//后序表达式求值
private string PostfixEval(string postExp)
{
Stack<double> result = new Stack<double>();
double x, y;
for (int i = 0; i <= postExp.Length - 1; i++)
{
Operator op = new Operator(postExp[i]);
if (IsDigit(postExp[i]))
{
string operand = "";
while ((i <= postExp.Length - 1) && IsDigit(postExp[i]))
{
operand += postExp[i];
i++;
}
i--;
result.Push(Convert.ToDouble(operand));
continue;
}
if (postExp[i] == ' ') continue;
if (op.isSingle)
{
y = result.Pop();
result.Push(op.Parse(y));
}
else
{
y = result.Pop();
x = result.Pop();
result.Push(op.Parse(x, y));
}
}
return Convert.ToString(result.Peek());
}
//初始化
private void ExpInit(ref string exp)
{
Operator op = new Operator();
//全/半角&中/英文
exp = exp.Replace('（', '(');
exp = exp.Replace('）', ')');
exp = exp.Replace('。', '.');
exp = exp.Replace('，', '.');
exp = exp.Replace(',', '.');
exp = exp.Replace('[', '(');
exp = exp.Replace(']', ')');
exp = exp.Replace('{', '(');
exp = exp.Replace('}', ')');
exp = exp.Replace('【', '(');
exp = exp.Replace('】', ')');
exp = exp.Replace('『', '(');
exp = exp.Replace('』', ')');
exp = exp.Replace('_', '-');
exp = exp.Replace('\\', '/');
exp = exp.Replace('П', 'π');
//在括号/数字/函数/常数间插入乘号
bool afterBracket = false;
bool afterNum = false;
bool afterNumSpace = false;
bool afterConst = false;
for (int i = 0; i <= exp.Length - 1; i++)
{
if (op.FindFunc(exp, i) && (afterBracket || afterNum || afterNumSpace || afterConst)) //当前是函数,之前有括号/数字/常数
{
exp = exp.Insert(i, "*");
i += 1;
}
if (op.FindConst(exp, i) && (afterBracket || afterNum || afterNumSpace || afterConst)) //当前是常数,之前有括号/数字/常数
{
exp = exp.Insert(i, "*");
i += 1;
}
if ((exp[i] == '(') && (afterBracket || afterNum || afterNumSpace || afterConst)) //当前是括号,之前有括号/数字/常数
exp = exp.Insert(i, "*");
if (IsDigit(exp[i]) && (afterBracket || afterNumSpace || afterConst)) //当前是数字,之前有括号/数字+空白/常数
exp = exp.Insert(i, "*");
if (IsDigit(exp[i])) //在数字后
{
afterBracket = false;
afterNum = true;
afterNumSpace = false;
afterConst = false;
continue;
}
if (exp[i] == ')') //在右括号后
{
afterBracket = true;
afterNum = false;
afterNumSpace = false;
afterConst = false;
continue;
}
if (op.FindConst(exp, i)) //在常数后
{
afterBracket = false;
afterNum = false;
afterNumSpace = false;
afterConst = true;
i += op.opStr.Length - 1;
continue;
}
afterNumSpace = afterNum || afterNumSpace;//在数字与空白符后
if (op.FindWhole(exp, i) || (exp[i] == '('))
{
afterBracket = false;
afterNum = false;
afterNumSpace = false;
afterConst = false;
if (op.FindWhole(exp, i)) i += op.opStr.Length - 1;
continue;
}
}
//替换常数
for (int i = 0; i <= exp.Length - 1; i++)
{
if (op.FindConst(exp, i))
{
exp = exp.Remove(i, op.opStr.Length);
switch (op.opStr)
{
case "en":
exp = exp.Insert(i, Convert.ToString(Math.E));
break;
case "pi":
case "π":
exp = exp.Insert(i, Convert.ToString(Math.PI));
break;
case "m1":
exp = exp.Insert(i, M[1]);
break;
case "m2":
exp = exp.Insert(i, M[2]);
break;
case "m3":
exp = exp.Insert(i, M[3]);
break;
case "m4":
exp = exp.Insert(i, M[4]);
break;
}
}
}
//预处理正负号
char[] tempExp = exp.ToCharArray();
bool afterOp = true;
bool foundOp;
for (int i = 0; i <= exp.Length - 1; i++)
{
if ((exp[i] == '+') && afterOp) tempExp[i] = '~';
if ((exp[i] == '-') && afterOp) tempExp[i] = '_';
foundOp = false;
if (op.FindWhole(exp, i) || (exp[i] == '('))
{
afterOp = true;
foundOp = true;
if (op.FindWhole(exp, i)) i += op.opStr.Length - 1;
}
if (!foundOp) afterOp = false;
}
exp = new string(tempExp);
}
//中序转后序
private string InfixToPostfix(string exp)
{
string postExp = "";
Stack<char> operatorStack = new Stack<char>();
for (int i = 0; i <= exp.Length - 1; i++)
{
//数字添加至结果字符串
if (IsDigit(exp[i]))
{
postExp += exp[i];
continue;
}
if (exp[i] == '(')
{
operatorStack.Push('(');
continue;
}
if (exp[i] == ')')
{
while (operatorStack.Count > 0)
{
char topOp = operatorStack.Pop();
if (topOp == '(') break;
else postExp += topOp;
}
continue;
}
Operator nowOp = new Operator();
if (nowOp.FindWhole(exp, i))
{
while (operatorStack.Count > 0)
{
Operator topOp = new Operator(operatorStack.Pop());
//弹出优先级更高的运算符并添加至结果字符串
if ((topOp.priorLvl > nowOp.priorLvl) || nowOp.isRComb)
{
operatorStack.Push(topOp.opChar);
break;
}
else postExp += topOp.opChar;
}
//压入当前运算符
operatorStack.Push(nowOp.opChar);
postExp += ' ';
i += nowOp.opStr.Length - 1;
}
}
//弹出所有运算符
while (operatorStack.Count > 0) postExp += operatorStack.Pop();
return postExp;
}
