Nest all namespaces

The compiler supports this now.  We can type less going forward.
No functional changes.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I29d6fa4f9aacc0e381f1a7637294db0392466995
diff --git a/frc971/orin/apriltag.cc b/frc971/orin/apriltag.cc
index 1cb0f88..dd253d1 100644
--- a/frc971/orin/apriltag.cc
+++ b/frc971/orin/apriltag.cc
@@ -22,8 +22,7 @@
 #include "frc971/orin/threshold.h"
 #include "frc971/orin/transform_output_iterator.h"
 
-namespace frc971 {
-namespace apriltag {
+namespace frc971::apriltag {
 namespace {
 
 typedef std::chrono::duration<float, std::milli> float_milli;
@@ -1151,5 +1150,4 @@
   first_ = false;
 }
 
-}  // namespace apriltag
-}  // namespace frc971
+}  // namespace frc971::apriltag
diff --git a/frc971/orin/apriltag_detect.cc b/frc971/orin/apriltag_detect.cc
index eecc056..69c93cc 100644
--- a/frc971/orin/apriltag_detect.cc
+++ b/frc971/orin/apriltag_detect.cc
@@ -31,8 +31,7 @@
                           zarray_t *poly1);
 };
 
-namespace frc971 {
-namespace apriltag {
+namespace frc971::apriltag {
 namespace {
 
 void HostFitLine(LineFitMoments moments, double *lineparam01,
@@ -519,5 +518,4 @@
   zarray_sort(detections_, detection_compare_function);
 }
 
-}  // namespace apriltag
-}  // namespace frc971
+}  // namespace frc971::apriltag
diff --git a/frc971/orin/crcv_generator.cc b/frc971/orin/crcv_generator.cc
index 5c72385..a3f1f03 100644
--- a/frc971/orin/crcv_generator.cc
+++ b/frc971/orin/crcv_generator.cc
@@ -15,8 +15,8 @@
 // ahead-of-time optimized functions as directed by command-line arguments.
 // https://halide-lang.org/tutorials/tutorial_lesson_15_generators.html has an
 // introduction to much of the magic in this file.
-namespace frc971 {
-namespace orin {
+
+namespace frc971::orin {
 namespace {
 
 template <typename T>
@@ -142,8 +142,7 @@
   }
 };
 
-}  // namespace orin
-}  // namespace frc971
+}  // namespace frc971::orin
 
 HALIDE_REGISTER_GENERATOR(frc971::orin::YCbCr, ycbcr)
 HALIDE_REGISTER_GENERATOR(frc971::orin::YCbCr422, ycbcr422)
diff --git a/frc971/orin/cuda.cc b/frc971/orin/cuda.cc
index 89b1529..6bcc79c 100644
--- a/frc971/orin/cuda.cc
+++ b/frc971/orin/cuda.cc
@@ -7,8 +7,7 @@
     sync, false,
     "If true, force synchronization after each step to isolate errors better.");
 
-namespace frc971 {
-namespace apriltag {
+namespace frc971::apriltag {
 
 size_t overall_memory = 0;
 
@@ -25,5 +24,4 @@
   if (FLAGS_sync) CheckAndSynchronize(message);
 }
 
-}  // namespace apriltag
-}  // namespace frc971
+}  // namespace frc971::apriltag
diff --git a/frc971/orin/line_fit_filter.cc b/frc971/orin/line_fit_filter.cc
index 954976a..737079f 100644
--- a/frc971/orin/line_fit_filter.cc
+++ b/frc971/orin/line_fit_filter.cc
@@ -8,8 +8,7 @@
 
 // #define DEBUG_BLOB_NUMBER 401
 
-namespace frc971 {
-namespace apriltag {
+namespace frc971::apriltag {
 
 static_assert(sizeof(LineFitPoint) == 40, "Size of LineFitPoint changed");
 static_assert(sizeof(int4) == 16, "Size of int4 changed");
@@ -1231,5 +1230,4 @@
   return os;
 }
 
-}  // namespace apriltag
-}  // namespace frc971
+}  // namespace frc971::apriltag
diff --git a/frc971/orin/points.cc b/frc971/orin/points.cc
index dbf5496..7dc36f2 100644
--- a/frc971/orin/points.cc
+++ b/frc971/orin/points.cc
@@ -3,8 +3,7 @@
 #include <iomanip>
 #include <ostream>
 
-namespace frc971 {
-namespace apriltag {
+namespace frc971::apriltag {
 
 std::ostream &operator<<(std::ostream &os, const QuadBoundaryPoint &point) {
   std::ios_base::fmtflags original_flags = os.flags();
@@ -31,5 +30,4 @@
 
 static_assert(sizeof(IndexPoint) == 8, "IndexPoint didn't pack right.");
 
-}  // namespace apriltag
-}  // namespace frc971
+}  // namespace frc971::apriltag
diff --git a/frc971/orin/threshold.cc b/frc971/orin/threshold.cc
index 79ccced..4254b71 100644
--- a/frc971/orin/threshold.cc
+++ b/frc971/orin/threshold.cc
@@ -4,8 +4,7 @@
 
 #include "frc971/orin/cuda.h"
 
-namespace frc971 {
-namespace apriltag {
+namespace frc971::apriltag {
 namespace {
 
 // 1280 -> 2 * 128 * 5
@@ -202,5 +201,4 @@
   }
 }
 
-}  // namespace apriltag
-}  // namespace frc971
+}  // namespace frc971::apriltag
diff --git a/frc971/orin/transform_output_iterator.h b/frc971/orin/transform_output_iterator.h
index 051baea..cdda637 100644
--- a/frc971/orin/transform_output_iterator.h
+++ b/frc971/orin/transform_output_iterator.h
@@ -1,8 +1,7 @@
 #ifndef FRC971_TRANSFORM_OUTPUT_ITERATOR_
 #define FRC971_TRANSFORM_OUTPUT_ITERATOR_
 
-namespace frc971 {
-namespace apriltag {
+namespace frc971::apriltag {
 
 // template class that allows conversions at the output of a cub algorithm
 template <typename InputType, typename OutputType, typename ConversionOp,
@@ -86,7 +85,6 @@
   OutputType *ptr;
 };
 
-}  // namespace apriltag
-}  // namespace frc971
+}  // namespace frc971::apriltag
 
 #endif  // FRC971_TRANSFORM_OUTPUT_ITERATOR_