diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1a275ad1..cf4cdf4d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -451,6 +451,7 @@ if (TESTS)
         bitwise
         cmdopt
         colour
+        comparator
         coord
         crypto/arc4
         crypto/ice
diff --git a/test/comparator.cpp b/test/comparator.cpp
new file mode 100644
index 00000000..c163f2dc
--- /dev/null
+++ b/test/comparator.cpp
@@ -0,0 +1,24 @@
+#include "tap.hpp"
+
+#include "types/comparator.hpp"
+
+int
+main (int, char**)
+{
+    util::TAP::logger tap;
+
+    const auto a = { 1, 2, 3 };
+    const auto b = { 1, 2, 4 };
+
+    tap.expect (
+        util::comparator::indexed<decltype(a)> ()(a, b),
+        "compare initializer_list as a coordinate, success"
+    );
+
+    tap.expect (
+        !util::comparator::indexed<decltype(a)> ()(b, a),
+        "compare initializer_list as a coordinate, failure"
+    );
+
+    return tap.status ();
+}
\ No newline at end of file
diff --git a/types/comparator.hpp b/types/comparator.hpp
index deb39eb1..934bd970 100644
--- a/types/comparator.hpp
+++ b/types/comparator.hpp
@@ -11,7 +11,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
- * Copyright 2012 Danny Robson <danny@nerdcruft.net>
+ * Copyright 2012-2017 Danny Robson <danny@nerdcruft.net>
  */
 
 #ifndef __UTIL_TYPES_COMPARATOR_HPP
@@ -19,14 +19,41 @@
 
 #include <memory>
 
-namespace util {
+#include "./iterator.hpp"
+
+namespace util::comparator {
     template <typename T>
     struct pointer_comparator {
         bool operator() (const std::unique_ptr<T> &lhs, const std::unique_ptr<T> &rhs);
         bool operator() (const T                  *lhs, const std::unique_ptr<T> &rhs);
         bool operator() (const std::unique_ptr<T> &lhs, const T                  *rhs);
     };
+
+
+    ///////////////////////////////////////////////////////////////////////////
+    /// Provides a comparison interface for types exposing an index operator.
+    ///
+    /// Will return true if the first parameter has the first index that
+    /// compares less than the second parameter. Useful for providing a total
+    /// order of coordinate types where this doesn't make sense by default.
+    ///
+    /// \tparam T The container data type to compare. Must provide an index
+    /// operator.
+    template <typename T>
+    struct indexed {
+        constexpr
+        bool operator() (const T &a, const T &b)
+        {
+            for (auto x: util::zip (a, b)) {
+                const auto &[i,j] = x; // clang-4.0: workaround for segfault.
+                if (i  < j) return true;
+                if (i != j) return false;
+            }
+
+            return false;
+        }
+    };
 }
 
-#include "util/types/comparator.ipp"
+#include "./comparator.ipp"
 #endif
diff --git a/types/comparator.ipp b/types/comparator.ipp
index 86d6020a..f9a52ee2 100644
--- a/types/comparator.ipp
+++ b/types/comparator.ipp
@@ -11,7 +11,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
- * Copyright 2012 Danny Robson <danny@nerdcruft.net>
+ * Copyright 2012-2017 Danny Robson <danny@nerdcruft.net>
  */
 
 #ifdef __UTIL_TYPES_COMPARATOR_IPP
@@ -22,7 +22,7 @@
 
 
 //-----------------------------------------------------------------------------
-namespace util {
+namespace util::comparator {
     template <typename T>
     bool
     pointer_comparator<T>::operator() (const std::unique_ptr<T> &lhs,