feat (exm): van der pol example

src/bin/main.ml

@@ -9,9 +9,15 @@ let stop    = ref 30.0
 let greedy  = ref false
 let inplace = ref false
 let steps   = ref 1
+let model   = ref ""
 
 let gt0i v i = v := if i <= 0   then 1   else i
 let gt0f v f = v := if f <= 0.0 then 1.0 else f
+let hasmodel = ref false
+
+let set_model s =
+  if !hasmodel then raise (Arg.Bad "Too many arguments.") else
+  model := s; hasmodel := true
 
 let opts = [
   "-sample",  Arg.Int (gt0i sample), "n \tSample count (default=10)";
@@ -22,16 +28,19 @@ let opts = [
   "-steps",   Arg.Int (gt0i steps),  "n \tSplit into [n] steps (default=1)";
 ]
 
-let errmsg = "Usage: " ^ Sys.executable_name ^ " [OPTIONS]\nOptions are:"
+let errmsg = "Usage: " ^ Sys.executable_name ^ " [OPTIONS] MODEL\nOptions are:"
 
-let () = try Arg.parse (Arg.align opts) (fun _ -> ()) errmsg with _ -> exit 2
+let () = try Arg.parse (Arg.align opts) set_model errmsg with _ -> exit 2
 
 let output = Output.print !sample
 
 let c = StatefulRK45.(if !inplace then InPlace.csolve else Functional.csolve)
 let z = StatefulZ.(Functional.zsolve)
 let s = Solver.solver_c c z
-let m = Ball.bouncing_ball ()
+let m = match !model with
+  | "ball" -> Ball.bouncing_ball ()
+  | "vdp"  -> Vdp.van_der_pol ()
+  | _      -> raise (Arg.Bad (Format.sprintf "Unknown model: %s." !model))
 
 let state = if !inplace then (module State.InPlaceSimState    : State.SimState)
                         else (module State.FunctionalSimState : State.SimState)