public static bool parse_tokens()
{
try
{
all_tokens.Clear();
stack_to_parse = new Stack <object>();
StateStackElement initial_state = new StateStackElement(1);
stack_to_parse.Push(initial_state);
foreach (Token t in MainWindow.allTokens)
{
all_tokens.Add(t);
}
while (all_tokens.Count != 0)
{
//获取分析栈的状态（第一个状态元素）
StateStackElement first = (StateStackElement)(stack_to_parse.Peek());
//获取剩余tokens的第一个
Token t = all_tokens[0];
//根据第一个token，构建一个栈元素（type_code自动赋予，用来判断token是哪一种stackelement）
StackElement ele = (StackElement)Tools.transformTokenToSymbol(t);
//结合分析表，获取应该进行的语法动作
Action a = getActionByTransformedToken(first.state, ele.type_code, t.content);
//进行该语法动作
conductAction(a, t, ele, first);
}
//下面这部分就与tokens无关了，如果上面tokens没有出错，就会进入下面的收尾部分：
while (true)
{
//这部分的意义主要是在于，tokens一旦为空，上面的while循环自动结束，但是这并不意味着语法分析的结束
//程序只是进行了最后一次真正token的移入，但是还有很多规约，甚至是报错的工作要进行
//这一部分每次都会接收到一个我们固定的empty，如果程序认为它不能在empty下规约，那么要么是到了最后的E，要么是报错
StateStackElement last_state = (StateStackElement)stack_to_parse.Peek();
Action last_action = GrammerConfig.analysis_table[last_state.state]["empty"];
//执行语法动作，应该是一个规约，否则就是已经规约到头err，那就是结束err
if (last_action.action == "reduce")
{
//规约产生的肯定都是非终结符
NonterminalStackElement e = new NonterminalStackElement(-1, last_action.left);
int count = last_action.right.Count;
for (int i = 0; i < count * 2; i++)
{
if (i % 2 == 1)
{
StackElement s = (StackElement)stack_to_parse.Pop();
s.layersIncreaseRecursively();
e.branches.Insert(0, s);
}
else
{
stack_to_parse.Pop();
}
}
StateStackElement first_now = (StateStackElement)(stack_to_parse.Peek());
Console.WriteLine("last_action.left:" + last_action.left);
Action aa = getActionByTransformedToken(first_now.state, e.type_code, last_action.left);
if (aa.action == "shift")
{
stack_to_parse.Push(e);
stack_to_parse.Push(new StateStackElement(aa.new_state));
}
else if (aa.action == "error")
{
stack_to_parse.Push(e);
stack_to_parse.Push(new StateStackElement(0));
break;
}
else if (aa.action == "acc")
{
stack_to_parse.Push(e);
stack_to_parse.Push(new StateStackElement(0));
break;
}
else
{
throw new ParserException("规约之后难道不是移进吗");
}
}
else if (last_action.action == "error")
{
throw new ParserException("程序定义不完整或者出现错误");
}
else if (last_action.action == "acc")
{
stack_to_parse.Push(new StateStackElement(0));
break;
}
else if (last_action.action == "special action")
{
throw new ParserException("程序定义不完整或者出现错误");
}
else
{
MessageBox.Show(last_action.action);
throw new ParserException("不可能的情况");
}
}
printStack();
AbstractSyntaxTree ast_window = new AbstractSyntaxTree();
if (MainWindow.grammer_output)
{
ast_window.Show();
}
return(true);
}
catch (ParserException pe)
{
MessageBox.Show(pe.getExceptionMsg());
return(false);
}
catch (Exception ee)
{
MessageBox.Show(ee.ToString());
return(false);
}
}
//执行五种语法动作之一 语法动作 - 目前的第一个token - 根据token构建的栈元素
private static void conductAction(Action a, Token t, StackElement ele, StateStackElement first)
{
if (a.action == "error")
{
throw new ParserException("第" + t.lineNum + "行：" + "遇到无法解析的语法成分:" + Token.getALineOfTokens(t.lineNum));
}
else if (a.action == "shift")
{
stack_to_parse.Push(ele);
stack_to_parse.Push(new StateStackElement(a.new_state));
all_tokens.RemoveAt(0);
}
else if (a.action == "reduce")
{
//规约产生的肯定都是非终结符
NonterminalStackElement e = new NonterminalStackElement(-1, a.left);
int count = a.right.Count;
for (int i = 0; i < count * 2; i++)
{
//第偶数个pop出去的元素不是代表状态的元素，是需要规约的元素
if (i % 2 == 1)
{
//保证是子结点是顺序的
StackElement s = (StackElement)stack_to_parse.Pop();
s.layersIncreaseRecursively();
e.branches.Insert(0, s);
}
else
{
stack_to_parse.Pop();
}
}
StateStackElement first_now = (StateStackElement)(stack_to_parse.Peek());
Action aa = getActionByTransformedToken(first_now.state, e.type_code, a.left);
if (aa.action == "shift")
{
stack_to_parse.Push(e);
stack_to_parse.Push(new StateStackElement(aa.new_state));
}
else
{
throw new ParserException("规约之后难道不是移进吗");
}
}
else if (a.action == "special action")
{
//根据当前状态，将自动移入的nullable非终结符，获取分析表要我们执行的动作
Action next_action = GrammerConfig.analysis_table[first.state][a.auto_shifted];
if (next_action.action == "shift")
{
stack_to_parse.Push(new NonterminalStackElement(-1, a.auto_shifted));
stack_to_parse.Push(new StateStackElement(next_action.new_state));
}
else
{
throw new ParserException("special action自动移入才对呀");
}
}
else
{
throw new ParserException("还未实现acc");
}
}