Editing OCaml (section)

===Triangle (graphics)===
The following program renders a rotating triangle in 2D using [[OpenGL]]:

<syntaxhighlight lang="OCaml">
let () =
  ignore (Glut.init Sys.argv);
  Glut.initDisplayMode ~double_buffer:true ();
  ignore (Glut.createWindow ~title:"OpenGL Demo");
  let angle t = 10. *. t *. t in
  let render () =
    GlClear.clear [ `color ];
    GlMat.load_identity ();
    GlMat.rotate ~angle: (angle (Sys.time ())) ~z:1. ();
    GlDraw.begins `triangles;
    List.iter GlDraw.vertex2 [-1., -1.; 0., 1.; 1., -1.];
    GlDraw.ends ();
    Glut.swapBuffers () in
  GlMat.mode `modelview;
  Glut.displayFunc ~cb:render;
  Glut.idleFunc ~cb:(Some Glut.postRedisplay);
  Glut.mainLoop ()
</syntaxhighlight>

The LablGL bindings to OpenGL are required. The program may then be compiled to bytecode with:

 $ ocamlc -I +lablGL lablglut.cma lablgl.cma simple.ml -o simple

or to nativecode with:

 $ ocamlopt -I +lablGL lablglut.cmxa lablgl.cmxa simple.ml -o simple

or, more simply, using the ocamlfind build command
 $ ocamlfind opt simple.ml -package lablgl.glut -linkpkg -o simple

and run:

 $ ./simple

Far more sophisticated, high-performance 2D and 3D graphical programs can be developed in OCaml. Thanks to the use of OpenGL and OCaml, the resulting programs can be cross-platform, compiling without any changes on many major platforms.