F# Geometry types

rectangle.fs

type Rect =
  { Left:int; Top:int; Width:int; Height:int }
  with
    static member create(w, h) = { Left=0; Top=0; Width=w; Height=h }
    static member create(l,t,r,b) = { Left=l; Top=t; Width=(r-l)+1; Height=(b-t)+1 }
    static member shrink n r = { Left=r.Left+n; Top=r.Top+n; Width=r.Width-2*n; Height=r.Height-2*n }
    static member scan r =
      seq {
        for y = r.Top to r.Top+r.Height-1 do
          for x = r.Left to r.Left+r.Width-1 do
            yield x,y
      }