private static Expression ParseExp(TokenStream tokenStream, SymbolTable symbols)
{
var head = ParseTerm(tokenStream, symbols);
while (true)
{
if (tokenStream.Done() || tokenStream.Peek() == ')')
return head;
var next = ParseTerm(tokenStream, symbols);
head = new Apply(head, next);
}
}
public static string Evaluate(string text)
{
var tokenStream = new TokenStream(text);
Expression exp = ParseExp(tokenStream, new SymbolTable());
if (!tokenStream.Done())
throw new ParserException(String.Format("Extra characters after position {0}", tokenStream.Position));
var resolved = exp.Reduce();
if (resolved == null)
return "";
return resolved.ToString();
}