From 4e213c691df9f803dc365e80079ea274121967b5 Mon Sep 17 00:00:00 2001
From: kalmar <kalmar@amu.edu.pl>
Date: Tue, 11 Jul 2017 22:37:53 +0200
Subject: [PATCH] throw if dividing by a non-unit

---
 src/GroupRings.jl | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/GroupRings.jl b/src/GroupRings.jl
index b87b1ae..e2aa5ef 100644
--- a/src/GroupRings.jl
+++ b/src/GroupRings.jl
@@ -387,10 +387,12 @@ function divexact{T}(X::GroupRingElem{T}, Y::GroupRingElem{T})
    else
       idx = findfirst(Y)
       c = Y[idx]
+      c == 0 || throw("Can not invert")
       g = parent(Y).basis[idx]
       return X*1//c*parent(Y)(inv(g))
    end
 end
+
 ###############################################################################
 #
 #   *-involution