Fixes #698:

* Added a `device::default_()` function for obtaining the default CUDA device
* Added a bit of code using `device::default_()` to the `device_management` example program

examples/by_api_module/device_management.cpp

@@ -40,6 +40,13 @@ void basics(cuda::device::id_t device_id)
 		die_("The device's reported ID and the ID for which we created the device differ: "
 		+ std::to_string(device.id()) + " !=" +  std::to_string(device_id));
 	}
+
+	if (device.id() == cuda::device::default_device_id) {
+		auto default_device = cuda::device::default_();
+		if (device != default_device) {
+			die_("A device with the default device ID was not equal to the default CUDA device");
+		}
+	}
 }
 
 void attributes_and_properties()

src/cuda/api/device.hpp

@@ -845,6 +845,11 @@ inline device_t get(id_t id)
 	return wrap(id);
 }
 
+inline device_t default_()
+{
+	return get(cuda::device::default_device_id);
+}
+
 /**
  * A named constructor idiom for a "dummy" CUDA device representing the CPU.
  *