September 2010 Help Wanted

[Charles]

Cobra is an open source project under the MIT license and relies on contributions from volunteers. If you would like to contribute, here are some areas where we need help:

-- Implement treaps in Cobra. These would be another kind of collection beyond list, dictionary and set. There is at least a Python library for this.

Sample Programs/Libraries

These could be in any area:

-- games
-- web sites
-- business apps
-- science
-- number crunching
-- finance
-- gui
-- utility
-- class library to help in some area


Cobra Server Work

Port phpBB to something Trac-based so phpBB can be retired and the server software simplified. I think there is at least one Trac plug-in for discussions, but when I looked at it a couple years ago it was lacking some basic features.

Port svn+trac to hg+trac. This would empower us to have more branches and forks.

Feel free to add to this list.


Back ends

-- Mac/ObjC back-end

-- JVM back-end


IDEs

-- IDE support for Visual Studio or MonoDevelop or SharpDevelop or Continuum


If you need help getting started on anything, feel free to ask here in the forums, typically with a new discussion post with a specific subject.

[gradha]

Are you thinking of providing Cobra with something like Python's "batteries included"?

[Charles]

Python's "batteries included" refers to the standard library being quite capable. Cobra has had this from the beginning (including other features like machine code generation) through the virtual machines--.NET and Mono.

But your question reminds me of another item:

-- Implement a How To or write a wiki page on using .NET sockets in Cobra.

Thanks.

[Charles]

Bump.

[hopscc]

A Treaps implementation in cobra provided in ticket:263.

Includes tests, test/sample and a speed comparison check (slower than Dict and Lists, Faster than SortedDict).

Possibly needs augmenting/modifying to be in the Cobra.Lang namespace and to advertise implementing IDictionary<of TKey, TValue> interface (?)

[Charles]

Thanks. I'll take a look sometime soon. Putting it on a ticket is nice as I'm working through them.

[ArturMustafin]

I can try to implement my latest sources of C# generic grammar-driven LL(1) (optionally amibigous, non-LL(1) or/and non-LR(1) grammar) table non-recursive (optionally descent recursive) parser to cobra language, as mixed-mode language sample. I recently simplified a lot my library for use of generics and interfaces. So i need some replaceable parts as HashSet<T>, Dictionary<T> and List<T> as generic first-class BCL classes in Cobra.

at http://expressionscompiler.codeplex.com/SourceControl/list/changesets

Sample expression grammar:

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E ← T | T Eopt
T ← F | F Topt
F ← N | '(' E ')'
N ← '0' | '1'
Eopt ← '+' E | '-' E
Topt ← '*' T | '/' T


Complete C# parser definition:

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        private Entity CreateGrammar()
        {
            Terminal[] _ = { '0', '1', '(', ')', '+', '-', '*', '/' };

            Nonterminal G = "G";
            Nonterminal E = "E";
            Nonterminal Eopt = "E'";

            Nonterminal T = "T";
            Nonterminal Topt = "T'";

            Nonterminal F = "F";
            Nonterminal N = "N";

            G.Definition = new Rules
            {
                () => E[false] + Terminal.Null
            };

            E.Definition = new Rules
            {
                () => T[false] + Eopt[true]
            };

            T.Definition = new Rules
            {
                () => F[false] + Topt[true]
            };

            F.Definition = new Rules
            {
                () => N[false],
                () => '(' + E[false] + ')'
            };

            N.Definition = new Rules
            {
                () => '0',
                () => '1'
            };

            Eopt.Definition = new Rules
            {
                () => '+' + E[false],
                () => '-' + E[false]
            };

            Topt.Definition = new Rules
            {
                () => '*' + T[false],
                () => '/' + T[false]
            };

            G.Initialize();
            G.Validate();

            return G;
        }


Sample code for AST tree evaluation can be found in source code download.

[Charles]

Some quick notes:

-- We already have List<of T> and Dictionary<of T>. Note the use of "of"

-- Instead of "HashSet", just say "Set" as in "Set<of T>"

-- We have a wiki page with tips on porting from C#.

-- Lambda expressions in Cobra start with "do" as in "do=a+b" or "do(i as int)=i*2"

HTH

[_Alex_]

Here is a simple example of OpenGL code using OpenTK library:

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use System
use System.Diagnostics
use System.Drawing
use System.IO
use OpenTK
use OpenTK.Graphics
use OpenTK.Graphics.OpenGL

class HelloGL3 inherits GameWindow
   var vertexShaderHandle as int
   var fragmentShaderHandle as int
   var shaderProgramHandle as int
   var modelviewMatrixLocation as int
   var projectionMatrixLocation as int
   var vaoHandle as int
   var positionVboHandle as int
   var normalVboHandle as int
   var eboHandle as int
   var vertexShaderSource as String = '\n#version 130\n\nprecision highp float;\n\nuniform mat4 projection_matrix;\nuniform mat4 modelview_matrix;\n\nin vec3 in_position;\nin vec3 in_normal;\n\nout vec3 normal;\n\nvoid main(void)\n{\n  //works only for orthogonal modelview\n  normal = (modelview_matrix * vec4(in_normal, 0)).xyz;\n  \n  gl_Position = projection_matrix * modelview_matrix * vec4(in_position, 1);\n}\n\t'
   var fragmentShaderSource as String = '\n#version 130\n\nprecision highp float;\n\nconst vec3 ambient = vec3(0.1, 0.1, 0.1);\nconst vec3 lightVecNormalized = normalize(vec3(0.5, 0.5, 2.0));\nconst vec3 lightColor = vec3(0.9, 0.9, 0.7);\n\nin vec3 normal;\n\nout vec4 out_frag_color;\n\nvoid main(void)\n{\n  float diffuse = clamp(dot(lightVecNormalized, normalize(normal)), 0.0, 1.0);\n  out_frag_color = vec4(ambient + diffuse * lightColor, 1.0);\n}\t\n\t'
   var positionVboData as Vector3[] = @[Vector3(-1.0 to float32, -1.0  to float32,  1.0 to float32), Vector3( 1.0 to float32, -1.0 to float32,  1.0 to float32), Vector3( 1.0 to float32,  1.0 to float32,  1.0 to float32), Vector3(-1.0 to float32,  1.0 to float32,  1.0 to float32), Vector3(-1.0 to float32, -1.0 to float32, -1.0 to float32), Vector3( 1.0 to float32, -1.0 to float32, -1.0 to float32), Vector3( 1.0 to float32,  1.0 to float32, -1.0 to float32), Vector3(-1.0 to float32,  1.0 to float32, -1.0 to float32) ]
   var indicesVboData as int[] = @[ 0, 1, 2, 2, 3, 0,  3, 2, 6, 6, 7, 3,  7, 6, 5, 5, 4, 7,  4, 0, 3, 3, 7, 4,  0, 1, 5, 5, 4, 0,  1, 5, 6, 6, 2, 1, ]
      # // front face
      # 0, 1, 2, 2, 3, 0,
      # // top face
      # 3, 2, 6, 6, 7, 3,
      # // back face
      # 7, 6, 5, 5, 4, 7,
      # // left face
      # 4, 0, 3, 3, 7, 4,
      # // bottom face
      # 0, 1, 5, 5, 4, 0,
      # // right face
      # 1, 5, 6, 6, 2, 1,
      # ]

   var projectionMatrix as Matrix4
   var modelviewMatrix as Matrix4

   cue init
      base.init(
         640 , 480 ,
         GraphicsMode(),
         "OpenGL 3 Example",
         0 to OpenTK.GameWindowFlags, DisplayDevice.default,
         3, 0, GraphicsContextFlags.ForwardCompatible | GraphicsContextFlags.Debug
         )
   
   def onLoad(e as System.EventArgs?) is override,protected
      .vSync = VSyncMode.On
      .createShaders
      .createVBOs
      .createVAOs
      # // Other state
      GL.enable(EnableCap.DepthTest)
      GL.clearColor(System.Drawing.Color.midnightBlue)

   def createShaders # is override,protected
      .vertexShaderHandle = GL.createShader(ShaderType.VertexShader)
      .fragmentShaderHandle = GL.createShader(ShaderType.FragmentShader)

      GL.shaderSource(.vertexShaderHandle, .vertexShaderSource)
      GL.shaderSource(.fragmentShaderHandle, .fragmentShaderSource)

      GL.compileShader(.vertexShaderHandle)
      GL.compileShader(.fragmentShaderHandle)

      Debug.writeLine(GL.getShaderInfoLog(.vertexShaderHandle))
      Debug.writeLine(GL.getShaderInfoLog(.fragmentShaderHandle))

      # Create program
      .shaderProgramHandle = GL.createProgram

      GL.attachShader(.shaderProgramHandle, .vertexShaderHandle)
      GL.attachShader(.shaderProgramHandle, .fragmentShaderHandle)

      GL.linkProgram(.shaderProgramHandle)

      Debug.writeLine(GL.getProgramInfoLog(.shaderProgramHandle))

      GL.useProgram(.shaderProgramHandle)
      
      # Set uniforms
      .projectionMatrixLocation = GL.getUniformLocation(.shaderProgramHandle, "projection_matrix")
      .modelviewMatrixLocation =  GL.getUniformLocation(.shaderProgramHandle, "modelview_matrix")

      aspectRatio as float = .clientSize.width / (.clientSize.height to float)
      Matrix4.createPerspectiveFieldOfView((Math.pi / 4) to float32, aspectRatio to float32, 1 to float32, 100 to float32, out .projectionMatrix)
      .modelviewMatrix = Matrix4.lookAt(Vector3(0, 3, 5), Vector3(0, 0, 0), Vector3(0, 1, 0))

      GL.uniformMatrix4(.projectionMatrixLocation, false , inout .projectionMatrix)
      GL.uniformMatrix4(.modelviewMatrixLocation , false , inout .modelviewMatrix)

   def createVBOs # is override,protected
      GL.genBuffers(1, out .positionVboHandle)
      GL.bindBuffer(BufferTarget.ArrayBuffer, .positionVboHandle)
      GL.bufferData<of Vector3>(
         BufferTarget.ArrayBuffer,
         IntPtr(.positionVboData.length * Vector3.sizeInBytes),
         .positionVboData,
         BufferUsageHint.StaticDraw
         )

      GL.genBuffers(1, out .normalVboHandle)
      GL.bindBuffer(BufferTarget.ArrayBuffer, .normalVboHandle)
      GL.bufferData<of Vector3>(
         BufferTarget.ArrayBuffer,
         IntPtr(.positionVboData.length * Vector3.sizeInBytes),
         .positionVboData,
         BufferUsageHint.StaticDraw
         )

      GL.genBuffers(1, out .eboHandle)
      GL.bindBuffer(BufferTarget.ElementArrayBuffer, .eboHandle)
      GL.bufferData(
         BufferTarget.ElementArrayBuffer,
         IntPtr(Cobra.Lang.NumericTypeInfo(uint).size * .indicesVboData.length),
         .indicesVboData,
         BufferUsageHint.StaticDraw
         )

      GL.bindBuffer(BufferTarget.ArrayBuffer, 0)
      GL.bindBuffer(BufferTarget.ElementArrayBuffer, 0)

   def createVAOs # is override,protected
      # GL3 allows us to store the vertex layout in a "vertex array object" (VAO).
      # This means we do not have to re-issue VertexAttribPointer calls
      # every time we try to use a different vertex layout - these calls are
      # stored in the VAO so we simply need to bind the correct VAO.
      GL.genVertexArrays(1, out .vaoHandle)
      GL.bindVertexArray(.vaoHandle)

      GL.enableVertexAttribArray(0)
      GL.bindBuffer(BufferTarget.ArrayBuffer, .positionVboHandle)
      GL.vertexAttribPointer(0, 3, VertexAttribPointerType.Float, true, Vector3.sizeInBytes, 0)
      GL.bindAttribLocation(.shaderProgramHandle, 0, "in_position")

      GL.enableVertexAttribArray(1)
      GL.bindBuffer(BufferTarget.ArrayBuffer, .normalVboHandle)
      GL.vertexAttribPointer(1, 3, VertexAttribPointerType.Float, true, Vector3.sizeInBytes, 0)
      GL.bindAttribLocation(.shaderProgramHandle, 1, "in_normal")

      GL.bindBuffer(BufferTarget.ElementArrayBuffer, .eboHandle)

      GL.bindVertexArray(0)

   def onUpdateFrame(e as FrameEventArgs?) is override,protected
      rotation as Matrix4 = Matrix4.createRotationY(e.time to float32)
      Matrix4.mult(inout rotation, inout .modelviewMatrix, out .modelviewMatrix)
      GL.uniformMatrix4(.modelviewMatrixLocation, false, inout .modelviewMatrix)

      if .keyboard[OpenTK.Input.Key.Escape]
         .exit

   def onRenderFrame(e as FrameEventArgs?) is override,protected
      GL.viewport(0, 0, .width, .height)
      
      GL.clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit)

      GL.bindVertexArray(.vaoHandle)
      GL.drawElements(BeginMode.Triangles, .indicesVboData.length,
         DrawElementsType.UnsignedInt, IntPtr.zero)

      .swapBuffers


class Program
   def main has STAThread
      example = HelloGL3()
      # Utilities.SetWindowTitle(example)
      # example.run(30)
      example.run
      # Application.run(MyForm())



Notice how ugly is vertexShaderSource that is not multiline string. I didn`t realize that only docstrings can be multiline. For now I am using python to do

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print repr(""" ... shader code ... """)

then copypasta that into source.

Also if I erase brackets from

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example = HelloGL3()

to get

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example = HelloGL3

I get compiler error

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error: Cannot find a definition for "run" in "example" whose type is "Type".

Does this mean that brackets are needed to indicate object instantination or else class object would be assigned ?