Phil Trelford's Array
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February 16, 2011 02:53 by phil

Cellz is an Open Source functional .Net Silverlight Spreadsheet application written in F# and published on CodePlex.

It is part inspired by the last chapter of Martin Odersky’s excellent Programming in Scala book where he develops a simple Spreadsheet implementation in a couple of hundred lines. As per Scala, F# can excel when building a Spreadsheet app too. Parser combinators can be used to parse formulas and .Net events to propagate changes back to dependent cells. Silverlight’s built-in DataGrid control can be used for displaying and editing a sheet:

The grid supports decimal and string literals, cell references as well as formulas with operators and functions e.g.

  • Hello World
  • 1234.5
  • = 1 + 1
  • = A1
  • = SUM(A1:E1)

Techie bit


The View type binds a DataGrid to a sheet of cells using different templates for viewing and editing modes:

type View(sheet:Sheet) as view = 
    inherit UserControl()
    let grid = DataGrid(AutoGenerateColumns=false,
    do  grid.LoadingRow.Add (fun e ->
            let row = e.Row.DataContext :?> Row
            e.Row.Header <- row.Index
    do  view.Content <- grid
    let createColumn i =
        let header = colIndex.toColName i
        let col = DataGridTemplateColumn(Header=header,
        let path = sprintf "Cells.[%d]" i
        col.CellTemplate <- 
            sprintf "<TextBlock Text='{Binding %s.Value}'/>" path 
            |> toDataTemplate
        col.CellEditingTemplate <- 
            sprintf "<TextBox Text='{Binding %s.Data,Mode=TwoWay}'/>" path
            |> toDataTemplate
    do  for i = 0 to sheet.ColumnCount-1 do createColumn i |> grid.Columns.Add
    do  grid.ItemsSource <- sheet.Rows

The sheet type simply exposes rows of cells:

type Sheet (colCount,rowCount) as sheet =
    let rows =  
        [|for i = 0 to rowCount-1 do 
            let cells = [|for i=0 to colCount-1 do yield Cell()|]
            yield Row(RowIndex(i),cells)|]
    member sheet.Rows = rows

The cell type exposes a Data property for the formula while editing and a Value property for display:

type Cell () as cell =
    inherit ObservableObject()
    let mutable expr = expr.empty
    let mutable formula = ""
    let mutable value = value.empty
    let updated = Event<_>()
    let update newValue generation =
        value <- newValue
        cell.NotifyPropertyChanged <@ cell.Value @>
        updated.Trigger generation
    let eval () =
        try expr.Evaluate() with
        e -> String "N/A"
    member cell.Data
        with get () = formula
        and set value =
            formula <- value
            expr <- try parse value 
                    with e -> Value(String "N/A")
            cell.NotifyPropertyChanged <@ cell.Data @>
            let newValue = eval ()
            update newValue 0
    member cell.Value
        with get () = value
        and set newValue = update newValue 0

All the source code is available on CodePlex.


Categories: .Net | F# | Silverlight
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February 16. 2011 17:13


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February 25. 2011 12:25


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F# Discoveries This Week 02/25/2011 «  F# Central

April 3. 2011 17:33

Paul Cechner

Hey man, I've decided to take the plunge and libraries like this really help beginners like me on the way.

Keep up the good work bro

Paul Cechner

April 3. 2011 17:36

Paul Cechner

(now you just have to convince Jon to offer up a free beginners version of his visualisation libraries)

Paul Cechner

August 30. 2012 00:25


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