grains: implementation with warning

cpp/grains/grains.h

@@ -0,0 +1,14 @@
+#pragma once
+
+#define EXERCISM_RUN_ALL_TESTS
+
+
+namespace grains {
+
+typedef unsigned long long ulong_t;
+typedef unsigned int       index_t;
+
+ulong_t square(index_t index);
+ulong_t total();
+
+}