diff --git a/LogicalCircuit.pro.user b/LogicalCircuit.pro.user
index 479c242..5f6f0fb 100644
--- a/LogicalCircuit.pro.user
+++ b/LogicalCircuit.pro.user
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE QtCreatorProject>
-<!-- Written by QtCreator 4.2.1, 2019-04-17T00:31:02. -->
+<!-- Written by QtCreator 4.2.1, 2019-04-22T17:49:54. -->
 <qtcreator>
  <data>
   <variable>EnvironmentId</variable>
diff --git a/gate.h b/gate.h
index ef28c53..3ec8682 100644
--- a/gate.h
+++ b/gate.h
@@ -205,7 +205,7 @@ class tri : public gate
 public:
     tri(string name,uint inputNum, uint outputNum=1) : gate(name,inputNum,outputNum) { isTri=true; }
 
-    const uint Q=0;
+    const static uint Q=0;
     virtual void setQ(bool q) { stat[Q]=q; }
     virtual bool getQ() { return stat[Q]; }
     blist getStat() { return stat; }
diff --git a/node.cpp b/node.cpp
index ea43838..d4bea71 100644
--- a/node.cpp
+++ b/node.cpp
@@ -11,6 +11,11 @@ line::line(string name, node *n, uint sub) : name(name), n(n), sub(sub)
     nodeManager::addLine(this);
 }
 
+bool line::getIsEvaling()
+{
+    return this->n->isEvaling;
+}
+
 bool line::get()
 {
     if(isConst)
diff --git a/node.h b/node.h
index 1888381..f1334ce 100644
--- a/node.h
+++ b/node.h
@@ -10,16 +10,18 @@ class line
 {
 private:
     string name;
-    node *n;
     uint sub;
     bool isConst=false;
+
 public:
+    node *n;
     bool constVal;
 
     line(string name, node *n,uint sub=0);
     line(string name,bool constVal=0) : name(name), isConst(true), constVal(constVal) {}
     bool get();
     string getName() { return this->name; }
+    bool getIsEvaling();
     void stru(uint tabNum=0);
 };
 
@@ -31,13 +33,28 @@ class node
     {
         blist par;
         for(line* i : inputLine)
-            par.push_back(i->get());
+        {
+            if(i->getIsEvaling()) //检查是否有环形
+            {
+                 gate* iTri=i->n->g;
+                 if(iTri->getIsTri())
+                 {
+                     tri* t=(tri*)iTri;
+                     par.push_back(t->getStat()[tri::Q]);
+                 }
+                 else
+                     throw string("Illegal Ring Circuit");
+            }
+            else
+                par.push_back(i->get());
+        }
         return par;
     }
 
 public:
     vector<line*> inputLine; //与g的input个数相等。每个连接需指明插槽位
-    bool isEval=false;
+    bool isEvaled=false;
+    bool isEvaling=false;
     blist result;
     gate *g;
 
@@ -47,11 +64,13 @@ class node
 
     blist eval()
     {
-        if(isEval==false)
+        isEvaling=true;
+        if(isEvaled==false)
         {
             this->result=g->calu(getInputPar());
-            this->isEval=true;
+            this->isEvaled=true;
         }
+        isEvaling=false;
         return this->result;
     }
 
@@ -102,7 +121,7 @@ class nodeManager
     static void resetChunk()
     {
         for(node* i : allNode)
-            i->isEval=false;
+            i->isEvaled=false;
     }
 
 public: