public string ToHalfWidth(string str = null)
{
return(ResultPipe(StringTool.ToHalfWidth(str)));
}
/// <summary>
/// 算术逆波兰表达式生成（也叫后缀表达式）Reverse Polish Notation
/// </summary>
/// 首先构造一个运算符栈，此运算符在栈内遵循越往栈顶优先级越高的原则
/// 如果当前字符为变量或者为数字，则压栈，如果是运算符，则将栈顶两个元素弹出作相应运算，结果再入栈，最后当表达式扫描完后，栈里的就是结果。
///
///参考 https://bbs.csdn.net/topics/200010856
private string BuildingRPN(string originExpression)
{
originExpression = originExpression.ToLower();//仅支持小写
#region 先把所有支持的函数名替换为单个字符
originExpression = StringTool.ToHalfWidth(originExpression);
if (originExpression.IsMatch("[a-z]"))
{
originExpression = originExpression.ReplaceAllFromPairSet(_supportFunction);
}
#endregion
StringBuilder originStr = new StringBuilder(originExpression); //存入要转成的字符串为stringBuilder
Stack operatorStack = new Stack(); //运算符栈
StringBuilder parsingStr = new StringBuilder(); //存放处理后的结果
char nowChar = ' '; //遍历用当前字符
//这一步遍历是挑出有用的字符，去除一些空格或无用字符等干扰因素
for (int i = 0;
i < originStr.Length;
i++)
{
nowChar = originStr[i];
//added c==',' for german culture
if (char.IsDigit(nowChar) || nowChar == ',')//数字当然要了.
{
parsingStr.Append(nowChar);
}
else if (char.IsWhiteSpace(nowChar))
{
continue;
}
else if (char.IsLetter(nowChar))//注意可能会有用户乱输入的字母 还未处理
{
parsingStr.Append(nowChar);
}
else
{
switch (nowChar)//如果是其它字符...列出的要,没有列出的不要.
{
case '+':
case '-':
case '*':
case '/':
case '%':
case '^':
case '!':
case '(':
case ')':
case '.':
parsingStr.Append(nowChar);
break;
default:
continue;
}
}
}
originStr = new StringBuilder(parsingStr.ToString());
#region 对负号进行预转义处理.负号变单目运算符求反.
for (int i = 0; i < originStr.Length - 1; i++)
{
if (originStr[i] == '-' && (i == 0 || originStr[i - 1] == '('))//这里是支持开头为负号的数字，但中间有数字负号必须用括号括起来
{
originStr[i] = '!';
}
}
//字符转义.
#endregion
#region 将中缀表达式变为后缀表达式.
parsingStr = new StringBuilder();
for (int i = 0; i < originStr.Length; i++)
{
if (char.IsDigit(originStr[i]) || originStr[i] == '.')//如果是数值.
{
parsingStr.Append(originStr[i]);
//加入后缀式
}
else if (originStr[i] == '+' ||
originStr[i] == '-' ||
originStr[i] == '*' ||
originStr[i] == '/' ||
originStr[i] == '%' ||
originStr[i] == '^' ||
originStr[i] == '!' ||
isInSupportedArray(originStr[i]))
{
#region 运算符处理 主要按照优先级刷新运算顺序
while (operatorStack.Count > 0) //栈不为空时
{
nowChar = (char)operatorStack.Pop();
//将栈中的操作符弹出.
if (nowChar == '(') //如果发现左括号.停.
{
operatorStack.Push(nowChar);
//将弹出的左括号压回.因为还有右括号要和它匹配.
break;
//中断.
}
else
{
if (Power(nowChar) < Power(originStr[i]))//如果优先级比上次的高,则压栈.
{
operatorStack.Push(nowChar);
break;
}
else
{
parsingStr.Append(' ');
parsingStr.Append(nowChar);
}
//如果不是左括号,那么将操作符加入后缀式中.
}
}
operatorStack.Push(originStr[i]);
//把新操作符入栈.
parsingStr.Append(' ');
#endregion
}
else if (originStr[i] == '(')//基本优先级提升
{
operatorStack.Push('(');
parsingStr.Append(' ');
}
else if (originStr[i] == ')') //基本优先级下调
{
while (operatorStack.Count > 0) //栈不为空时
{
nowChar = (char)operatorStack.Pop();
//pop Operator
if (nowChar != '(')
{
parsingStr.Append(' ');
parsingStr.Append(nowChar);
//加入空格主要是为了防止不相干的数据相临产生解析错误.
parsingStr.Append(' ');
}
else
{
break;
}
}
}
else
{
parsingStr.Append(originStr[i]);
}
}
while (operatorStack.Count > 0)//这是最后一个弹栈啦.
{
parsingStr.Append(' ');
parsingStr.Append(operatorStack.Pop());
}
#endregion
parsingStr.Append(' ');
return(FormatSpace(parsingStr.ToString()));
//在这里进行一次表达式格式化.这里就是后缀式了.
}
