From b80db5274270dba4b6f92666528fee497c4f76bb Mon Sep 17 00:00:00 2001
From: kalmar <kalmar@amu.edu.pl>
Date: Tue, 11 Jul 2017 16:02:43 +0200
Subject: [PATCH] deepcopy result if result === X to prevent X from zeroing

---
 src/GroupRings.jl | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/GroupRings.jl b/src/GroupRings.jl
index 4d23d13..714b330 100644
--- a/src/GroupRings.jl
+++ b/src/GroupRings.jl
@@ -331,8 +331,11 @@ function mul!{T}(result::AbstractVector{T}, X::AbstractVector{T}, Y::AbstractVec
    end
 end
 
-function mul!(result::GroupRingElem, X::GroupRingElem, Y::GroupRingElem)
-   result.coeffs *= 0
+function mul!{T}(result::GroupRingElem{T}, X::GroupRingElem{T}, Y::GroupRingElem{T})
+   # @show result === X
+   if result === X
+      result = deepcopy(result)
+   end
    mul!(result.coeffs, X.coeffs, Y.coeffs, parent(X).pm)
    return result
 end