fix some bugs under gcc 4.8.5

source/sample/transformer/t2tdata/DataSet.cpp

@@ -30,11 +30,11 @@
 
 using namespace nts;
 
-bool Compare(Example& a, Example& b) {
+bool Compare(const Example& a, const Example& b) {
     return a.values.size() > b.values.size();
 }
 
-bool CompareRes(Result& a, Result& b) {
+bool CompareRes(const Result& a, const Result& b) {
     return a.id < b.id;
 }
 

source/sample/transformer/t2tdata/DataSet.h

@@ -46,6 +46,10 @@ struct Result {
 using BufferType = vector<Example>;
 using ResBufferType = vector<Result>;
 
+bool Compare(const Example& a, const Example& b);
+
+bool CompareRes(const Result& a, const Result& b);
+
 namespace nts { // namespace nts(NiuTrans.Tensor)
 
 /* A `DataSet` is associated with a file which contains variable length data.*/

source/sample/transformer/t2tdata/StringUtil.h

@@ -90,17 +90,6 @@ inline vector<uint8_t> Split(const string& s, const string& delimiter)
     return fields;
 }
 
-template <>
-inline vector<bool> Split(const string& s, const string& delimiter)
-{
-    vector<bool> fields;
-    for (const auto& p : SplitToPos(s, delimiter)) {
-        fields.emplace_back(
-            static_cast<bool>(strtol(s.data() + p.first, nullptr, 10)));
-    }
-    return fields;
-}
-
 } // namespace nts
 
 #endif // __STRING_UTIL_H__