private Expr parse(string input)
{
string in_ = eatWhitespace(input);
if (peekChar(in_) == '(')
{
in_ = eatWhitespace(eatChar('(', in_));
Expr fun;
List <Expr> args = new List <Expr>();
string fun_string;
if (peekChar(in_) == '(')
{
fun_string = peekList(in_);
fun = parse(fun_string);
}
else
{
fun_string = peekWord(in_);
if (env.ContainsKey(fun_string))
{
fun = new VarExpr(fun_string);
}
else
{
switch (fun_string)
{
case "lambda":
return(parseLam(in_));
case "define":
return(parseDef(in_));
case "if": // if appears to be special too
return(parseIf(in_));
case "or":
return(parseOr(in_));
case "and":
return(parseAnd(in_));
default:
{
fun = new VarExpr(fun_string);
break;
}
}
}
}
in_ = eatWhitespace(eatWord(fun_string, in_));
while (peekChar(in_) != ')')
{
if (peekChar(in_) == '(')
{
string word = peekList(in_);
args.Add(parse(word));
in_ = eatWhitespace(eatWord(word, in_));
}
else
{
string word = peekWord(in_);
args.Add(parse(word));
in_ = eatWhitespace(eatWord(word, in_));
}
}
return(new AppExpr(fun, args, env));
}
else
{
if (peekChar(in_) == '"') // we have a string
{
return(new StrExpr(in_));
}
long num;
if (Int64.TryParse(input, out num))
{
return(new NumExpr(num));
}
else if (input == "empty")
{
return(new EmptyExpr());
}
else if (input == "#t" || input == "true")
{
return(new BoolExpr(true));
}
else if (input == "#f" || input == "false")
{
return(new BoolExpr(false));
}
else
{
return(new VarExpr(input));
}
}
}
private Expr parse(string input)
{
string in_ = eatWhitespace(input);
if (peekChar(in_) == '(')
{
in_ = eatWhitespace(eatChar('(', in_));
Expr fun;
List<Expr> args = new List<Expr>();
string fun_string;
if (peekChar(in_) == '(')
{
fun_string = peekList(in_);
fun = parse(fun_string);
}
else
{
fun_string = peekWord(in_);
if (env.ContainsKey(fun_string))
fun = new VarExpr(fun_string);
else
switch (fun_string)
{
case "lambda":
return parseLam(in_);
case "define":
return parseDef(in_);
case "if": // if appears to be special too
return parseIf(in_);
case "or":
return parseOr(in_);
case "and":
return parseAnd(in_);
default:
{
fun = new VarExpr(fun_string);
break;
}
}
}
in_ = eatWhitespace(eatWord(fun_string, in_));
while (peekChar(in_) != ')')
{
if (peekChar(in_) == '(')
{
string word = peekList(in_);
args.Add(parse(word));
in_ = eatWhitespace(eatWord(word, in_));
}
else
{
string word = peekWord(in_);
args.Add(parse(word));
in_ = eatWhitespace(eatWord(word, in_));
}
}
return new AppExpr(fun, args, env);
}
else
{
if (peekChar(in_) == '"') // we have a string
return new StrExpr(in_);
long num;
if (Int64.TryParse(input, out num))
{
return new NumExpr(num);
}
else if (input == "empty")
return new EmptyExpr();
else if (input == "#t" || input == "true")
return new BoolExpr(true);
else if (input == "#f" || input == "false")
return new BoolExpr(false);
else
return new VarExpr(input);
}
}