F# version of tipcalculator.cs example for Continuous app

tip.fsx

//
// Tip Calculator Example
//
// Calculates a tip and total given a bill amount
//

open System;
open Xamarin.Forms;

let clr1 = Color.FromRgb (150, 200, 190)
let mutable tipperc = 20.0

let title = Label (
    Text = "Tip Calculator",
    FontSize = 16.0,
    FontFamily = "Zapfino",
    HorizontalOptions = LayoutOptions.Center,
    Margin = Thickness(0.0, 64.0, 0.0, 0.0)
)

let billEntry = Entry (
    Text = "12.43",
    FontSize = 32.0,
    Placeholder = (0.0).ToString("C"),
    HeightRequest = 44.0,
    HorizontalTextAlignment = TextAlignment.Center,
    Margin = Thickness(50.0, 0.0, 50.0, 0.0)
)

let percent = Picker (
    Title = "%",
    HorizontalOptions = LayoutOptions.Center
    //VerticalOptions = LayoutOptions.CenterAndExpand
)

let perc = [10.0; 15.0; 18.0; 20.0; 25.0; 30.0]

let addit v =
    match v with
    | [] -> ()
    | x::xs -> percent.Items.Add x.ToString()
              addit xs
              
addit perc

let tip = Label (
    Text = "Tip",
    FontSize = 28.0,
    HorizontalOptions = LayoutOptions.Center
)
  
let total = Label (
    Text = "Total",
    FontSize = 28.0,
    HorizontalOptions = LayoutOptions.Center
)


let UpdateOutput () = 
    let valtext = billEntry.Text
    //printfn valtext
    let mutable value = Double.Parse (billEntry.Text)

    let tipval = Math.Round (value * tipperc) / 100.0
    tip.Text <- "Tip " + tipval.ToString "C"
    let tt = value + tipval
    total.Text <- "Total " + tt.ToString "C"

billEntry.TextChanged.Add ( fun (a : TextChangedEventArgs ) ->
    UpdateOutput ()
)

UpdateOutput ()

percent.SelectedIndexChanged.Add (fun (a : EventArgs) ->
    tipperc <- match percent.SelectedIndex with
    | -1 -> 20.0
    | _ -> perc.Item percent.SelectedIndex
    UpdateOutput ()
)
    
percent.SelectedIndex <- 3

let pageStack = StackLayout()
let outs = StackLayout (
    Margin = Thickness(50.0, 0.0, 50.0, 0.0)
)

outs.Children.Add tip
outs.Children.Add total

outs.BackgroundColor <- clr1.WithLuminosity 0.8
pageStack.Children.Add title
pageStack.Children.Add billEntry
pageStack.Children.Add percent
pageStack.Children.Add outs
pageStack.BackgroundColor <- clr1

let Main = ContentPage (
    Content = pageStack
)