gnu: Add ocaml-react.

* gnu/packages/ocaml.scm (ocaml-react): New variable.

gnu/packages/ocaml.scm

@@ -1335,3 +1335,29 @@ (define-public ocaml-ppx-tools
     (synopsis "Tools for authors of ppx rewriters and other syntactic tools")
     (description "Tools for authors of ppx rewriters and other syntactic tools.")
     (license license:expat)))
+
+(define-public ocaml-react
+  (package
+    (name "ocaml-react")
+    (version "1.2.0")
+    (source
+      (origin
+        (method url-fetch)
+        (uri (string-append "http://erratique.ch/software/react/releases/react-"
+                            version ".tbz"))
+        (sha256 (base32
+                  "0knhgbngphv5sp1yskfd97crf169qhpc0igr6w7vqw0q36lswyl8"))))
+    (build-system ocaml-build-system)
+    (native-inputs `(("opam" ,opam)))
+    (arguments `(#:tests? #f
+                 #:build-flags (list "native=true" "native-dynlink=true")
+                 #:phases
+                 (modify-phases %standard-phases
+                   (delete 'configure))))
+    (home-page "http://erratique.ch/software/react")
+    (synopsis "Declarative events and signals for OCaml")
+    (description "React is an OCaml module for functional reactive programming
+(FRP).  It provides support to program with time varying values: declarative
+events and signals.  React doesn't define any primitive event or signal, it
+lets the client choose the concrete timeline.")
+    (license license:bsd-3)))