free 2d barcode generator asp.net I LANGUAGE-ORIENTED PROGRAMMING in Font

Generator Data Matrix 2d barcode in Font I LANGUAGE-ORIENTED PROGRAMMING

type LineDetails = { pen : Pen definition : LineDefinition } let f32 x = Float32.of_float x let f64 x = Float.of_float32 x type Graph = class inherit Control val mutable maxX : float val mutable maxY : float val mutable minX : float val mutable minY : float val mutable lines : LineDetails list new () as x = { maxX = 1.0; maxY = 1.0; minX = -1.0; minY = -1.0; lines = [] } then x.Paint.Add(fun e -> x.DrawGraph(e.Graphics)) x.Resize.Add(fun _ -> x.Invalidate()) member f.DrawGraph(graphics : Graphics) = let height = Convert.ToSingle(f.Height) let width = Convert.ToSingle(f.Width) let widthF = f32 f.maxY - f32 f.minY let heightF = f32 f.maxX - f32 f.minX let stepY = height / heightF let stepX = width / widthF let orginY = (0.0f - f32 f.minY) * stepY let orginX = (0.0f - f32 f.minX) * stepX let black = new Pen(Color.Black) graphics.DrawLine(black, 0.0f, orginY, width, orginY) graphics.DrawLine(black, orginX, 0.0f, orginX, height) let mapPoint pt = new PointF(orginX + (f32 pt.X * stepX), height - (orginY + (f32 pt.Y * stepY)))

let xs = { f.minX .. (1.0 / f64 stepX) .. f.maxX } f.lines |> List.iter (fun line -> LineFunctions.sample xs line.definition |> Seq.map mapPoint |> Seq.to_array |> (fun pts -> graphics.DrawLines(line.pen, pts))) end module GraphTest = begin let let let let wiggle = PointList [ (0.1,0.6); (0.3,-0.3); (0.5,0.8); (0.7,-0.2) ] straight = Function (fun x -> x + 0.1) square = Function (fun x -> x * x) strange = Combination [ (0.2, square); (0.4, wiggle); (0.4, straight) ]

let lines = [{ pen = new Pen(Color.Blue) ; definition = wiggle }; { pen = new Pen(Color.Orange, DashStyle = DashStyle.Dot, Width = 2.0f) ; definition = straight }; { pen = new Pen(Color.Red, DashStyle = DashStyle.Dash, Width = 2.0f) ; definition = square }; { pen = new Pen(Color.Green, Width = 2.0f) ; definition = strange } ] let form = let temp = new Form(Visible=true,TopMost=true) let g = new Graph(Dock = DockStyle.Fill) g.lines <- lines temp.Controls.Add(g) temp [<STAThread>] do Application.Run(form) end This example produces the graph in Figure 11-1.

In 6 you used quotations; these are quoted sections of F# code where the quote operator instructs the compiler to generate data structures representing the code rather than IL representing the code. This means instead of code that can be executed, you have a data structure that represents the code that was coded, and you re free to do what you want with it. You can either interpret it, performing the actions you require as you go along, or compile it into another language. Or you can simply ignore it if you want. You could, for example, take a section of quoted code and compile it for another runtime, such as the Java virtual machine (JVM). Or, like the LINQ example in 9, you could turn it into SQL and execute it against a database. In the next example, you ll write an interpreter for integer-based arithmetic expressions in F#. This might be useful for learning how stack-based calculations work. Here, your language is already designed for you; it is the syntax available in F#. You ll work exclusively with arithmetic expressions of the form (2 * (2 - 1)) / 2 . This means you need to generate an error whenever you come across syntax that is neither an integer nor an operation. When working with quotations, you have to query the expression that you receive to see whether it is a specific type of expression. For example, here you query an expression to see whether it is an integer, and if it is, you push it onto the stack: match uexp with | Raw.Int32(x) -> printf "Push: %i\r\n" x operandsStack.Push(x) | _ ->