add perm action from the right (by inverse) on MatElems

groups/speciallinear.jl

@@ -87,6 +87,24 @@ function (g::WreathProductElem)(A::MatElem)
     return Nemo.mul!(res, M(G), res)
 end
 
+import Base.*
+
+doc"""
+    *(x::AbstractAlgebra.MatElem, P::Generic.perm)
+> Apply the pemutation $P$ to the rows of the matrix $x$ and return the result.
+"""
+function *(x::AbstractAlgebra.MatElem, P::Generic.perm)
+   z = similar(x)
+   m = rows(x)
+   n = cols(x)
+   for i = 1:m
+      for j = 1:n
+         z[i, j] = x[i, P[j]]
+      end
+   end
+   return z
+end
+
 function (p::perm)(A::MatElem)
     length(p.d) == A.r == A.c || throw("Can't act via $p on matrix of size ($(A.r), $(A.c))")
     return p*A*inv(p)