gnu: Add nlohmann-json-cpp.

* gnu/packages/serialization.scm (nlohmann-json-cpp): New variable.

Signed-off-by: Leo Famulari <leo@famulari.name>

gnu/packages/serialization.scm

@@ -5,6 +5,7 @@
 ;;; Copyright © 2016 Marius Bakke <mbakke@fastmail.com>
 ;;; Copyright © 2016 Efraim Flashner <efraim@flashner.co.il>
 ;;; Copyright © 2017 Corentin Bocquillon <corentin@nybble.fr>
+;;; Copyright © 2017 Gregor Giesen <giesen@zaehlwerk.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -328,3 +329,25 @@ (define-public libbson
 convert JSON documents to BSON and the opposite.  BSON stands for Binary JSON,
 it is comparable to protobuf.")
     (license license:asl2.0)))
+
+(define-public nlohmann-json-cpp
+  (package
+    (name "nlohmann-json-cpp")
+    (version "2.1.1")
+    (source
+     (origin
+      (method url-fetch)
+      (uri (string-append "https://github.com/nlohmann/json/"
+                          "archive/v" version ".tar.gz"))
+      (file-name (string-append name "-" version ".tar.gz"))
+      (sha256
+       (base32
+        "0lrh6cjd643c7kmvmwafbgq7dqj3b778483gjhjbvp6rc6z5xf2r"))))
+    (build-system cmake-build-system)
+    (home-page "https://nlohmann.github.io/json/")
+    (synopsis "JSON library for C++")
+    (description
+     "JSON library for C++ trying to accomplish “Intuitive syntax”,
+“Trivial integration”, and “Serious testing”.
+However, “Memory efficiency” and “Speed” have not been primary goals.")
+    (license license:expat)))