static public object Initial(SCode expression, Environment environment)
{
object answer;
Thread.CurrentThread.Priority = ThreadPriority.AboveNormal;
#if DEBUG
Timer tosProbe = new Timer(SCode.TopOfStackProbe, null, 5, 3);
SCode.topOfStackTimer = tosProbe;
#endif
Control residual = expression.PartialEval(PartialEnvironment.Make((ITopLevelEnvironment)environment)).Residual;
while (true)
{
answer = null;
while (residual.EvalStep(out answer, ref residual, ref environment))
{
}
;
if (answer == Interpreter.UnwindStack)
{
// What are we doing here? Someone unwound the stack!
// There are three possibilities to consider:
// 1) A cwcc has just performed a destructive read of the stack.
// In this case, we convert the newly captured frame list
// into a control point and reload it.
//
// 2) A within-continuation has blown away the stack in order
// to install a different control point. In this case we
// reload the control point that was stored in the UnwinderState.
//
// 3) The stack was unwound in order to exit the interpreter.
// In this case, we return from the initial continuation.
if (((UnwinderState)environment).IsExit)
{
answer = ((UnwinderState)environment).ExitValue;
break;
}
else
{
ControlPoint stateToRestore = ((UnwinderState)environment).ToControlPoint();
// the receiver gets control when the stack is put back.
Control receiver = ((UnwinderState)environment).Receiver;
// the rewind state goes in the closureEnvironment
environment = new RewindState(stateToRestore, receiver);
// Start reloading by returning control to the lowest
// frame.
residual = ((RewindState)environment).PopFrame();
}
}
}
Debug.WriteLine("Interpreter exited with value " + answer.ToString());
return(answer);
}
public static bool ScodeEval(out object answer, object arg0, object arg1)
{
Environment env = Environment.ToEnvironment(arg1);
//CompileTimeEnvironment ctenv = (env is StandardEnvironment)
// ? new CompileTimeEnvironment (((StandardEnvironment) env).Closure.Lambda.Formals)
// : new CompileTimeEnvironment (null);
SCode sarg0 = SCode.EnsureSCode(arg0);
answer = new TailCallInterpreter(sarg0.PartialEval(PartialEnvironment.Make((ITopLevelEnvironment)env)).Residual, env);
return(true);
}
