static Value Parse(Scanner scan)
{
var tk = scan.Next();
if (tk.Item1 == TokenType.Word)
return new Word(tk.Item2);
else if (tk.Item1 == TokenType.Nil)
return List.Nil;
else if (tk.Item1 == TokenType.True)
return True.T;
else if (tk.Item1 == TokenType.Number)
return new Int(int.Parse(tk.Item2));
else if (tk.Item1 == TokenType.String)
return new String(tk.Item2);
else if (tk.Item1 == TokenType.LParen)
{
var cons = new Stack<Value>();
while ((tk = scan.Peek()).Item1 != TokenType.RParen && tk.Item1 != TokenType.EOF)
{
cons.Push(Parse(scan));
}
if (tk.Item1 != TokenType.RParen)
throw new Exception("Missing RParen.");
scan.Next();
List ret = List.Nil;
while (cons.Count != 0)
{
ret = new List(cons.Pop(), ret);
}
return ret;
}
else if (tk.Item1 == TokenType.Quote)
return new Quote(Parse(scan));
else if (tk.Item1 == TokenType.RParen)
throw new Exception("Unexpected RParen.");
else
throw new Exception("Unknown token type.");
}
static void Eval(this Environment env, string code)
{
var scan = new Scanner(new StringReader(code));
var val = Parse(scan);
val.Eval(env);
}
static void Main()
{
var top = new Environment();
AddBuiltinFunctions(top);
AddExtraFunctions(top);
Console.Write("> ");
var scan = new Scanner(Console.In);
while (scan.Peek().Item1 != TokenType.EOF)
{
try
{
Console.WriteLine(Parse(scan).Eval(top));
}
catch (Exception ex)
{
Console.WriteLine(" Error: {0}", ex.Message);
}
Console.Write("> ");
}
}
static void AddBuiltinFunctions(Environment top)
{
//Missing: cond, atom
top.Add("+", new BuiltinFunction((env, args) =>
{
int accum = 0;
while (args != List.Nil)
{
accum += ((Int)args.Val.Eval(env)).Val;
args = args.Next;
}
return new Int(accum);
}));
top.Add("list", new BuiltinFunction((env, args) =>
{
return args.Map(v => v.Eval(env));
}));
top.Add("cons", new BuiltinFunction((env, args) =>
{
return new List(args.Val.Eval(env), (List)args.Next.Val.Eval(env));
}));
top.Add("quote", new BuiltinFunction((env, args) =>
{
return args.Val;
}));
top.Add("car", new BuiltinFunction((env, args) =>
{
var l = args.Val.Eval(env) as List;
return l.Val;
}));
top.Add("cdr", new BuiltinFunction((env, args) =>
{
var l = args.Val.Eval(env) as List;
return l.Next;
}));
top.Add("print", new BuiltinFunction((env, args) =>
{
Value v = args.Val.Eval(env);
string str;
if (v is String)
str = ((String)v).Val;
else
str = v.ToString();
Console.WriteLine(str);
return List.Nil;
}));
top.Add("if", new BuiltinFunction((env, args) =>
{
if (args.Val.Eval(env).IsTrue())
return args.Next.Val.Eval(env);
else
return args.Next.Next.Val.Eval(env);
}));
top.Add("listp", new BuiltinFunction((env, args) =>
{
if (args.Val.Eval(env) is List)
return True.T;
else
return List.Nil;
}));
top.Add("lambda", new BuiltinFunction((env, args) =>
{
var formalArgs = ((List)args.Val);
var body = args.Next.Map(v => v.Eval(env));
var newFun = new UserFunction(formalArgs, body);
return newFun;
}));
top.Add("defmacro", new BuiltinFunction((env, args) =>
{
var name = ((Word)args.Val).Val;
var formalArgs = ((List)args.Next.Val);
var body = (List)args.Next.Next.Val;
var newFun = new UserMacro(formalArgs, body);
top[name] = newFun;
return newFun;
}));
top.Add("exit", new BuiltinFunction((env, args) =>
{
var exitArg = args.Val.Eval(env) as Int;
int exitCode = 0;
if (exitArg != null)
exitCode = exitArg.Val;
System.Environment.Exit(exitCode);
return List.Nil;
}));
top.Add("eq", new BuiltinFunction((env, args) =>
{
var v1 = args.Val.Eval(env);
var v2 = args.Next.Val.Eval(env);
if (v1.Equals(v2))
return True.T;
else
return List.Nil;
}));
top.Add("code", new BuiltinFunction((env, args) =>
{
var val = args.Val.Eval(env);
if (val is UserFunction)
{
var fun = args.Val.Eval(env) as UserFunction;
return new List(fun.mArgNames, new List(fun.mFun, List.Nil));
}
else if (val is UserMacro)
{
var fun = args.Val.Eval(env) as UserMacro;
return new List(fun.mArgNames, new List(fun.mFun, List.Nil));
}
else
throw new Exception("Could not find user function.");
}));
top.Add("read", new BuiltinFunction((env, args) =>
{
var fileName = ((String)args.Val.Eval(env)).Val;
var values = new Stack<Value>();
using (var file = new StreamReader(fileName))
{
var scan = new Scanner(file);
while (scan.Peek().Item1 != TokenType.EOF)
{
values.Push(Parse(scan));
}
}
var ret = List.Nil;
foreach (var v in values)
{
ret = new List(v, ret);
}
return ret;
}));
top.Add("eval", new BuiltinFunction((env, args) =>
{
return args.Val.Eval(env).Eval(env);
}));
top.Add("env", new BuiltinFunction((env, args) =>
{
return env.AsList();
}));
top.Add("let", new BuiltinFunction((env, args) =>
{
var name = (Word)args.Val;
var val = args.Next.Val.Eval(env);
top[name.Val] = val;
return val;
}));
top.Add("save", new BuiltinFunction((env, args) =>
{
var fileName = ((String)args.Val.Eval(env)).Val;
var stuff = args.Next.Val.Eval(env);
File.WriteAllText(fileName, stuff.ToString());
return stuff;
}));
top.Add("new", new BuiltinFunction((env, args) =>
{
string className;
var nameValue = args.Val.Eval(env);
if (nameValue is String)
className = ((String)nameValue).Val;
else if (nameValue is Word)
className = ((Word)nameValue).Val;
else
throw new Exception(nameValue.ToDotNetValue() + " is not a valid class name.");
Type type = Type.GetType(className);
if (type == null)
{
foreach (var a in SearchAssemblies)
{
type = a.GetType(className);
if (type != null)
break;
}
}
if (type == null)
throw new Exception("Could not find type '" + className + "'.");
return new DotNetValue(Activator.CreateInstance(type));
}));
}