/// <summary>
/// 将表达式中的操作数和运算符分割出来
/// </summary>
/// <param name="expression">文本表达式</param>
/// <returns>操作数与运算符表</returns>
internal static List <IOperatorOrOperand> SplitExpression(string expression)
{
List <IOperatorOrOperand> output = new List <IOperatorOrOperand>();
StringBuilder operandbuf = new StringBuilder();
StringBuilder operatorbuf = new StringBuilder();
// 记录刚才最后输出的表达式项
IOperatorOrOperand lastItem = null;
// 在尾部添加一个空格，帮助分离最后一个操作数或运算符
expression = expression + " ";
double result = 0;
for (int i = 0; i < expression.Length; i++)
{
if (char.IsDigit(expression[i]) == true || expression[i] == '.')
{
// 如果是数字或小数点（操作数成份）
// 结束前一个运算符
if (operatorbuf.Length > 0)
{
// 尝试获取运算符
OperatorBase opr = TryGetOperator(operatorbuf.ToString(), lastItem);
if (opr != null)
{
output.Add(opr);
lastItem = opr;
operatorbuf.Length = 0;
}
else
{
throw new InvalidCastException(operatorbuf.ToString() + " 无法解析为合法的运算符。");
}
}
// 合并入当前操作数项
operandbuf.Append(expression[i]);
}
else
{
// 不是数字或小数点（运算符成份）
// 结束前一个操作数
if (operandbuf.Length > 0)
{
if (double.TryParse(operandbuf.ToString(), out result) == false)
{
throw new FormatException(operandbuf.ToString() + " 无法解析为合法的操作数。");
}
// 输出操作数
OperandInfo operand = new OperandInfo(double.Parse(operandbuf.ToString()));
output.Add(operand);
lastItem = operand;
operandbuf.Length = 0;
}
// 合并非空白字符到当前运算符项
if (char.IsWhiteSpace(expression[i]) == false)
{
operatorbuf.Append(expression[i]);
}
// 分析并输出运算符
if (operatorbuf.Length > 0)
{
// 尝试获取运算符
OperatorBase opr = TryGetOperator(operatorbuf.ToString(), lastItem);
if (opr != null)
{
output.Add(opr);
lastItem = opr;
operatorbuf.Length = 0;
}
}
}
}
return(output);
}
/// <summary>
/// 尝试返回一个运算符对象
/// </summary>
/// <param name="exp">要测试的字符串</param>
/// <param name="leftItem"></param>
/// <returns>如果成功，返回一个运算符对象实例；否则返回空</returns>
private static OperatorBase TryGetOperator(string exp, IOperatorOrOperand leftItem)
{
// 判断左侧是否是操作数
bool hasLeftOperand = false;
if (leftItem == null)
{
// 没有左项
hasLeftOperand = false;
}
else if (leftItem.IsOperand)
{
// 左项是操作数
hasLeftOperand = true;
}
else if (leftItem.GetType() == typeof(OperatorCloseBracket))
{
// 左项是闭括号
hasLeftOperand = true;
}
else
{
// 其它情况
hasLeftOperand = false;
}
// 根据符号文本判断
string symbol = exp.ToUpper();
switch (symbol)
{
case "(":
return(new OperatorOpenBracket());
case ")":
return(new OperatorCloseBracket());
}
// 根据左操作数情况判断
if (hasLeftOperand == true)
{
// 有左操作数者
switch (exp.ToUpper())
{
case "+":
return(new OperatorPlus());
case "-":
return(new OperatorMinus());
case "*":
return(new OperatorMultiply());
case "/":
return(new OperatorDivide());
case "%":
return(new OperatorMod());
case "^":
return(new OperatorPower());
case "AND":
return(new OperatorBitAnd());
case "OR":
return(new OperatorBitOr());
case "XOR":
return(new OperatorBitXor());
case "<<":
return(new OperatorBitShiftLeft());
case ">>":
return(new OperatorBitShiftRight());
}
}
else
{
// 没有左操作数
switch (exp.ToUpper())
{
case "+":
return(new OperatorPositive());
case "-":
return(new OperatorNegative());
case "~":
return(new OperatorBitReverse());
}
}
// 不可判断者，返回空
return(null);
}
/// <summary>
/// ���Է���һ�����������
/// </summary>
/// <param name="exp">Ҫ���Ե��ַ���</param>
/// <param name="leftItem"></param>
/// <returns>����ɹ�������һ�����������ʵ�������ؿ�</returns>
private static OperatorBase TryGetOperator(string exp, IOperatorOrOperand leftItem)
{
// �ж�����Ƿ��Dz�����
bool hasLeftOperand = false;
if (leftItem == null)
{
// û������
hasLeftOperand = false;
}
else if (leftItem.IsOperand)
{
// �����Dz�����
hasLeftOperand = true;
}
else if (leftItem.GetType() == typeof(OperatorCloseBracket))
{
// �����DZ�����
hasLeftOperand = true;
}
else
{
// �������
hasLeftOperand = false;
}
// ���ݷ����ı��ж�
string symbol = exp.ToUpper();
switch (symbol)
{
case "(":
return new OperatorOpenBracket();
case ")":
return new OperatorCloseBracket();
}
// ���������������ж�
if (hasLeftOperand == true)
{
// �����������
switch (exp.ToUpper())
{
case "+":
return new OperatorPlus();
case "-":
return new OperatorMinus();
case "*":
return new OperatorMultiply();
case "/":
return new OperatorDivide();
case "%":
return new OperatorMod();
case "^":
return new OperatorPower();
case "AND":
return new OperatorBitAnd();
case "OR":
return new OperatorBitOr();
case "XOR":
return new OperatorBitXor();
case "<<":
return new OperatorBitShiftLeft();
case ">>":
return new OperatorBitShiftRight();
}
}
else
{
// û���������
switch (exp.ToUpper())
{
case "+":
return new OperatorPositive();
case "-":
return new OperatorNegative();
case "~":
return new OperatorBitReverse();
}
}
// �����ж��ߣ����ؿ�
return null;
}
