignore new input
else
// append the new char
display + appendCh
let getDisplayNumber :GetDisplayNumber = fun display ->
match System.Double.TryParse display with
| true, d -> Some d
| false, _ -> None
let setDisplayNumber :SetDisplayNumber = fun f ->
sprintf "%g" f
let setDisplayError divideByZeroMsg :SetDisplayError = fun f ->
match f with
| DivideByZero -> divideByZeroMsg
let doMathOperation :DoMathOperation = fun (op,f1,f2) ->
match op with
| Add -> Success (f1 + f2)
| Subtract -> Success (f1 - f2)
| Multiply -> Success (f1 * f2)
| Divide ->
try
Success (f1 / f2)
with
| :? System.DivideByZeroException ->
Failure DivideByZero
let initState :InitState = fun () ->
{
display=""
pendingOp = None
}
let createServices (config:Configuration) = {
updateDisplayFromDigit = updateDisplayFromDigit config
doMathOperation = doMathOperation
getDisplayNumber = getDisplayNumber
setDisplayNumber = setDisplayNumber
setDisplayError = setDisplayError (config.divideByZeroMsg)
initState = initState
}
// ================================================
// Implementation of Calculator UI
// ================================================
module CalculatorUI =
open System
open System.Drawing
open System.Drawing.Drawing2D
open System.Windows.Forms
open CalculatorDomain
type CalculatorForm(initState:InitState, calculate:Calculate) as this =
inherit Form()
// constants
let margin = 20
let buttonDimension = 50
let buttonPadding = 10
let doubleDimension = buttonDimension + buttonPadding + buttonDimension
let gridSize = buttonDimension + buttonPadding
let buttonSize = Size(buttonDimension,buttonDimension)
let doubleWidthSize = Size(doubleDimension,buttonDimension)
let doubleHeightSize = Size(buttonDimension,doubleDimension)
let decimalSeparator = System.Globalization.CultureInfo.CurrentCulture.NumberFormat.CurrencyDecimalSeparator
let DigitButtonColor = Color.White
let OpButtonColor = Color.PeachPuff
let DangerButtonColor = Color.Coral
// initialization before constructor
let mutable state = initState()
// a function that sets the displayed text
let mutable setDisplayedText =
fun text -> () // do nothing
// traditional style -- have a label control as a field
// let mutable displayControl :Label = null
// ========================
// private helper functions
// ========================
/// Get the physical location, given a row and column.
/// Row/col are 0-based
let getPos(row,col) =
let x = margin + (col*gridSize)
let y = margin + (row* gridSize)
Point(x,y)
let handleInput input =
let newState = calculate(input,state)
state <- newState
setDisplayedText state.display
let handleDigit digit =
Digit digit |> handleInput
let handleOp op =
Op op |> handleInput
let handleAction action =
Action action |> handleInput
// ========================
// initialization in constructor
// ========================
do
this.SetupForm()
// ========================
// Public methods
// ========================
/// Use a member rather than a let-bound function so it can be called from the constructor
member this.SetupForm() =
this.Text <- "Calculator"
this.Font <- new Font(FontFamily.GenericSansSerif,14.f)
let clientSizeX = (2*margin) + (5*buttonDimension) + (4*buttonPadding)
let clientSizeY = (2*margin) + (5*buttonDimension) + (4*buttonPadding)
this.ClientSize <- Size(clientSizeX,clientSizeY)
this.CenterToScreen()
let keyPressHandler = new KeyPressEventHandler(fun obj e -> this.KeyPressHandler(e))
this.KeyPress.AddHandler keyPressHandler
this.KeyPreview <- true // let the form handle key events
this.CreateButtons()
this.CreateDisplayLabel()
/// Create a member rather than let-bound so it can be called from constructor
member this.CreateDisplayLabel() =
let displayWidth = 5*buttonDimension + 4*buttonPadding
let displaySize = Size(displayWidth,buttonDimension)
let display = new Label(Text="",Size=displaySize,Location=getPos(0,0))
display.TextAlign <- ContentAlignment.MiddleRight
display.BackColor <- Color.White
this.Controls.Add(display)
// update the function that sets the text
setDisplayedText <-
(fun text -> display.Text <- text)
// traditional style - set the field when the form has been initialized
// displayControl <- display
/// Create a member rather than let-bound so it can be called from constructor
member this.CreateButtons() =
let addDigitButton digit (button:Button) =
button.Click.AddHandler(EventHandler(fun _ _ -> handleDigit digit))
this.Controls.Add(button)
let addOpButton op (button:Button) =
button.Click.AddHandler(EventHandler(fun _ _ -> handleOp op))
this.Controls.Add(button)
let addActionButton misc (button:Button) =
button.Click.AddHandler(EventHandler(fun _ _ -> handleAction misc))
this.Controls.Add(button)
let sevenButton = new Button(Text="7",Size=buttonSize,Location=getPos(1,0),BackColor=DigitButtonColor)
sevenButton |> addDigitButton Seven
let eightButton = new Button(Text="8",Size=buttonSize,Location=getPos(1,1),BackColor=DigitButtonColor)
eightButton |> addDigitButton Eight
let nineButton = new Button(Text="9",Size=buttonSize,Location=getPos(1,2),BackColor=DigitButtonColor)
nineButton |> addDigitButton Nine
let clearButton = new Button(Text="C",Size=buttonSize,Location=getPos(1,3),BackColor=DangerButtonColor)
clearButton |> addActionButton Clear
let addButton = new Button(Text="+",Size=doubleHeightSize,Location=getPos(1,4),BackColor=OpButtonColor)
addButton |> addOpButton Add
let fourButton = new Button(Text="4",Size=buttonSize,Location=getPos(2,0),BackColor=DigitButtonColor)
fourButton |> addDigitButton Four
let fiveButton = new Button(Text="5",Size=buttonSize,Location=getPos(2,1),BackColor=DigitButtonColor)
fiveButton |> addDigitButton Five
let sixButton = new Button(Text="6",Size=buttonSize,Location=getPos(2,2),BackColor=DigitButtonColor)
sixButton |> addDigitButton Six
let divideButton = new Button(Text="/",Size=buttonSize,Location=getPos(2,3),BackColor=OpButtonColor)
divideButton |> addOpButton Divide
let oneButton = new Button(Text="1",Size=buttonSize,Location=getPos(3,0),BackColor=DigitButtonColor)
oneButton |> addDigitButton One
let twoButton = new Button(Text="2",Size=buttonSize,Location=getPos(3,1),BackColor=DigitButtonColor)
twoButton |> addDigitButton Two
let threeButton = new Button(Text="3",Size=buttonSize,Location=getPos(3,2),BackColor=DigitButtonColor)
threeButton |> addDigitButton Three
let multButton = new Button(Text="*",Size=buttonSize,Location=getPos(3,3),BackColor=OpButtonColor)
multButton |> addOpButton Multiply
let equalButton = new Button(Text="=",Size=doubleHeightSize,Location=getPos(3,4),BackColor=OpButtonColor)
equalButton |> addActionButton Equals
let zeroButton = new Button(Text="0",Size=doubleWidthSize,Location=getPos(4,0),BackColor=DigitButtonColor)
zeroButton |> addDigitButton Zero
let pointButton = new Button(Text=decimalSeparator,Size=buttonSize,Location=getPos(4,2),BackColor=DigitButtonColor)
pointButton |> addDigitButton DecimalSeparator
let minusButton = new Button(Text="-",Size=buttonSize,Location=getPos(4,3),BackColor=OpButtonColor)
minusButton |> addOpButton Subtract
member this.KeyPressHandler(e:KeyPressEventArgs) =
match e.KeyChar with
| '0' -> handleDigit Zero
| '1' -> handleDigit One
| '2' -> handleDigit Two
| '3' -> handleDigit Three
| '4' -> handleDigit Four
| '5' -> handleDigit Five
| '6' -> handleDigit Six
| '7' -> handleDigit Seven
| '8' -> handleDigit Eight
| '9' -> handleDigit Nine
| '.' | ',' -> handleDigit DecimalSeparator
| '+' -> handleOp Add
| '-' -> handleOp Subtract
| '/' -> handleOp Divide
| '*' -> handleOp Multiply
| '=' | '\n' | '\r' -> handleAction Equals
| 'C' | 'c' -> handleAction Clear
| _ -> ()
// ================================================
// Bootstrapper
// ================================================
// assemble everything
open CalculatorDomain
open System
let config = CalculatorConfiguration.loadConfig()
let services = CalculatorServices.createServices config
let initState = services.initState
let calculate = CalculatorImplementation.createCalculate services
let form = new CalculatorUI.CalculatorForm(initState,calculate)
form.Show()
(*
Calculator_v1_patched.fsx
Related blog post: http://fsharpforfunandprofit.com/posts/calculator-complete-v1/
*)
// ================================================
// Patched implementation of Domain
// ================================================
module CalculatorDomain =
type Calculate = CalculatorInput * CalculatorState -> CalculatorState
and CalculatorState = {
display: CalculatorDisplay
pendingOp: (CalculatorMathOp * Number) option
allowAppend: bool
}
and CalculatorDisplay = string
and CalculatorInput =
| Digit of CalculatorDigit
| Op of CalculatorMathOp
| Action of CalculatorAction
and CalculatorDigit =
| Zero | One | Two | Three | Four
| Five | Six | Seven | Eight | Nine
| DecimalSeparator
and CalculatorMathOp =
| Add | Subtract | Multiply | Divide
and CalculatorAction =
| Equals | Clear
and UpdateDisplayFromDigit = CalculatorDigit * CalculatorDisplay -> CalculatorDisplay
and DoMathOperation = CalculatorMathOp * Number * Number -> MathOperationResult
and Number = float
and MathOperationResult =
| Success of Number
| Failure of MathOperationError
and MathOperationError =
| DivideByZero
type GetDisplayNumber = CalculatorDisplay -> Number option
type SetDisplayNumber = Number -> CalculatorDisplay
type SetDisplayError = MathOperationError -> CalculatorDisplay
type InitState = unit -> CalculatorState
type CalculatorServices = {
updateDisplayFromDigit: UpdateDisplayFromDigit
doMathOperation: DoMathOperation
getDisplayNumber: GetDisplayNumber
setDisplayNumber: SetDisplayNumber
setDisplayError: SetDisplayError
initState: InitState
}
// ================================================
// Utilities
// ================================================
[<AutoOpen>]
module CommonComputationExpressions =
type MaybeBuilder() =
member this.Bind(x, f) = Option.bind f x
member this.Return(x) = Some x
let maybe = new MaybeBuilder()
// ================================================
// Implementation of Calculator
// ================================================
module CalculatorImplementation =
open CalculatorDomain
// helper to make defaultArg better for piping
let ifNone defaultValue input =
// just reverse the parameters!
defaultArg input defaultValue
let updateDisplayFromDigit services digit state =
let buffer =
if state.allowAppend then
state.display
else
""
let newDisplay = services.updateDisplayFromDigit (digit,buffer)
let newState = {state with display=newDisplay; allowAppend=true}
newState //return
let updateDisplayFromPendingOp services state =
// helper to do the math op
let doMathOp (op,pendingNumber,currentNumber) =
let result = services.doMathOperation (op,pendingNumber,currentNumber)
let newDisplay =
match result with
| Success resultNumber ->
services.setDisplayNumber resultNumber
| Failure error ->
services.setDisplayError error
{display=newDisplay; pendingOp=None; allowAppend=false}
// fetch the two options and combine them
let newState = maybe {
let! (op,pendingNumber) = state.pendingOp
let! currentNumber = services.getDisplayNumber state.display
return doMathOp (op,pendingNumber,currentNumber)
}
newState |> ifNone state
let addPendingMathOp services op state =
maybe {
let! currentNumber =
state.display |> services.getDisplayNumber
let pendingOp = Some (op,currentNumber)
return {state with pendingOp=pendingOp; allowAppend=false}
}
|> ifNone state // return original state if anything fails
let createCalculate (services:CalculatorServices) :Calculate =
fun (input,state) ->
match input with
| Digit d ->
let newState = updateDisplayFromDigit services d state
newState //return
| Op op ->
let newState1 = updateDisplayFromPendingOp services state
let newState2 = addPendingMathOp services op newState1
newState2 //return
| Action Clear ->
let newState = services.initState()
newState //return
| Action Equals ->
let newState = updateDisplayFromPendingOp services state
newState //return
// ================================================
// Implementation of CalculatorConfiguration
// ================================================
module CalculatorConfiguration =
// A record to store configuration options
// (e.g. loaded from a file or environment)
type Configuration = {
decimalSeparator : string
divideByZeroMsg : string
maxDisplayLength: int
}
let loadConfig() = {
decimalSeparator =
System.Globalization.CultureInfo.CurrentCulture.NumberFormat.CurrencyDecimalSeparator
divideByZeroMsg = "ERR-DIV0"
maxDisplayLength = 10
}
// ================================================
// Implementation of CalculatorServices
// ================================================
module CalculatorServices =
open CalculatorDomain
open CalculatorConfiguration
let updateDisplayFromDigit (config:Configuration) :UpdateDisplayFromDigit =
fun (digit, display) ->
// determine what character should be appended to the display
let appendCh=
match digit with
| Zero ->
// only allow one 0 at start of display
if display="0" then "" else "0"
| One -> "1"
| Two -> "2"
| Three-> "3"
| Four -> "4"
| Five -> "5"
| Six-> "6"
| Seven-> "7"
| Eight-> "8"
| Nine-> "9"
| DecimalSeparator ->
if display="" then
// handle empty display with special case
"0" + config.decimalSeparator
else if display.Contains(config.decimalSeparator) then
// don't allow two decimal separators
""
else
config.decimalSeparator
// ignore new input if there are too many digits
if (display.Length > config.maxDisplayLength) then
display // ignore new input
else
// append the new char
display + appendCh
let getDisplayNumber :GetDisplayNumber = fun display ->
match System.Double.TryParse display with
| true, d -> Some d
| false, _ -> None
let setDisplayNumber :SetDisplayNumber = fun f ->
sprintf "%g" f
let setDisplayError divideByZeroMsg :SetDisplayError = fun f ->
match f with
| DivideByZero -> divideByZeroMsg
let doMathOperation :DoMathOperation = fun (op,f1,f2) ->
match op with
| Add -> Success (f1 + f2)
| Subtract -> Success (f1 - f2)
| Multiply -> Success (f1 * f2)
| Divide ->
try
Success (f1 / f2)
with
| :? System.DivideByZeroException ->
Failure DivideByZero
let initState :InitState = fun () ->
{
display=""
pendingOp = None
allowAppend = true
}
let createServices (config:Configuration) = {
updateDisplayFromDigit = updateDisplayFromDigit config
doMathOperation = doMathOperation
getDisplayNumber = getDisplayNumber
setDisplayNumber = setDisplayNumber
setDisplayError = setDisplayError (config.divideByZeroMsg)
initState = initState
}
// ================================================
// Implementation of Calculator UI
// ================================================
module CalculatorUI =
open System
open System.Drawing
open System.Drawing.Drawing2D
open System.Windows.Forms
open CalculatorDomain
type CalculatorForm(initState:InitState, calculate:Calculate) as this =
inherit Form()
// constants
let margin = 20
let buttonDimension = 50
let buttonPadding = 10
let doubleDimension = buttonDimension + buttonPadding + buttonDimension
let gridSize = buttonDimension + buttonPadding
let buttonSize = Size(buttonDimension,buttonDimension)
let doubleWidthSize = Size(doubleDimension,buttonDimension)
let doubleHeightSize = Size(buttonDimension,doubleDimension)
let decimalSeparator = System.Globalization.CultureInfo.CurrentCulture.NumberFormat.CurrencyDecimalSeparator
let DigitButtonColor = Color.White
let OpButtonColor = Color.PeachPuff
let DangerButtonColor = Color.Coral
// initialization before constructor
let mutable state = initState()
// a function that sets the displayed text
let mutable setDisplayedText =
fun text -> () // do nothing
// traditional style -- have a label control as a field
// let mutable displayControl :Label = null
// ========================
// private helper functions
// ========================
/// Get the physical location, given a row and column.
/// Row/col are 0-based
let getPos(row,col) =
let x = margin + (col*gridSize)
let y = margin + (row* gridSize)
Point(x,y)
let handleInput input =
let newState = calculate(input,state)
state <- newState
setDisplayedText state.display
let handleDigit digit =
Digit digit |> handleInput
let handleOp op =
Op op |> handleInput
let handleAction action =
Action action |> handleInput
// ========================
// initialization in constructor
// ========================
do
this.SetupForm()
// ========================
// Public methods
// ========================
/// Create a member rather than let-bound so it can be called from constructor
member this.SetupForm() =
this.Text <- "Calculator"
this.Font <- new Font(FontFamily.GenericSansSerif,14.f)
let clientSizeX = (2*margin) + (5*buttonDimension) + (4*buttonPadding)
let clientSizeY = (2*margin) + (5*buttonDimension) + (4*buttonPadding)
this.ClientSize <- Size(clientSizeX,clientSizeY)
this.CenterToScreen()
let keyPressHandler = new KeyPressEventHandler(fun obj e -> this.KeyPressHandler(e))
this.KeyPress.AddHandler keyPressHandler
this.KeyPreview <- true // let the form handle key events
this.CreateButtons()
this.CreateDisplayLabel()
/// Use a member rather than a let-bound function so it can be called from the constructor
member this.CreateDisplayLabel() =
let displayWidth = 5*buttonDimension + 4*buttonPadding
let displaySize = Size(displayWidth,buttonDimension)
let display = new Label(Text="",Size=displaySize,Location=getPos(0,0))
display.TextAlign <- ContentAlignment.MiddleRight
display.BackColor <- Color.White
this.Controls.Add(display)
// update the function that sets the text
setDisplayedText <-
(fun text -> display.Text <- text)
// traditional style - set the field when the form has been initialized
// displayControl <- display
/// Use a member rather than a let-bound function so it can be called from the constructor
member this.CreateButtons() =
let addDigitButton digit (button:Button) =
button.Click.AddHandler(EventHandler(fun _ _ -> handleDigit digit))
this.Controls.Add(button)
let addOpButton op (button:Button) =
button.Click.AddHandler(EventHandler(fun _ _ -> handleOp op))
this.Controls.Add(button)
let addActionButton misc (button:Button) =
button.Click.AddHandler(EventHandler(fun _ _ -> handleAction misc))
this.Controls.Add(button)
let sevenButton = new Button(Text="7",Size=buttonSize,Location=getPos(1,0),BackColor=DigitButtonColor)
sevenButton |> addDigitButton Seven
let eightButton = new Button(Text="8",Size=buttonSize,Location=getPos(1,1),BackColor=DigitButtonColor)
eightButton |> addDigitButton Eight
let nineButton = new Button(Text="9",Size=buttonSize,Location=getPos(1,2),BackColor=DigitButtonColor)
nineButton |> addDigitButton Nine
let clearButton = new Button(Text="C",Size=buttonSize,Location=getPos(1,3),BackColor=DangerButtonColor)
clearButton |> addActionButton Clear
let addButton = new Button(Text="+",Size=doubleHeightSize,Location=getPos(1,4),BackColor=OpButtonColor)
addButton |> addOpButton Add
let fourButton = new Button(Text="4",Size=buttonSize,Location=getPos(2,0),BackColor=DigitButtonColor)
fourButton |> addDigitButton Four
let fiveButton = new Button(Text="5",Size=buttonSize,Location=getPos(2,1),BackColor=DigitButtonColor)
fiveButton |> addDigitButton Five
let sixButton = new Button(Text="6",Size=buttonSize,Location=getPos(2,2),BackColor=DigitButtonColor)
sixButton |> addDigitButton Six
let divideButton = new Button(Text="/",Size=buttonSize,Location=getPos(2,3),BackColor=OpButtonColor)
divideButton |> addOpButton Divide
let oneButton = new Button(Text="1",Size=buttonSize,Location=getPos(3,0),BackColor=DigitButtonColor)
oneButton |> addDigitButton One
let twoButton = new Button(Text="2",Size=buttonSize,Location=getPos(3,1),BackColor=DigitButtonColor)
twoButton |> addDigitButton Two
let threeButton = new Button(Text="3",Size=buttonSize,Location=getPos(3,2),BackColor=DigitButtonColor)
threeButton |> addDigitButton Three
let multButton = new Button(Text="*",Size=buttonSize,Location=getPos(3,3),BackColor=OpButtonColor)
multButton |> addOpButton Multiply
let equalButton = new Button(Text="=",Size=doubleHeightSize,Location=getPos(3,4),BackColor=OpButtonColor)
equalButton |> addActionButton Equals
let zeroButton = new Button(Text="0",Size=doubleWidthSize,Location=getPos(4,0),BackColor=DigitButtonColor)
zeroButton |> addDigitButton Zero
let pointButton = new Button(Text=decimalSeparator,Size=buttonSize,Location=getPos(4,2),BackColor=DigitButtonColor)
pointButton |> addDigitButton DecimalSeparator
let minusButton = new Button(Text="-",Size=buttonSize,Location=getPos(4,3),BackColor=OpButtonColor)
minusButton |> addOpButton Subtract
member this.KeyPressHandler(e:KeyPressEventArgs) =
match e.KeyChar with
| '0' -> handleDigit Zero
| '1' -> handleDigit One
| '2' -> handleDigit Two
| '3' -> handleDigit Three
| '4' -> handleDigit Four
| '5' -> handleDigit Five
| '6' -> handleDigit Six
| '7' -> handleDigit Seven
| '8' -> handleDigit Eight
| '9' -> handleDigit Nine
| '.' | ',' -> handleDigit DecimalSeparator
| '+' -> handleOp Add
| '-' -> handleOp Subtract
| '/' -> handleOp Divide
| '*' -> handleOp Multiply
| '=' | '\n' | '\r' -> handleAction Equals
| 'C' | 'c' -> handleAction Clear
| _ -> ()
// ================================================
// Tests
// ================================================
module CalculatorTests =
open CalculatorDomain
open System
let config = CalculatorConfiguration.loadConfig()
let services = CalculatorServices.createServices config
let calculate = CalculatorImplementation.createCalculate services
let emptyState = services.initState()
/// Given a sequence of inputs, start with the empty state
/// and apply each input in turn. The final state is returned
let processInputs inputs =
// helper for fold
let folder state input =
calculate(input,state)
inputs
|> List.fold folder emptyState
/// Check that the state contains the expected display value
let assertResult testLabel expected state =
let actual = state.display
if (expected <> actual) then
printfn "Test %s failed: expected=%s actual=%s" testLabel expected actual
else
printfn "Test %s passed" testLabel
let ``when I input 1 + 2, I expect 3``() =
[Digit One; Op Add; Digit Two; Action Equals]
|> processInputs
|> assertResult "1+2=3" "3"
let ``when I input 1 + 2 + 3, I expect 6``() =
[Digit One; Op Add; Digit Two; Op Add; Digit Three; Action Equals]
|> processInputs
|> assertResult "1+2+3=6" "6"
// run tests
do
``when I input 1 + 2, I expect 3``()
``when I input 1 + 2 + 3, I expect 6``()
// ================================================
// Bootstrapper
// ================================================
// assemble everything
open CalculatorDomain
open System
let config = CalculatorConfiguration.loadConfig()
let services = CalculatorServices.createServices config
let initState = services.initState
let calculate = CalculatorImplementation.createCalculate services
let form = new CalculatorUI.CalculatorForm(initState,calculate)
form.Show()
(*
Calculator_v2.fsx
Related blog post: http://fsharpforfunandprofit.com/posts/calculator-complete-v2/
*)
// ================================================
// Domain using a state machine
// ================================================
module CalculatorDomain =
type Calculate = CalculatorInput * CalculatorState -> CalculatorState
// five states
and CalculatorState =
| ZeroState of ZeroStateData
| AccumulatorState of AccumulatorStateData
| AccumulatorWithDecimalState of AccumulatorStateData
| ComputedState of ComputedStateData
| ErrorState of ErrorStateData
// six inputs
and CalculatorInput =
| Zero
| Digit of NonZeroDigit
| DecimalSeparator
| MathOp of CalculatorMathOp
| Equals
| Clear
// data associated with each state
and ZeroStateData =
PendingOp option
and AccumulatorStateData =
{digits:DigitAccumulator; pendingOp:PendingOp option}
and ComputedStateData =
{displayNumber:Number; pendingOp:PendingOp option}
and ErrorStateData =
MathOperationError
// other types referenced from above
and DigitAccumulator = string
and PendingOp = (CalculatorMathOp * Number)
and Number = float
and NonZeroDigit=
| One | Two | Three | Four
| Five | Six | Seven | Eight | Nine
and CalculatorMathOp =
| Add | Subtract | Multiply | Divide
and MathOperationResult =
| Success of Number
| Failure of MathOperationError
and MathOperationError =
| DivideByZero
// services used by the calculator itself
type AccumulateNonZeroDigit = NonZeroDigit * DigitAccumulator -> DigitAccumulator
type AccumulateZero = DigitAccumulator -> DigitAccumulator
type AccumulateSeparator = DigitAccumulator -> DigitAccumulator
type DoMathOperation = CalculatorMathOp * Number * Number -> MathOperationResult
type GetNumberFromAccumulator = AccumulatorStateData -> Number
// services used by the UI or testing
type GetDisplayFromState = CalculatorState -> string
type GetPendingOpFromState = CalculatorState -> string
type CalculatorServices = {
accumulateNonZeroDigit :AccumulateNonZeroDigit
accumulateZero :AccumulateZero
accumulateSeparator :AccumulateSeparator
doMathOperation :DoMathOperation
getNumberFromAccumulator :GetNumberFromAccumulator
getDisplayFromState :GetDisplayFromState
getPendingOpFromState :GetPendingOpFromState
}
// ================================================
// Utilities
// ================================================
[<AutoOpen>]
module CommonComputationExpressions =
type MaybeBuilder() =
member this.Bind(x, f) = Option.bind f x
member this.Return(x) = Some x
let maybe = new MaybeBuilder()
// ================================================
// Implementation of Calculator
// ================================================
module CalculatorImplementation =
open CalculatorDomain
// helper to make defaultArg better for piping
let ifNone defaultValue input =
// just reverse the parameters!
defaultArg input defaultValue
let accumulateNonZeroDigit services digit accumulatorData =
let digits = accumulatorData.digits
let newDigits = services.accumulateNonZeroDigit (digit,digits)
let newAccumulatorData = {accumulatorData with digits=newDigits}
newAccumulatorData // return
let accumulateZero services accumulatorData =
let digits = accumulatorData.digits
let newDigits = services.accumulateZero digits
let newAccumulatorData = {accumulatorData with digits=newDigits}
newAccumulatorData // return
let accumulateSeparator services accumulatorData =
let digits = accumulatorData.digits
let newDigits = services.accumulateSeparator digits
let newAccumulatorData = {accumulatorData with digits=newDigits}
newAccumulatorData // return
let getComputationState services accumulatorStateData nextOp =
// helper to create a new ComputedState from a given displayNumber
// and the nextOp parameter
let getNewState displayNumber =
let newPendingOp =
nextOp |> Option.map (fun op -> op,displayNumber )
{displayNumber=displayNumber; pendingOp = newPendingOp }
|> ComputedState
let currentNumber =
services.getNumberFromAccumulator accumulatorStateData
// If there is no pending op, create a new ComputedState using the currentNumber
let computeStateWithNoPendingOp =
getNewState currentNumber
maybe {
let! (op,previousNumber) = accumulatorStateData.pendingOp
let result = services.doMathOperation(op,previousNumber,currentNumber)
let newState =
match result with
| Success resultNumber ->
// If there was a pending op, create a new ComputedState using the result
getNewState resultNumber
| Failure error ->
error |> ErrorState
return newState
} |> ifNone computeStateWithNoPendingOp
let replacePendingOp (computedStateData:ComputedStateData) nextOp =
let newPending = maybe {
let! existing,displayNumber = computedStateData.pendingOp
let! next = nextOp
return next,displayNumber
}
{computedStateData with pendingOp=newPending}
|> ComputedState
let handleZeroState services pendingOp input =
// create a new accumulatorStateData object that is used when transitioning to other states
let accumulatorStateData = {digits=""; pendingOp=pendingOp}
match input with
| Zero ->
ZeroState pendingOp // stay in ZeroState
| Digit digit ->
accumulatorStateData
|> accumulateNonZeroDigit services digit
|> AccumulatorState // transition to AccumulatorState
| DecimalSeparator ->
accumulatorStateData
|> accumulateSeparator services
|> AccumulatorWithDecimalState // transition to AccumulatorWithDecimalState
| MathOp op ->
let nextOp = Some op
let newState = getComputationState services accumulatorStateData nextOp
newState // transition to ComputedState or ErrorState
| Equals ->
let nextOp = None
let newState = getComputationState services accumulatorStateData nextOp
newState // transition to ComputedState or ErrorState
| Clear ->
ZeroState None // transition to ZeroState and throw away any pending ops
let handleAccumulatorState services stateData input =
match input with
| Zero ->
stateData
|> accumulateZero services
|> AccumulatorState // stay in AccumulatorState
| Digit digit ->
stateData
|> accumulateNonZeroDigit services digit
|> AccumulatorState // stay in AccumulatorState
| DecimalSeparator ->
stateData
|> accumulateSeparator services
|> AccumulatorWithDecimalState // transition to AccumulatorWithDecimalState
| MathOp op ->
let nextOp = Some op
let newState = getComputationState services stateData nextOp
newState // transition to ComputedState or ErrorState
| Equals ->
let nextOp = None
let newState = getComputationState services stateData nextOp
newState // transition to ComputedState or ErrorState
| Clear ->
ZeroState None // transition to ZeroState and throw away any pending ops
let handleAccumulatorWithDecimalState services stateData input =
match input with
| Zero ->
stateData
|> accumulateZero services
|> AccumulatorWithDecimalState // stay in AccumulatorWithDecimalState
| Digit digit ->
stateData
|> accumulateNonZeroDigit services digit
|> AccumulatorWithDecimalState // stay in AccumulatorWithDecimalState
| DecimalSeparator ->
//ignore
stateData
|> AccumulatorWithDecimalState // stay in AccumulatorWithDecimalState
| MathOp op ->
let nextOp = Some op
let newState = getComputationState services stateData nextOp
newState // transition to ComputedState or ErrorState
| Equals ->
let nextOp = None
let newState = getComputationState services stateData nextOp
newState // transition to ComputedState or ErrorState
| Clear ->
ZeroState None // transition to ZeroState and throw away any pending ops
let handleComputedState services stateData input =
let emptyAccumulatorStateData = {digits=""; pendingOp=stateData.pendingOp}
match input with
| Zero ->
ZeroState stateData.pendingOp // transition to ZeroState with any pending ops
| Digit digit ->
emptyAccumulatorStateData
|> accumulateNonZeroDigit services digit
|> AccumulatorState // transition to AccumulatorState
| DecimalSeparator ->
emptyAccumulatorStateData
|> accumulateSeparator services
|> AccumulatorWithDecimalState // transition to AccumulatorWithDecimalState
| MathOp op ->
// replace the pending op, if any
let nextOp = Some op
replacePendingOp stateData nextOp
| Equals ->
// replace the pending op, if any
let nextOp = None
replacePendingOp stateData nextOp
| Clear ->
ZeroState None // transition to ZeroState and throw away any pending ops
let handleErrorState stateData input =
match input with
| Zero
| Digit _
| DecimalSeparator
| MathOp _
| Equals ->
// stay in error state
ErrorState stateData
| Clear ->
ZeroState None // transition to ZeroState and throw away any pending ops
let createCalculate (services:CalculatorServices) :Calculate =
// create some local functions with partially applied services
let handleZeroState = handleZeroState services
let handleAccumulator = handleAccumulatorState services
let handleAccumulatorWithDecimal = handleAccumulatorWithDecimalState services
let handleComputed = handleComputedState services
let handleError = handleErrorState
fun (input,state) ->
match state with
| ZeroState stateData->
handleZeroState stateData input
| AccumulatorState stateData ->
handleAccumulator stateData input
| AccumulatorWithDecimalState stateData ->
handleAccumulatorWithDecimal stateData input
| ComputedState stateData ->
handleComputed stateData input
| ErrorState stateData ->
handleError stateData input
// ================================================
// Implementation of CalculatorConfiguration
// ================================================
module CalculatorConfiguration =
// A record to store configuration options
// (e.g. loaded from a file or environment)
type Configuration = {
decimalSeparator : string
divideByZeroMsg : string
maxDisplayLength: int
}
let loadConfig() = {
decimalSeparator =
System.Globalization.CultureInfo.CurrentCulture.NumberFormat.CurrencyDecimalSeparator
divideByZeroMsg = "ERR-DIV0"
maxDisplayLength = 10
}
// ================================================
// Implementation of CalculatorServices
// ================================================
module CalculatorServices =
open CalculatorDomain
open CalculatorConfiguration
let appendToAccumulator maxLen (accumulator:DigitAccumulator) appendCh =
// ignore new input if there are too many digits
if (accumulator.Length > maxLen) then
accumulator // ignore new input
else
// append the new char
accumulator + appendCh
let accumulateNonZeroDigit maxLen :AccumulateNonZeroDigit =
fun (digit, accumulator) ->
// determine what character should be appended to the display
let appendCh=
match digit with
| One -> "1"
| Two -> "2"
| Three-> "3"
| Four -> "4"
| Five -> "5"
| Six-> "6"
| Seven-> "7"
| Eight-> "8"
| Nine-> "9"
appendToAccumulator maxLen accumulator appendCh
let accumulateZero maxLen :AccumulateZero =
fun accumulator ->
let appendCh = "0"
appendToAccumulator maxLen accumulator "0"
let accumulateSeparator maxLen :AccumulateSeparator =
fun accumulator ->
let appendCh =
if accumulator = "" then "0." else "."
appendToAccumulator maxLen accumulator appendCh
let getNumberFromAccumulator :GetNumberFromAccumulator =
fun accumulatorStateData ->
let digits = accumulatorStateData.digits
match System.Double.TryParse digits with
| true, d -> d
| false, _ -> 0.0
let doMathOperation :DoMathOperation = fun (op,f1,f2) ->
match op with
| Add -> Success (f1 + f2)
| Subtract -> Success (f1 - f2)
| Multiply -> Success (f1 * f2)
| Divide ->
if f2 = 0.0 then
Failure DivideByZero
else
Success (f1 / f2)
let getDisplayFromState divideByZeroMsg :GetDisplayFromState =
// helper
let floatToString = sprintf "%g"
fun calculatorState ->
match calculatorState with
| ZeroState _ -> "0"
| AccumulatorState stateData
| AccumulatorWithDecimalState stateData ->
stateData
|> getNumberFromAccumulator
|> floatToString
| ComputedState stateData ->
stateData.displayNumber
|> floatToString
| ErrorState stateData ->
match stateData with
| DivideByZero -> divideByZeroMsg
let getPendingOpFromState :GetPendingOpFromState=
let opToString = function
| Add -> "+"
| Subtract -> "-"
| Multiply -> "*"
| Divide -> "/"
let displayStringForPendingOp pendingOp =
maybe {
let! op, number = pendingOp
return sprintf "%g %s" number (opToString op)
}
|> defaultArg <| ""
fun calculatorState ->
match calculatorState with
| ZeroState pendingOp ->
displayStringForPendingOp pendingOp
| AccumulatorState stateData
| AccumulatorWithDecimalState stateData ->
stateData.pendingOp
|> displayStringForPendingOp
| ComputedState stateData ->
stateData.pendingOp
|> displayStringForPendingOp
| ErrorState stateData ->
""
let createServices (config:Configuration) = {
accumulateNonZeroDigit = accumulateNonZeroDigit (config.maxDisplayLength)
accumulateZero = accumulateZero (config.maxDisplayLength)
accumulateSeparator = accumulateSeparator (config.maxDisplayLength)
doMathOperation = doMathOperation
getNumberFromAccumulator = getNumberFromAccumulator
getDisplayFromState = getDisplayFromState (config.divideByZeroMsg)
getPendingOpFromState = getPendingOpFromState
}
// ================================================
// Implementation of Calculator UI
// ================================================
module CalculatorUI =
open System
open System.Drawing
open System.Drawing.Drawing2D
open System.Windows.Forms
open CalculatorDomain
type CalculatorForm(initialState:CalculatorState, calculate:Calculate, getDisplay:GetDisplayFromState, getPendingOp:GetPendingOpFromState) as this =
inherit Form()
// constants
let margin = 20
let buttonDimension = 50
let buttonPadding = 10
let doubleDimension = buttonDimension + buttonPadding + buttonDimension
let gridSize = buttonDimension + buttonPadding
let buttonSize = Size(buttonDimension,buttonDimension)
let doubleWidthSize = Size(doubleDimension,buttonDimension)
let doubleHeightSize = Size(buttonDimension,doubleDimension)
let decimalSeparator = System.Globalization.CultureInfo.CurrentCulture.NumberFormat.CurrencyDecimalSeparator
let DigitButtonColor = Color.White
let OpButtonColor = Color.PeachPuff
let DangerButtonColor = Color.Coral
let largeFont = new Font(FontFamily.GenericSansSerif,14.f)
let smallFont = new Font(FontFamily.GenericSansSerif,9.f)
// initialization before constructor
let mutable state = initialState
// a function that sets the displayed text
let mutable setDisplayedText =
fun text -> () // do nothing
// traditional style -- have a label control as a field
// let mutable displayControl :Label = null
// a function that sets the pending op text
let mutable setPendingOpText =
fun text -> () // do nothing
// ========================
// private helper functions
// ========================
/// Get the physical location, given a row and column.
/// Row/col are 0-based
let getPos(row,col) =
let x = margin + (col*gridSize)
let y = margin + (row* gridSize)
Point(x,y)
let handleInput input =
let newState = calculate(input,state)
state <- newState
setDisplayedText (getDisplay state)
setPendingOpText (getPendingOp state)
// ========================
// initialization in constructor
// ========================
do
this.SetupForm()
// ========================
// Public methods
// ========================
/// Create a member rather than let-bound so it can be called from constructor
member this.SetupForm() =
this.Text <- "Calculator"
this.Font <- largeFont
let clientSizeX = (2*margin) + (5*buttonDimension) + (4*buttonPadding)
let clientSizeY = (2*margin) + (5*buttonDimension) + (4*buttonPadding)
this.ClientSize <- Size(clientSizeX,clientSizeY)
this.CenterToScreen()
let keyPressHandler = new KeyPressEventHandler(fun obj e -> this.KeyPressHandler(e))
this.KeyPress.AddHandler keyPressHandler
this.KeyPreview <- true // let the form handle keypress events
this.CreateButtons()
this.CreateDisplayLabel()
/// Use a member rather than a let-bound function so it can be called from the constructor
member this.CreateDisplayLabel() =
let pendingOpHeight = largeFont.Height
let displayWidth = 5*buttonDimension + 4*buttonPadding
// add a label to display the pending op
let pendingOpSize = Size(displayWidth,pendingOpHeight)
let pendingOpLocation = getPos(0,0)
let pendingOp = new Label(Text="",Size=pendingOpSize,Location=pendingOpLocation)
pendingOp.TextAlign <- ContentAlignment.BottomRight
pendingOp.BackColor <- Color.White
pendingOp.Font <- smallFont
this.Controls.Add(pendingOp)
setPendingOpText <-
(fun text -> pendingOp.Text <- text)
// add a label to display the current result
let displaySize = Size(displayWidth,buttonDimension - pendingOpHeight)
let displayLocation = getPos(0,0)
displayLocation.Offset(0,pendingOpHeight) // shift down below pending op label
let display = new Label(Text="",Size=displaySize,Location=displayLocation)
display.TextAlign <- ContentAlignment.MiddleRight
display.BackColor <- Color.White
this.Controls.Add(display)
// update the function that sets the text
setDisplayedText <-
(fun text -> display.Text <- text)
// traditional style - set the field when the form has been initialized
// displayControl <- display
/// Use a member rather than a let-bound function so it can be called from the constructor
member this.CreateButtons() =
let addButtonControl input (button:Button) =
button.Click.AddHandler(EventHandler(fun _ _ -> handleInput input))
this.Controls.Add(button)
let sevenButton = new Button(Text="7",Size=buttonSize,Location=getPos(1,0),BackColor=DigitButtonColor)
sevenButton |> addButtonControl (Digit Seven)
let eightButton = new Button(Text="8",Size=buttonSize,Location=getPos(1,1),BackColor=DigitButtonColor)
eightButton |> addButtonControl (Digit Eight)
let nineButton = new Button(Text="9",Size=buttonSize,Location=getPos(1,2),BackColor=DigitButtonColor)
nineButton |> addButtonControl (Digit Nine)
let clearButton = new Button(Text="C",Size=buttonSize,Location=getPos(1,3),BackColor=DangerButtonColor)
clearButton |> addButtonControl Clear
let addButton = new Button(Text="+",Size=doubleHeightSize,Location=getPos(1,4),BackColor=OpButtonColor)
addButton |> addButtonControl (MathOp Add)
let fourButton = new Button(Text="4",Size=buttonSize,Location=getPos(2,0),BackColor=DigitButtonColor)
fourButton |> addButtonControl (Digit Four)
let fiveButton = new Button(Text="5",Size=buttonSize,Location=getPos(2,1),BackColor=DigitButtonColor)
fiveButton |> addButtonControl (Digit Five)
let sixButton = new Button(Text="6",Size=buttonSize,Location=getPos(2,2),BackColor=DigitButtonColor)
sixButton |> addButtonControl (Digit Six)
let divideButton = new Button(Text="/",Size=buttonSize,Location=getPos(2,3),BackColor=OpButtonColor)
divideButton |> addButtonControl (MathOp Divide)
let oneButton = new Button(Text="1",Size=buttonSize,Location=getPos(3,0),BackColor=DigitButtonColor)
oneButton |> addButtonControl (Digit One)
let twoButton = new Button(Text="2",Size=buttonSize,Location=getPos(3,1),BackColor=DigitButtonColor)
twoButton |> addButtonControl (Digit Two)
let threeButton = new Button(Text="3",Size=buttonSize,Location=getPos(3,2),BackColor=DigitButtonColor)
threeButton |> addButtonControl (Digit Three)
let multButton = new Button(Text="*",Size=buttonSize,Location=getPos(3,3),BackColor=OpButtonColor)
multButton |> addButtonControl (MathOp Multiply)
let equalButton = new Button(Text="=",Size=doubleHeightSize,Location=getPos(3,4),BackColor=OpButtonColor)
equalButton |> addButtonControl Equals
let zeroButton = new Button(Text="0",Size=doubleWidthSize,Location=getPos(4,0),BackColor=DigitButtonColor)
zeroButton |> addButtonControl Zero
let pointButton = new Button(Text=decimalSeparator,Size=buttonSize,Location=getPos(4,2),BackColor=DigitButtonColor)
pointButton |> addButtonControl DecimalSeparator
let minusButton = new Button(Text="-",Size=buttonSize,Location=getPos(4,3),BackColor=OpButtonColor)
minusButton |> addButtonControl (MathOp Subtract)
member this.KeyPressHandler(e:KeyPressEventArgs) =
match e.KeyChar with
| '0' -> handleInput Zero
| '1' -> handleInput (Digit One)
| '2' -> handleInput (Digit Two)
| '3' -> handleInput (Digit Three)
| '4' -> handleInput (Digit Four)
| '5' -> handleInput (Digit Five)
| '6' -> handleInput (Digit Six)
| '7' -> handleInput (Digit Seven)
| '8' -> handleInput (Digit Eight)
| '9' -> handleInput (Digit Nine)
| '.' | ',' -> handleInput DecimalSeparator
| '+' -> handleInput (MathOp Add)
| '-' -> handleInput (MathOp Subtract)
| '/' -> handleInput (MathOp Divide)
| '*' -> handleInput (MathOp Multiply)
| '=' | '\n' | '\r' -> handleInput Equals
| 'C' | 'c' -> handleInput Clear
| _ -> ()
// ================================================
// Tests
// ================================================
module CalculatorTests =
open CalculatorDomain
open System
let config = CalculatorConfiguration.loadConfig()
let services = CalculatorServices.createServices config
let calculate = CalculatorImplementation.createCalculate services
let initialState = ZeroState None
/// Given a sequence of inputs, start with the empty state
/// and apply each input in turn. The final state is returned
let processInputs inputs =
// helper for fold
let folder state input =
calculate(input,state)
inputs
|> List.fold folder initialState
/// Check that the state contains the expected display value
let assertResult testLabel expected state =
let actual = services.getDisplayFromState state
if (expected <> actual) then
printfn "Test %s failed: expected=%s actual=%s" testLabel expected actual
else
printfn "Test %s passed" testLabel
let ``when I input 1, I expect 1``() =
[Digit One; ]
|> processInputs
|> assertResult "1" "1"
let ``when I input 1+, I expect 1``() =
[Digit One; MathOp Add]
|> processInputs
|> assertResult "1+" "1"
let ``when I input 1=, I expect 1``() =
[Digit One; Equals]
|> processInputs
|> assertResult "1=" "1"
let ``when I input 1+2, I expect 2``() =
[Digit One; MathOp Add; Digit Two]
|> processInputs
|> assertResult "1+2" "2"
let ``when I input 1+2=, I expect 3``() =
[Digit One; MathOp Add; Digit Two; Equals]
|> processInputs
|> assertResult "1+2=" "3"
let ``when I input 1+2+, I expect 3``() =
[Digit One; MathOp Add; Digit Two; MathOp Add; ]
|> processInputs
|> assertResult "1+2+" "3"
let ``when I input 1+2+4, I expect 4``() =
[Digit One; MathOp Add; Digit Two; MathOp Add; Digit Four]
|> processInputs
|> assertResult "1+2+4" "4"
let ``when I input 1+2+4=, I expect 7``() =
[Digit One; MathOp Add; Digit Two; MathOp Add; Digit Four; Equals]
|> processInputs
|> assertResult "1+2+4=" "7"
let ``when I input 4+-3=, I expect 1``() =
[Digit Four; MathOp Add; MathOp Subtract; Digit Three; Equals]
|> processInputs
|> assertResult "4+-3=" "1"
// run tests
do
``when I input 1, I expect 1``()
``when I input 1+, I expect 1``()
``when I input 1=, I expect 1``()
``when I input 1+2, I expect 2``()
``when I input 1+2=, I expect 3``()
``when I input 1+2+, I expect 3``()
``when I input 1+2+4, I expect 4``()
``when I input 1+2+4=, I expect 7``()
``when I input 4+-3=, I expect 1``()
// ================================================
// Bootstrapper
// ================================================
// assemble everything
open CalculatorDomain
open System
let config = CalculatorConfiguration.loadConfig()
let services = CalculatorServices.createServices config
let initialState = ZeroState None
let calculate = CalculatorImplementation.createCalculate services
let form = new CalculatorUI.CalculatorForm(initialState,calculate,services.getDisplayFromState,services.getPendingOpFromState)
form.Show()
(*
StateMachine.fsx
Related blog post: http://fsharpforfunandprofit.com/posts/calculator-complete-v2/
*)
module StateMachineExample =
type State =
| AState of AStateData
| BState of BStateData
| CState
and AStateData =
{something:int}
and BStateData =
{somethingElse:int}
type InputEvent =
| XEvent
| YEvent of YEventData
| ZEvent
and YEventData =
{eventData:string}
module StateMachineExampleImplemementation =
open StateMachineExample
(*
let transition (currentState,inputEvent) =
match currentState,inputEvent with
| AState, XEvent -> // new state
| AState, YEvent -> // new state
| AState, ZEvent -> // new state
| BState, XEvent -> // new state
| BState, YEvent -> // new state
| CState, XEvent -> // new state
| CState, ZEvent -> // new state
*)
(*
let aStateHandler stateData inputEvent =
match inputEvent with
| XEvent -> // new state
| YEvent _ -> // new state
| ZEvent -> // new state
let bStateHandler stateData inputEvent =
match inputEvent with
| XEvent -> // new state
| YEvent _ -> // new state
| ZEvent -> // new state
let cStateHandler inputEvent =
match inputEvent with
| XEvent -> // new state
| YEvent _ -> // new state
| ZEvent -> // new state
let transition (currentState,inputEvent) =
match currentState with
| AState stateData ->
// new state
aStateHandler stateData inputEvent
| BState stateData ->
// new state
bStateHandler stateData inputEvent
| CState ->
// new state
cStateHandler inputEvent
*)
let aStateHandler stateData inputEvent =
match inputEvent with
| XEvent ->
// transition to B state
BState {somethingElse=stateData.something}
| YEvent _ ->
// stay in A state
AState stateData
| ZEvent ->
// transition to C state
CState
let bStateHandler stateData inputEvent =
match inputEvent with
| XEvent ->
// stay in B state
BState stateData
| YEvent _ ->
// transition to C state
CState
let cStateHandler inputEvent =
match inputEvent with
| XEvent ->
// stay in C state
CState
| ZEvent ->
// transition to B state
BState {somethingElse=42}
let transition (currentState,inputEvent) =
match currentState with
| AState stateData ->
aStateHandler stateData inputEvent
| BState stateData ->
bStateHandler stateData inputEvent
| CState ->
cStateHandler inputEvent
// ========================================
// fixed up version that handles all events
module StateMachineExampleImplemementation_V2 =
open StateMachineExample
let aStateHandler stateData inputEvent =
match inputEvent with
| XEvent ->
// transition to B state
BState {somethingElse=stateData.something}
| YEvent _ ->
// stay in A state
AState stateData
| ZEvent ->
// transition to C state
CState
let bStateHandler stateData inputEvent =
match inputEvent with
| XEvent
| ZEvent ->
// stay in B state
BState stateData
| YEvent _ ->
// transition to C state
CState
let cStateHandler inputEvent =
match inputEvent with
| XEvent
| YEvent _ ->
// stay in C state
CState
| ZEvent ->
// transition to B state
BState {somethingElse=42}
let transition (currentState,inputEvent) =
match currentState with
| AState stateData ->
aStateHandler stateData inputEvent
| BState stateData ->
bStateHandler stateData inputEvent
| CState ->
cStateHandler inputEvent
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