static public Expression Parse(object a)
{
if (a is Symbol)
{
if (((Symbol)a).val.IndexOf(".") == -1)
{
return(new Var(a as Symbol));
}
else
{
string aString = ((Symbol)a).val;
int posLastDot = aString.LastIndexOf(".");
Expression[] rands = new Expression[2];
rands[0] = Expression.Parse(Symbol.Create(aString.Substring(0, posLastDot)));
rands[1] = new Lit(Symbol.Create(aString.Substring(posLastDot + 1, aString.Length - posLastDot - 1)));
return(new App(Expression.Parse(Symbol.Create("get-property")), rands));
}
}
if (a is Pair)
{
Pair pair = a as Pair;
object car = pair.car;
switch (car.ToString())
{
case "begin":
Expression[] exps = new Expression[pair.cdr.Count];
int pos = 0;
foreach (object obj in pair.cdr)
{
exps[pos] = Parse(obj);
// exps[pos].Mark(obj);
pos++;
}
Begin beginExps = new Begin(exps);
// beginExps.Mark(pair);
return(beginExps);
case "if":
Pair curr = pair.cdr;
Expression test_exp = Parse(curr.car);
// test_exp.Mark(curr.car);
curr = curr.cdr;
Expression true_exp = Parse(curr.car);
// true_exp.Mark(curr.car);
curr = curr.cdr;
Expression false_exp = Parse(curr.car);
// false_exp.Mark(curr.car);
return(new If(test_exp, true_exp, false_exp));
case "quote":
return(new Lit(pair.cdr.car));
case "set!":
{
Symbol var = pair.cdr.car as Symbol;
if (var == null)
{
throw new Exception("set! error -> variable must be a symbol: " + Util.Dump(pair));
}
Expression exp = Parse(pair.cdr.cdr.car) as Expression;
// exp.Mark(pair.cdr.cdr.car);
if (var.val.IndexOf('.') == -1)
{
Assignment assignment = new Assignment(var, exp);
// assignment.Mark(pair);
return(assignment);
}
else
{
string aString = var.val;
int posLastDot = aString.LastIndexOf(".");
Expression[] rands = new Expression[3];
rands[0] = Expression.Parse(Symbol.Create(aString.Substring(0, posLastDot)));
rands[1] = new Lit(Symbol.Create(aString.Substring(posLastDot + 1, aString.Length - posLastDot - 1)));
rands[2] = exp;
App app = new App(Expression.Parse(Symbol.Create("set-property")), rands);
// app.Mark(pair);
return(app);
}
}
case "lambda":
// Debug.WriteLine("sparsing lambda " + pair.ToString());
curr = pair.cdr as Pair;
Symbol[] ids = null;
bool all_in_one = false;
if (curr.car != null)
{
if (curr.car is Pair)
{
Object[] ids_as_obj = (curr.car as Pair).ToArray();
ids = new Symbol[ids_as_obj.Length];
for (int i = 0; i < ids_as_obj.Length; i++)
{
ids[i] = ids_as_obj[i] as Symbol;
if (ids[i] == null)
{
throw new Exception("lambda error -> params must be symbols: " + Util.Dump(pair));
}
}
}
else
{
all_in_one = true;
ids = new Symbol[1];
ids[0] = curr.car as Symbol;
if (ids[0] == null)
{
throw new Exception("lambda error -> params must be symbols: " + Util.Dump(pair));
}
}
}
curr = curr.cdr as Pair;
// insert implied begin if neccessary
Expression body;
if (curr.cdr == null)
{
body = Parse(curr.car);
// if (curr.car is Pair)
// body.Mark(curr.car);
// else
// body.Mark(curr);
}
else
{
Expression[] begin = new Expression[curr.Count];
pos = 0;
foreach (object obj in curr)
{
begin[pos] = Parse(obj);
// begin[pos].Mark(obj);
pos++;
}
body = new Begin(begin);
}
return(new Proc(ids, body, all_in_one));
default: // app
if (pair.hasMember)
{
Expression[] rands = new Expression[2];
if (pair.member.IndexOf('.') != -1)
{
string currentMember = pair.member;
int posLastDot = currentMember.LastIndexOf(".");
pair.member = currentMember.Substring(0, posLastDot);
rands[0] = Expression.Parse(pair);
pair.member = currentMember;
rands[1] = new Lit(Symbol.Create(currentMember.Substring(posLastDot + 1, currentMember.Length - posLastDot - 1)));
}
else
{
pair.hasMember = false;
rands[0] = Expression.Parse(pair);
pair.hasMember = true;
rands[1] = new Lit(Symbol.Create(pair.member));
}
return(new App(Expression.Parse(Symbol.Create("get-property")), rands));
}
else
{
Expression[] rands = null;
if (pair.cdr != null)
{
rands = new Expression[pair.cdr.Count];
pos = 0;
foreach (object obj in pair.cdr)
{
rands[pos] = Expression.Parse(obj);
// rands[pos].Mark(obj);
pos++;
}
}
IPrim prim = Primitives.getPrim(pair.car.ToString());
if (prim != null)
{
Primapp primapp = new Primapp(prim, rands);
// primapp.Mark(pair);
return(primapp);
}
else
{
App app = new App(Expression.Parse(pair.car), rands);
// app.Mark(pair);
return(app);
}
}
}
}
else
{
return(new Lit(a));
}
}
public object Eval(TextReader str)
{
//Console.WriteLine("starting eval");
Object evaledObj = null;
Object parsedObj = Util.read(str);
if (parsedObj is Pair)
{
if (macros.Count > 0)
{
// bool curRunHidden = DebugInfo.RunHidden;
// DebugInfo.RunHidden = true; //don't debug the macro expension code
Closure macroExpand = initEnv.Apply(Symbol.Create("macro-expand")) as Closure;
parsedObj = macroExpand.Eval(new Object[] { parsedObj });
// DebugInfo.RunHidden = curRunHidden;
}
Pair p = parsedObj as Pair;
switch (p.car.ToString())
{
case "define":
Expression expr = null;
Symbol def = null;
if (p.cdr.car is Pair) // (define (fn x y) body)
{
Pair def_and_args = p.cdr.car as Pair;
Pair body = p.cdr.cdr;
Pair syms = def_and_args.cdr;
def = Symbol.Create(def_and_args.car.ToString());
expr = Expression.Parse(Pair.Cons(Symbol.Create("lambda"), Pair.Cons(syms, body)));
// Debug.WriteLine(def + "-->" + expr);
}
else // (define fn (lambda (x y) body))
{
def = Symbol.Create(p.cdr.car.ToString());
expr = Expression.Parse(p.cdr.cdr.car);
}
//initEnv = new Extended_Env(new Pair(def), new Pair(null), initEnv);
//Object value = Eval(expr);
//Console.WriteLine("defining: " + def);
// expr.Mark(p);
initEnv.Bind(def, Eval(expr));
break;
case "macro":
Symbol name = p.cdr.car as Symbol;
// Console.WriteLine("macrodef" + name + " " + Expression.Parse(p.cdr.cdr.car).Eval(initEnv).ToString());
Closure transformer = (Closure)Expression.Parse(p.cdr.cdr.car).Eval(initEnv);
this.macros[name] = transformer;
// Console.WriteLine("macro: " + name);
break;
default:
// need to call macro-expand in here. but how?
evaledObj = Util.Dump(Eval(Expression.Parse(parsedObj)));
break;
}
}
else
{
evaledObj = Util.Dump(Eval(Expression.Parse(parsedObj)));
}
if (str.Peek() == -1)
{
return(evaledObj);
}
else
{
return(Eval(str));
}
}