diff --git a/nasal_gc.h b/nasal_gc.h
index 4746d8d..651e71b 100644
--- a/nasal_gc.h
+++ b/nasal_gc.h
@@ -633,10 +633,10 @@ void nasal_gc::info()
         "hash ","upval","obj  ",
         "co   "
     };
-    std::cout<<"\ngarbage collector info:\n";
+    std::cout<<"\ngarbage collector info\n";
     for(uint8_t i=vm_str;i<vm_type_size;++i)
         std::cout<<"  "<<name[i]<<" | "<<count[i]<<"\n";
-    std::cout<<"\nmemory allocator info(max size):\n";
+    std::cout<<"\nmemory allocator info(max size)\n";
     for(uint8_t i=vm_str;i<vm_type_size;++i)
         std::cout<<"  "<<name[i]<<" | "<<initialize[i]+size[i]*increment[i]<<"(+"<<size[i]<<")\n";
 }
diff --git a/nasal_vm.h b/nasal_vm.h
index a6c03a9..0591807 100644
--- a/nasal_vm.h
+++ b/nasal_vm.h
@@ -363,7 +363,7 @@ void nasal_vm::opcallsort(const uint64_t* arr)
         opcall.end(),
         [](op& a,op& b){return a.second>b.second;}
     );
-    std::cout<<"\noperands call info:";
+    std::cout<<"\noperands call info";
     uint64_t total=0;
     for(auto& i:opcall)
     {
@@ -386,7 +386,7 @@ void nasal_vm::die(std::string str)
 inline bool nasal_vm::condition(nasal_ref val)
 {
     if(val.type==vm_num)
-        return val.value.num;
+        return val.num();
     else if(val.type==vm_str)
     {
         double num=str2num(val.str().c_str());
diff --git a/test/bp.nas b/test/bp.nas
index ccf8814..7326b08 100644
--- a/test/bp.nas
+++ b/test/bp.nas
@@ -11,6 +11,16 @@ var new_neuron=func()
     };
 }
 
+var tanh=func(x)
+{
+    var (a,b)=(math.exp(x),math.exp(-x));
+    return (a-b)/(a+b);
+}
+var difftanh=func(x)
+{
+    x=tanh(x);
+    return 1-x*x;
+}
 var sigmoid=func(x)
 {
     return 1/(1+math.exp(-x));
@@ -21,7 +31,7 @@ var diffsigmoid=func(x)
     return x*(1-x);
 }
 
-var (inum,hnum,onum,lr)=(2,4,1,0.1);
+var (inum,hnum,onum)=(2,4,1);
 var training_set=[[0,0],[0,1],[1,0],[1,1]];
 var expect=[0,1,1,0];
 
@@ -30,8 +40,8 @@ for(var i=0;i<hnum;i+=1)
 {
     append(hidden,new_neuron());
     for(var j=0;j<inum;j+=1)
-        append(hidden[i].w,2*rand());
-    hidden[i].bia=5*rand();
+        append(hidden[i].w,rand()>0.5?-2*rand():2*rand());
+    hidden[i].bia=rand()>0.5?-5*rand():5*rand();
 }
 
 var output=[];
@@ -39,8 +49,8 @@ for(var i=0;i<onum;i+=1)
 {
     append(output,new_neuron());
     for(var j=0;j<hnum;j+=1)
-        append(output[i].w,2*rand());
-    output[i].bia=5*rand();
+        append(output[i].w,rand()>0.5?-2*rand():2*rand());
+    output[i].bia=rand()>0.5?-5*rand():5*rand();
 }
 
 var forward=func(x)
@@ -51,7 +61,7 @@ var forward=func(x)
         hidden[i].in=hidden[i].bia;
         for(var j=0;j<inum;j+=1)
             hidden[i].in+=hidden[i].w[j]*input[j];
-        hidden[i].out=sigmoid(hidden[i].in);
+        hidden[i].out=tanh(hidden[i].in);
     }
     for(var i=0;i<onum;i+=1)
     {
@@ -70,7 +80,7 @@ var run=func(vec)
         hidden[i].in=hidden[i].bia;
         for(var j=0;j<inum;j+=1)
             hidden[i].in+=hidden[i].w[j]*input[j];
-        hidden[i].out=sigmoid(hidden[i].in);
+        hidden[i].out=tanh(hidden[i].in);
     }
     for(var i=0;i<onum;i+=1)
     {
@@ -94,7 +104,7 @@ var backward=func(x)
         hidden[i].diff=0;
         for(var j=0;j<onum;j+=1)
             hidden[i].diff+=output[j].w[i]*output[j].diff;
-        hidden[i].diff*=diffsigmoid(hidden[i].in);
+        hidden[i].diff*=difftanh(hidden[i].in);
     }
     for(var i=0;i<hnum;i+=1)
     {
diff --git a/test/json.nas b/test/json.nas
index 1de6b9d..b8b14be 100644
--- a/test/json.nas
+++ b/test/json.nas
@@ -226,6 +226,8 @@ var JSON=func(){
     var member=func(hash)
     {
         var name=token.content;
+        if(token.type==j_rbrace)
+            return;
         if(token.type==j_str)
             match(j_str);
         else
@@ -316,6 +318,10 @@ var ss=JSON.stringify({
         m3:[114514],
         m4:{year:1919,month:8,date:10}
     },
+    emptyhash:{},
+    emptyvec:[],
+    empty:[{}],
+    empty_an:[[[[[[{}]]]]]],
     function:func(){}
 });
 println(ss);