private void ProcessOperator(StringScanner steve, Stack<string> opStack, List<Token> output,
bool lastTokenWasNumber, ref bool tokenIsNumber)
{
string op = steve.Read ().ToString();
if (lastTokenWasNumber) {
PushOperatorToStack (op, opStack, output);
} else if (op.Equals ("-")) {
// The last token wasn't a number, but we encountered an operator, so this must be a negative sign
steve.skipWhitespace ();
if (!steve.HasNext ()) {
throw new InvalidExpressionException("misplaced operator: " + op);
}
BigInteger num = 1;
// if there's an expression after the minus sign, just process it and negate it
if (steve.TryReadLong (ref num) || Char.ToLower (steve.Peek ()) == 'd' || steve.Peek() == '(' || steve.Peek() == '[') {
output.Add (new NumToken(-num));
// if the next token is a diedef, paren, or formula, iterativelyAdd will detect the -1 and use it to negate the expression
tokenIsNumber = true;
} else {
// there is no number after the minus sign, so it can't be negating a number, and it can't be doing subtraction
throw new InvalidExpressionException ("misplaced operator: " + op);
}
} else {
throw new InvalidExpressionException ("misplaced operator" + op);
}
}
private Token ProcessDieDef(
StringScanner steve,
Stack<string> opStack,
List<Token> output,
bool lastTokenWasNumber)
{
steve.TrySkip(); // move past the d\
if (!steve.HasNext())
throw new InvalidExpressionException("no die type given");
if (Char.IsDigit (steve.Peek ())) { // check that the syntax is valid before just trying to read it
Token dieCount = new NumToken(1);
if (lastTokenWasNumber) {
// the last number was the die count, because it was followed by a 'd'
dieCount = output.Last();
output.RemoveAt (output.Count - 1);
}
BigInteger dieType = steve.ReadLong(); // this is safe because we checked that the next char is a digit
// we now know that die type and the die count, now we need to see if there are extra instructions for the roll
long keepCount = 1;
KeepStrategy keepstrat = KeepStrategy.ALL;
if (steve.HasNext () && char.IsLetter (steve.Peek ()) && Char.ToLower (steve.Peek ()) != 'd') {
char extension = Char.ToLower (steve.Read ());
if (extension == 'h') {
keepstrat = KeepStrategy.HIGHEST;
BigInteger temp = null;
if (steve.TryReadLong (ref temp)) {
if (temp > MAX_DIECOUNT) {
throw new InvalidExpressionException (temp.ToString () + " is too many dice");
} else {
keepCount = temp.LongValue ();
}
}
} else if (extension == 'l') {
keepstrat = KeepStrategy.LOWEST;
BigInteger temp = null;
if (steve.TryReadLong (ref temp)) {
if (temp > MAX_DIECOUNT) {
throw new InvalidExpressionException (temp.ToString () + " is too many dice");
} else {
keepCount = temp.LongValue ();
}
}
} else {
throw new InvalidExpressionException("invalid die extension " + extension);
}
}
var countList = new List<Token> ();
countList.Add (dieCount);
return new DiceToken (countList, dieType, keepCount, keepstrat, this);
} else {
throw new InvalidExpressionException("no die type given");
}
}
// computes and returns the value of an expression in parentheses.
// The scanner cursor should be pointing at the opening paren when this is called.
// When this method returns, the scanner cursor will be pointing at the character directly after the closing paren.
// Returns the expression in parentheses
private string ExtractParentheses(StringScanner scanner)
{
StringBuilder steve = new StringBuilder ();
int nestCount = 1; // track nested parentheses
scanner.TrySkip (); // move past open-paren
if (!scanner.HasNext ())
throw new InvalidExpressionException ("mismatched parentheses");
while (!(scanner.Peek () == ')' && nestCount == 1)) {
if (scanner.Peek () == '(') {
nestCount++;
} else if (scanner.Peek () == ')') {
nestCount--;
}
steve.Append (scanner.Read ());
if (!scanner.HasNext ())
throw new InvalidExpressionException ("mismatched parentheses");
}
scanner.Read (); // move past close-paren
DebugMessage ("evaluating \"" + steve.ToString () + "\" in parentheses");
return steve.ToString ();
}
// converts an infix dice formula to a postfix list of tokens. Can return throw InvalidExpressionException if the expression is invalid.
private List<Token> InfixToPostfix(string input, int index, string formulaName)
{
if (formulaName != null) {
// we are evaluating a formula, and will push it to the formulaNest so that we can prevent self-referential formulas
Assert(!formulaNest.Contains (formulaName), "[" + formulaName + "] is self-referential");
formulaNest.Push(formulaName);
}
StringScanner steve = new StringScanner (input, index);
Stack<string> operatorStack = new Stack<string> ();
List<Token> output = new List<Token>();
steve.skipWhitespace ();
bool lastTokenWasNumber = false;
while (steve.HasNext()) {
bool tokenIsNumber = false;
if (Char.ToLower (steve.Peek ()) == 'd') {
output.Add (ProcessDieDef (steve, operatorStack, output, lastTokenWasNumber));
tokenIsNumber = true;
} else if (IsCharOperator (steve.Peek ())) {
ProcessOperator (steve, operatorStack, output, lastTokenWasNumber, ref tokenIsNumber);
} else if (Char.IsDigit (steve.Peek ())) {
output.Add (new NumToken(steve.ReadLong ()));
tokenIsNumber = true;
} else if (steve.Peek () == '(') {
ProcessParentheses(steve, output, lastTokenWasNumber);
tokenIsNumber = true;
} else if (steve.Peek() == '[') {
ProcessFormula(steve, output, lastTokenWasNumber);
tokenIsNumber = true;
} else if (steve.Peek () == ')') {
// processParentheses reads all the valid close-parens, so if we find one here it must be mismatched
throw new InvalidExpressionException ("mismatched parentheses");
} else {
throw new InvalidExpressionException("invalid symbol: " + steve.Peek());
}
steve.skipWhitespace ();
lastTokenWasNumber = tokenIsNumber;
}
while (operatorStack.Count > 0) {
Assert (operatorStack.Peek () == "(", "mismatched parentheses");
output.Add(OpToken.Get(operatorStack.Pop ()));
}
if (formulaName != null) {
formulaNest.Pop ();
}
return output;
}
// reads the name of a formula, evaluates its expression, and returns the result.
// the scanner cursor should be pointing at the opening bracket when this is called.
// When this method returns, the cursor will be pointing at the character after the closing bracket.
private Formula ExtractFormula(StringScanner scanner)
{
StringBuilder steve = new StringBuilder ();
scanner.TrySkip();
if (!scanner.HasNext ())
throw new InvalidExpressionException ("mismatched brackets");
while (scanner.Peek () != ']') {
steve.Append (scanner.Read ());
if (!scanner.HasNext ())
throw new InvalidExpressionException ("mismatched brackets");
}
scanner.Read ();
Formula f = formulas [steve.ToString ()];
if (f == null)
throw new InvalidExpressionException ("No formula " + steve.ToString ());
return f;
}