/// <summary>
/// Parses an infix expression into a an RPN token queue.
/// </summary>
/// <param name="expression">The expression to parse.</param>
/// <returns>An RPN token queue.</returns>
public ExpressionQueue Parse(string expression)
{
ExpressionQueue output = new ExpressionQueue(expression);
Stack <Token> stack = new Stack <Token>();
if (!string.IsNullOrEmpty(expression))
{
int i = 0;
ReadResult result;
while (i < expression.Length)
{
result = this.ReadOperand(expression, i);
if (result.Success)
{
output.Enqueue(result.Token);
i = result.Position;
}
else
{
result = this.ReadOperator(expression, i);
if (result.Success)
{
RaspyOperator op1 = (RaspyOperator)result.Token;
while (stack.Count > 0 && stack.Peek().IsOperator)
{
RaspyOperator op2 = (RaspyOperator)stack.Peek();
if ((op1.Associativity == Associativity.Left && op1.Precedence <= op2.Precedence) ||
(op1.Associativity == Associativity.Right && op1.Precedence < op2.Precedence))
{
output.Enqueue(stack.Pop());
}
else
{
break;
}
}
stack.Push(result.Token);
i = result.Position;
}
else if (expression[i] == '(')
{
stack.Push(new Parenthesis(ParenthesisType.Left));
i++;
}
else if (expression[i] == ')')
{
bool foundLeft = false;
while (stack.Count > 0)
{
Token token = stack.Peek();
if (token.IsOperator)
{
output.Enqueue(stack.Pop());
}
else if (token.IsParenthesis)
{
if (((Parenthesis)token).ParenthesisType == ParenthesisType.Left)
{
stack.Pop();
foundLeft = true;
break;
}
}
}
i++;
if (!foundLeft)
{
throw new RaspyParseException("The expression contains mismatched parentheses.", expression);
}
}
else if (!char.IsWhiteSpace(expression[i]))
{
throw new RaspyParseException(string.Format(CultureInfo.InvariantCulture, "The expression contains an invalid character, '{0}'.", expression[i]), expression);
}
else
{
i++;
}
}
}
while (stack.Count > 0)
{
Token token = stack.Peek();
if (!token.IsParenthesis)
{
output.Enqueue(stack.Pop());
}
else
{
throw new RaspyParseException("The expression contains mismatched parentheses.", expression);
}
}
}
return(output);
}
/// <summary>
/// Evaluates a parsed arithmetic expression.
/// </summary>
/// <param name="expression">The expression to evaluate.</param>
/// <returns>The result of the evaluation.</returns>
public object Evaluate(ExpressionQueue expression)
{
if (expression == null)
{
throw new ArgumentNullException("expression", "expression cannot be null.");
}
string infixExpression = expression.InfixExpression;
string parsedExpression = expression.ToString();
Stack <Token> stack = new Stack <Token>();
try
{
while (expression.Count > 0)
{
Token token = expression.Dequeue();
if (token.IsOperator)
{
RaspyOperator op = (RaspyOperator)token;
IOperationProvider provider = this.providerFactory.GetProvider(op.Symbol);
if (provider != null)
{
List <Token> args = new List <Token>();
int i = op.ArgumentCount;
while (i-- > 0)
{
args.Add(stack.Pop());
}
args.Reverse();
stack.Push(provider.Operate(op, args.ToArray()));
}
else
{
throw new RaspyEvaluationException(
string.Format(CultureInfo.InvariantCulture, "No provider could be found for operator '{0}'.", op.Symbol),
infixExpression,
parsedExpression);
}
}
else
{
stack.Push(token);
}
}
if (stack.Count != 1 || !stack.Peek().IsOperand)
{
throw new RaspyEvaluationException(
string.Format(CultureInfo.InvariantCulture, "Invalid expression: '{0}'.", parsedExpression),
infixExpression,
parsedExpression);
}
return(((Operand)stack.Pop()).Value);
}
catch (RaspyException)
{
throw;
}
catch (Exception ex)
{
throw new RaspyEvaluationException(
string.Format(CultureInfo.InvariantCulture, "An error occurred while evaluating the expression '{0}'.", parsedExpression),
ex,
infixExpression,
parsedExpression);
}
}