Fix mac compilation (#618)

include/dgl/immutable_graph.h

@@ -91,7 +91,7 @@ class CSR : public GraphInterface {
   }
 
   bool HasVertex(dgl_id_t vid) const override {
-    return vid < NumVertices() && vid >= 0;
+    return vid < NumVertices();
   }
 
   bool HasEdgeBetween(dgl_id_t src, dgl_id_t dst) const override;
@@ -311,7 +311,7 @@ class COO : public GraphInterface {
   }
 
   bool HasVertex(dgl_id_t vid) const override {
-    return vid < NumVertices() && vid >= 0;
+    return vid < NumVertices();
   }
 
   bool HasEdgeBetween(dgl_id_t src, dgl_id_t dst) const override {
@@ -345,7 +345,7 @@ class COO : public GraphInterface {
   }
 
   std::pair<dgl_id_t, dgl_id_t> FindEdge(dgl_id_t eid) const override {
-    CHECK(eid < NumEdges() && eid >= 0) << "Invalid edge id: " << eid;
+    CHECK(eid < NumEdges()) << "Invalid edge id: " << eid;
     const dgl_id_t* src_data = static_cast<dgl_id_t*>(src_->data);
     const dgl_id_t* dst_data = static_cast<dgl_id_t*>(dst_->data);
     return std::make_pair(src_data[eid], dst_data[eid]);

src/c_api_common.h

@@ -12,7 +12,6 @@
 #include <algorithm>
 #include <vector>
 
-namespace {
 /*! \brief Check whether two device contexts are the same.*/
 inline bool operator == (const DLContext& ctx1, const DLContext& ctx2) {
   return ctx1.device_type == ctx2.device_type && ctx1.device_id == ctx2.device_id;
@@ -22,7 +21,6 @@ inline bool operator == (const DLContext& ctx1, const DLContext& ctx2) {
 inline std::ostream& operator << (std::ostream& os, const DLContext& ctx) {
   return os << "" << ctx.device_type << ":" << ctx.device_id << "";
 }
-}  // namespace
 
 namespace dgl {