private QuickCalcParse Scan(string line)
{
QuickCalcParse parser = new QuickCalcParse();
StringBuilder result = new StringBuilder();
int index = 0; //获取形参s的每一个字符的索引
DFAState currentState = DFAState.Start; //当前DFA的状态
while (index < line.Length)
{ //DFA循环
switch (currentState)
{
case DFAState.Start:
if (char.IsWhiteSpace(line[index]))
{
}
else if (char.IsLetter(line[index]))
{
result.Append(line[index]);
currentState = DFAState.InId;
}
else if (char.IsDigit(line[index]))
{
result.Append(line[index]);
currentState = DFAState.InInt;
}
else if (line[index] == '.')
{
result.Append(line[index]);
currentState = DFAState.InDecimal;
}
else if (ALL_AVAILABLE_OP.Contains(line[index]))
{
result.Append(line[index]);
currentState = DFAState.InSym;
}
else
{
QuickCalcLog.Log("");
parser.Add(QuickCalcToken.Error, line);
}
index++;
break;
case DFAState.InInt:
if (line[index] == '.')
{
result.Append(line[index]);
currentState = DFAState.InDecimal;
}
else if (result[0] == '0' && (line[index] == 'x' || line[index] == 'X'))
{
result.Append(line[index]);
currentState = DFAState.InHex;
}
else if (!char.IsDigit(line[index]))
{
parser.Add(QuickCalcToken.Numeric, result.ToString()); //写入语法分析表
currentState = DFAState.Start;
result.Clear(); //清空字符串
index--; //回退
}
else if (char.IsDigit(line[index]))
{
result.Append(line[index]);
currentState = DFAState.InInt;
}
index++;
break;
case DFAState.InDecimal:
if (!char.IsDigit(line[index]))
{
parser.Add(QuickCalcToken.Numeric, result.ToString()); //写入语法分析表
currentState = DFAState.Start;
result.Clear(); //清空字符串
index--; //回退
}
else if (char.IsDigit(line[index]))
{
result.Append(line[index]);
}
index++;
break;
case DFAState.InHex:
if (char.IsDigit(line[index]) ||
(line[index] >= 'a' && line[index] <= 'f') ||
(line[index] >= 'A' && line[index] <= 'F'))
{
result.Append(line[index]);
}
else if (!char.IsDigit(line[index]))
{
parser.Add(QuickCalcToken.Numeric, result.ToString()); //写入语法分析表
currentState = DFAState.Start;
result.Clear(); //清空字符串
index--; //回退
}
index++;
break;
case DFAState.InId:
if (!char.IsLetter(line[index]))
{
if (isReserved(result.ToString())) //判断是否为关键字
{
parser.Add(QuickCalcToken.Reserved, result.ToString());
currentState = DFAState.Start;
result.Clear();
index--;
}
else
{
QuickCalcLog.Log("");
parser.Add(QuickCalcToken.Error, line);
}
}
else if (char.IsLetter(line[index]))
{
result.Append(line[index]);
currentState = DFAState.InId;
}
index++;
break;
case DFAState.InSym:
index--;
if (ALL_COMPARE_OP.Contains(line[index]))
{
currentState = DFAState.InCmp;
}
else
{
parser.Add(QuickCalcToken.Symbol, result.ToString());
currentState = DFAState.Start;
result.Clear();
}
index++;
break;
case DFAState.InCmp:
switch (line[index - 1])
{ //判断前一个字符是<,>,=还是!，他们只能后接=符号，否则将作为两个符号处理
case '>':
case '<':
case '=':
case '!':
if (line[index] == '=')
{
result.Append(line[index]);
parser.Add(QuickCalcToken.Symbol, result.ToString());
}
else
{ //作为两个符号保存
parser.Add(QuickCalcToken.Symbol, result.ToString());
index--;
}
index++;
currentState = DFAState.Start;
break;
case '&':
if (line[index] == '&')
{
result.Append(line[index]);
parser.Add(QuickCalcToken.Symbol, result.ToString());
index++;
}
else
{ //作为两个符号保存
parser.Add(QuickCalcToken.Symbol, result.ToString());
}
currentState = DFAState.Start;
result.Clear();
break;
case '|':
if (line[index] == '|')
{
result.Append(line[index]);
parser.Add(QuickCalcToken.Symbol, result.ToString());
index++;
}
else
{ //作为两个符号保存
parser.Add(QuickCalcToken.Symbol, result.ToString());
}
currentState = DFAState.Start;
result.Clear();
break;
}
break;
}
}
//处理字符串尾端的状态
switch (currentState)
{
case DFAState.InInt:
case DFAState.InDecimal:
case DFAState.InHex:
parser.Add(QuickCalcToken.Numeric, result.ToString()); //写入语法分析表
break;
case DFAState.InId:
if (isReserved(result.ToString()))
{ //判断是否为关键字
parser.Add(QuickCalcToken.Reserved, result.ToString());
}
else
{
parser.Add(QuickCalcToken.Error, result.ToString());
}
break;
case DFAState.InSym:
parser.Add(QuickCalcToken.Symbol, result.ToString());
break;
}
return(parser);
}
public double Eval(string line)
{
QuickCalcParse parser = Scan(line);
return(parser.Parse());
}