From b6576d7e276599af0517ebad42233047d753992e Mon Sep 17 00:00:00 2001
From: Mike Bosse <mike.bosse@mavt.ethz.ch>
Date: Thu, 4 Dec 2014 13:10:50 +0100
Subject: [PATCH] added group concept check

---
 GTSAM-Concepts.md     |  2 +-
 gtsam/base/concepts.h | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/GTSAM-Concepts.md b/GTSAM-Concepts.md
index 41bdafee9..774409e8d 100644
--- a/GTSAM-Concepts.md
+++ b/GTSAM-Concepts.md
@@ -162,7 +162,7 @@ The group composition operation can be of two flavors:
 * `gtsam::traits::additive_group_tag`
 * `gtsam::traits::multiplicative_group_tag`
 
-which should be queryable by `gtsam::traits::group_flavor<T>`
+which should be queryable by `gtsam::traits::group_flavor<T>::tag`
 
 
 Manifold Example
diff --git a/gtsam/base/concepts.h b/gtsam/base/concepts.h
index 05d7e378b..90f897b90 100644
--- a/gtsam/base/concepts.h
+++ b/gtsam/base/concepts.h
@@ -66,6 +66,29 @@ class ChartConcept {
 
 };
 
+template<class G>
+class GroupConcept {
+ public:
+  typedef G Group;
+  static const Group identity = traits::identity<G>::value;
+
+  BOOST_CONCEPT_USAGE(GroupConcept) {
+    Group ip = inverse(p);
+    Group pq = compose(p, q);
+    Group d = between(p, q);
+    bool test = equal(p, q);
+  }
+
+  bool check_invariants(const Group& a, const Group& b) {
+    return (equal(compose(a, inverse(a)), identity))
+        && (equal(between(a, b), compose(inverse(a), b)))
+        && (equal(compose(a, between(a, b)), b));
+  }
+
+ private:
+  Group p,q;
+};
+
 } // namespace gtsam
 
 #endif /* CONCEPTS_H_ */