[bug#31430] [PATCH 1/3] gnu: Add json-modern-cxx.

[Fis Trivial]

* gnu/packages/cpp.scm (json-modern-cxx): New variable.
---
 gnu/packages/cpp.scm | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/gnu/packages/cpp.scm b/gnu/packages/cpp.scm
index 3e9c39df6..8a30d464e 100644
--- a/gnu/packages/cpp.scm
+++ b/gnu/packages/cpp.scm
@@ -124,3 +124,25 @@ unified access to TCP/UDP sockets, serial ports, console, 
and files streams.
 It also allows a server application to wait for any activity on any
 combination of these streams.")
     (license license:bsd-3)))
+
+(define-public json-modern-cxx
+  ;; The downloaded tar ball is about 109 MiB large, the most significant part
+  ;; comes from testing data file.
+  (package
+    (name "json-modern-cxx")
+    (version "3.1.2")
+    (source (origin
+              (method url-fetch)
+              (uri (string-append
+                    "https://github.com/nlohmann/json/archive/v";
+                    version ".tar.gz"))
+              (sha256
+               (base32
+                "0m5fhdpx2qll933db2nsi30nns3cifavzvijzz6mxhdkpmngmzz8"))
+              (file-name (string-append name "-" version ".tar.gz"))))
+    (home-page "https://github.com/nlohmann/json";)
+    (build-system cmake-build-system)
+    (synopsis "JSON for Modern C++")
+    (description "JSON for Modern C++ is a C++ json library that provides
+intutive syntax and trivial integration.")
+    (license license:expat)))
-- 
2.14.3