/// <summary>
/// 将字符串解析为中序表达式
/// </summary>
/// <param name="str">要解析的字符串</param>
/// <returns>一个中序表达式结构体</returns>
static public MiddleExpression TurnToMiddle(string str)
{
string s = str.Replace(" ", "");
MiddleExpression m = new MiddleExpression();
CalcNode LastNode = new CalcNode(NodeType.Num);
char[] cs = s.ToCharArray();
LastNode = null;
foreach (char c in cs)
{
if (c >= 48 && c <= 57)
{
if (LastNode != null && LastNode.Type == NodeType.Num)
{
LastNode.Num = LastNode.Num * 10 + c - 48;
}
else
{
LastNode = CalcNode.FromDouble(c - 48.0);
m.Add(LastNode);
}
}
else if (Operators.Contains(c))
{
LastNode = CalcNode.FromChar(c);
m.Add(LastNode);
}
else
{
if (LastNode != null && LastNode.Type == NodeType.Variable)
{
LastNode.Value += c;
}
else
{
LastNode = new CalcNode(NodeType.Variable);
LastNode.Value = c.ToString();
m.Add(LastNode);
}
}
}
// 检查是否有计算节点是函数
foreach (CalcNode node in m)
{
if (node.Type == NodeType.Variable)
{
if (Functions.Contains(node.Value))
{
node.Type = NodeType.Function;
}
}
}
return(m);
}
static public QuickCalculator FromString(String s)
{
try
{
MiddleExpression m = TurnToMiddle(s);
PolishExpression p = TurnToPolish(m);
QuickCalculator q = TurnToMachine(p);
return(q);
}
catch
{
return(null);
}
}
static public MiddleExpression TurnToMiddle(string str)
{
string s = str.Replace(" ", "");
MiddleExpression m = new MiddleExpression();
CalcNode LastNode = new CalcNode(NodeType.Num);
char[] cs = s.ToCharArray();
LastNode = null;
foreach (char c in cs)
{
if (c >= 48 && c <= 57)
{
if (LastNode != null && LastNode.Type == NodeType.Num)
{
LastNode.Num = LastNode.Num * 10 + c - 48;
}
else
{
LastNode = CalcNode.FromDouble(c - 48.0);
m.Add(LastNode);
}
}
else if (c == '+' || c == '-' || c == '*' || c == '/' || c == '%' || c == '^' || c == '(' || c == ')')
{
LastNode = CalcNode.FromChar(c);
m.Add(LastNode);
}
else
{
LastNode = new CalcNode(NodeType.Variable);
LastNode.Value = c;
m.Add(LastNode);
}
}
return(m);
}
static public PolishExpression TurnToPolish(MiddleExpression f)
{
Stack <CalcNode> S1 = new Stack <CalcNode>();
Stack <CalcNode> S2 = new Stack <CalcNode>();
S1.Push(new CalcNode(NodeType.Operator));
PolishExpression e = new PolishExpression();
foreach (CalcNode node in f)
{
if (node.Type == NodeType.Operator)
{
if (node.Value == '(')
{
S1.Push(node);
}
else if (node.Value == ')')
{
CalcNode LastNode = S1.Pop();
while (LastNode.Value != '(')
{
S2.Push(LastNode);
LastNode = S1.Pop();
}
}
else
{
if (S1.Peek().Value == '(')
{
S1.Push(node);
}
else
{
int rank = Rank(node.Value);
int Toprank = Rank(S1.Peek().Value);
if (rank <= Toprank)
{
while (!(S2.Peek().Value == '(' || Rank(S1.Peek().Value) < rank))
{
S2.Push(S1.Pop());
}
}
S1.Push(node);
}
}
}
else
{
S2.Push(node);
}
}
if (S1.Count != 0)
{
while (S1.Count > 1)
{
S2.Push(S1.Pop());
}
}
PolishExpression p = new PolishExpression();
while (S2.Count > 0)
{
p.Push(S2.Pop());
}
return(p);
}
