/// <summary>
/// 二元计算
/// </summary>
/// <param name="left"></param>
/// <param name="right"></param>
/// <param name="op"></param>
/// <returns></returns>
public object DyadicOperation(ExpNode left, ExpNode right, string symbol)
{
IOperator iOp = OperatorFactory.GetOperator(symbol);
iOp.LeftOperand = OperandOperation(left).ToString();
iOp.RightOperand = OperandOperation(right).ToString();
return(iOp.Eval());
// return iOp.Eval(;
}
/// <summary>
/// Algo of EvaluateRPN (source : Expression Evaluator : using RPN by lallous
/// in the C++/MFC section of www.CodeProject.com.
/// 1. Initialize stack for storing results, prepare input postfix (or RPN) expression.
/// 2. Start scanning from left to right till we reach end of RPN expression
/// 3. Get token, if token is:
/// I. An operator:
/// a. Get top of stack and store into variable op2; Pop the stack
/// b. Get top of stack and store into variable op1; Pop the stack
/// c. Do the operation expression in operator on both op1 and op2
/// d. Push the result into the stack
/// II. An operand: stack its numerical representation into our numerical stack.
/// 4. At the end of the RPN expression, the stack should only have one value and
/// that should be the result and can be retrieved from the top of the stack.
/// </summary>
/// <param name=szExpr>Expression to be evaluated in RPNotation with
/// single character variables</param>
/// <param name=htValues>Values for each of the variables in the expression</param>
///
public object EvaluateRPN(ArrayList arrExpr, Type varType, Hashtable htValues)
{
// initialize stack (integer stack) for results
Stack stPad = new Stack();
// begin loop : scan from left to right till end of RPN expression
foreach (object var in arrExpr)
{
Operand op1 = null;
Operand op2 = null;
IOperator oprtr = null;
// Get token
// if token is
if (var is IOperand)
{
// Operand : push onto top of numerical stack
stPad.Push(var);
}
else if (var is IOperator)
{
// Operator :
// Pop top of stack into var 1 - op2 first as top of stack is rhs
op2 = (Operand)stPad.Pop();
if (htValues != null)
{
op2.Value = htValues[op2.Name];
}
// Pop top of stack into var 2
op1 = (Operand)stPad.Pop();
if (htValues != null)
{
op1.Value = htValues[op1.Name];
}
// Do operation exp for 'this' operator on var1 and var2
oprtr = (IOperator)var;
IOperand opRes = oprtr.Eval(op1, op2);
// Push results onto stack
stPad.Push(opRes);
}
}
// end loop
// stack ends up with single value with final result
return(((Operand)stPad.Pop()).Value);
}
/// <summary>
/// Evalua una expresion dada en notacion postfijo.
/// </summary>
/// <param name="postfixExp">Expresion en postfijo a evaluar.</param>
/// <returns>El valor resultante de la evaluacion.</returns>
private string EvaluatePostfix(string postfixExp)
{
Stack <Operand> operandStack = new Stack <Operand>();
string[] tokenArray = postfixExp.Split(' ');
foreach (string pretoken in tokenArray)
{
Tokenizer token = new Tokenizer(pretoken);
IEnumerator <Token> enumerator = token.GetTokens().GetEnumerator();
while (enumerator.MoveNext())
{
Token item = enumerator.Current;
switch (item.Type)
{
case TokenType.True:
operandStack.Push(new Operand(true));
break;
case TokenType.False:
operandStack.Push(new Operand(false));
break;
case TokenType.Constant:
operandStack.Push(new Operand(int.Parse(item.Value)));
break;
case TokenType.Minus:
if (enumerator.MoveNext() && enumerator.Current.Type != TokenType.Minus)
{
operandStack.Push(new Operand(int.Parse(enumerator.Current.Value) * -1));
}
else
{
goto case TokenType.Plus;
}
break;
case TokenType.Plus:
case TokenType.Asterisk:
case TokenType.Slash:
case TokenType.Percent:
case TokenType.Ampersand:
case TokenType.Caret:
case TokenType.Greater:
case TokenType.GreaterEqual:
case TokenType.Less:
case TokenType.LessEqual:
case TokenType.Equal:
case TokenType.NotEqual:
try
{
IOperator oper = Operations[item.Value];
Operand op2 = operandStack.Pop();
Operand op1 = operandStack.Pop();
operandStack.Push(oper.Eval(op1, op2));
}
catch (InvalidCastException e)
{
throw new InvalidOperationException("Incorrect expression.", e);
}
break;
default:
throw new InvalidOperationException("Incorrect input expression.");
}
}
}
if (operandStack.Count == 1)
{
string result = operandStack.Pop().Value.ToString();
return(result);
}
else
{
throw new Exception("Unknown error.");
}
}
