fixed cpplint error about namespace using-directives (#2836)

include/LightGBM/tree_learner.h

@@ -13,10 +13,10 @@
 
 #include <LightGBM/json11.hpp>
 
-using namespace json11;
-
 namespace LightGBM {
 
+using json11::Json;
+
 /*! \brief forward declaration */
 class Tree;
 class Dataset;

src/boosting/gbdt.h

@@ -24,10 +24,10 @@
 #include <LightGBM/json11.hpp>
 #include "score_updater.hpp"
 
-using namespace json11;
-
 namespace LightGBM {
 
+using json11::Json;
+
 /*!
 * \brief GBDT algorithm implementation. including Training, prediction, bagging.
 */

src/io/dataset_loader.cpp

@@ -13,10 +13,10 @@
 
 #include <LightGBM/json11.hpp>
 
-using namespace json11;
-
 namespace LightGBM {
 
+using json11::Json;
+
 DatasetLoader::DatasetLoader(const Config& io_config, const PredictFunction& predict_fun, int num_class, const char* filename)
   :config_(io_config), random_(config_.data_random_seed), predict_fun_(predict_fun), num_class_(num_class) {
   label_idx_ = 0;

src/treelearner/gpu_tree_learner.h

@@ -34,10 +34,10 @@
 #include <boost/compute/container/vector.hpp>
 #include <boost/align/aligned_allocator.hpp>
 
-using namespace json11;
-
 namespace LightGBM {
 
+using json11::Json;
+
 /*!
 * \brief GPU-based parallel learning algorithm.
 */

src/treelearner/serial_tree_learner.h

@@ -30,9 +30,10 @@
 #include <boost/align/aligned_allocator.hpp>
 #endif
 
-using namespace json11;
-
 namespace LightGBM {
+
+using json11::Json;
+
 /*! \brief forward declaration */
 class CostEfficientGradientBoosting;
 /*!