#17 #18 New branch for extra-libs and first stab at adding abseil

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "abseil-cpp"]
+	path = abseil-cpp
+	url = git@github.com:abseil/abseil-cpp.git

CMakeLists.txt

@@ -61,6 +61,10 @@ target_include_directories(mylib PRIVATE tests)
 target_link_libraries(mytest PRIVATE mylib)
 add_test(test1 mytest)
 
+# configure abseil-cpp from submodule
+add_subdirectory(abseil-cpp)
+target_link_libraries(mylib PRIVATE absl::base absl::strings)
+
 # boost as a required dependency for mylib
 find_package(Boost REQUIRED)
 target_link_libraries(mylib PRIVATE "${Boost_LIBRARIES}")

src/MyLibrary.cpp

@@ -35,6 +35,10 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "Exception.hpp"
 
+#include <algorithm>
+
+#include <absl/strings/str_join.h>
+#include <absl/strings/str_split.h>
 #include <boost/math/special_functions/prime.hpp>
 
 namespace cpp_template {
@@ -55,4 +59,27 @@ int get_nth_prime(int n) {
   return static_cast<int>(boost::math::prime(static_cast<unsigned>(n)));
 }
 
+std::string rotate_substrings_left(
+	const std::string& original,
+	const std::string delimiter,
+	const long n) {
+
+  std::vector<absl::string_view> split = absl::StrSplit(original, delimiter);
+
+  if (split.size() < 2) {
+    return original;
+  }
+
+  const auto pivot = std::abs(n) % split.size();
+
+  if (n > 0) {
+    std::rotate(std::begin(split), std::begin(split) + pivot, std::end(split));
+  } else {
+    std::rotate(std::rbegin(split), std::rbegin(split) + pivot, std::rend(split));
+  }
+
+  return absl::StrJoin(split, delimiter);
+}
+
+
 } // namespace cpp_template

src/MyLibrary.hpp

@@ -34,8 +34,12 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #ifndef MYLIBRARY_H_
 #define MYLIBRARY_H_
 
+#include <string>
+
 namespace cpp_template {
 int get_nth_prime(int n);
+std::string rotate_substrings_left(
+	const std::string& original, std::string delimiter, long n);
 }
 
 #endif // MYLIBRARY_H_

tests/MyTests.cpp

@@ -56,3 +56,20 @@ TEST_CASE("correct out of range exceptions", "[primes]") {
   CHECK_THROWS_AS(get_nth_prime(-1), Exception);
   CHECK_THROWS_AS(get_nth_prime(std::numeric_limits<int>::max()), Exception);
 }
+
+// This tests the output of the `rotate_substrings_left` function
+TEST_CASE("correct strings are returned", "[substrings]") {
+  const std::string input = "a,b,c,d,e,f,g,h,i,j";
+
+  CHECK(rotate_substrings_left(input, ",", 0) == input);  // no rotation
+  CHECK(rotate_substrings_left(input, ",", 10) == input); // complete rotation left
+  CHECK(rotate_substrings_left(input, ",", -10) == input);  // complete rotation right
+
+  CHECK(rotate_substrings_left(input, ",", 1) == "b,c,d,e,f,g,h,i,j,a");  // one left
+  CHECK(rotate_substrings_left(input, ",", -1) == "j,a,b,c,d,e,f,g,h,i"); // one right
+  CHECK(rotate_substrings_left(rotate_substrings_left(input, ",", 1), ",", -1) == input);  // left then right
+  CHECK(rotate_substrings_left(rotate_substrings_left(input, ",", -1), ",", 1) == input);  // right then left
+
+  CHECK(rotate_substrings_left(input, ",", 15) == "f,g,h,i,j,a,b,c,d,e");  // 15 left (=5 left)
+  CHECK(rotate_substrings_left(input, ",", -13) == "h,i,j,a,b,c,d,e,f,g");  // 13 right (=3 right)
+}