From 2c5e4fe2053aa3a309161f9200661692c17ac6bf Mon Sep 17 00:00:00 2001
From: Tommy Hofmann <thofma@gmail.com>
Date: Fri, 24 Aug 2018 15:16:43 +0200
Subject: [PATCH] Add support for empty FacElem

---
 src/Misc/FactoredElem.jl   | 10 ++++++++++
 src/NfOrd/FacElem.jl       |  3 +++
 src/NfOrd/Ideal/FacElem.jl |  3 +++
 3 files changed, 16 insertions(+)

diff --git a/src/Misc/FactoredElem.jl b/src/Misc/FactoredElem.jl
index 0e8ffb5283..6d5a1d7c5b 100644
--- a/src/Misc/FactoredElem.jl
+++ b/src/Misc/FactoredElem.jl
@@ -61,6 +61,13 @@ function FacElem(d::Dict{B, fmpz}) where B
   return z
 end
 
+function FacElem(R::Ring)
+  z = FacElem{elem_type(R), typeof(R)}()
+  z.fac = Dict{elem_type(R), fmpz}()
+  z.parent = FacElemMon(R)
+  return z
+end
+
 function FacElem(d::Dict{B, T}) where {B, T <: Integer}
 
   length(d) == 0 && error("Dictionary must not be empty")
@@ -450,6 +457,9 @@ function simplify!(x::FacElem{fmpq})
 end
 
 function simplify!(x::FacElem{fmpz})
+  if length(x.fac) < 1
+    return x
+  end
   if length(x.fac) <= 1
     k,v = first(x.fac)
     if isone(k)
diff --git a/src/NfOrd/FacElem.jl b/src/NfOrd/FacElem.jl
index 0ba2e8a959..37a6f31fc5 100644
--- a/src/NfOrd/FacElem.jl
+++ b/src/NfOrd/FacElem.jl
@@ -122,6 +122,9 @@ function factored_norm(x::FacElem{nf_elem})
       push!(c, -e)
     end
   end
+  if length(b) == 0
+    return FacElem(FlintZZ)
+  end
   f = FacElem(b, c)
   simplify!(f)
   return f
diff --git a/src/NfOrd/Ideal/FacElem.jl b/src/NfOrd/Ideal/FacElem.jl
index 225544e603..63d6faa634 100644
--- a/src/NfOrd/Ideal/FacElem.jl
+++ b/src/NfOrd/Ideal/FacElem.jl
@@ -60,6 +60,9 @@ function abs(A::FacElemQ)
       B[ak] = v
     end
   end
+  if length(B) == 0
+    return FacElem(FlintZZ)
+  end
   return FacElem(B)
 end