From 9261df96ecc3c646e1d7c318b7c97301c80ad8b7 Mon Sep 17 00:00:00 2001
From: kalmarek <kalmar@amu.edu.pl>
Date: Tue, 4 Jun 2019 20:10:04 +0200
Subject: [PATCH] move Group Ring specific functions (norm, aug, supp, star) to
 misc.jl

---
 src/GroupRings.jl | 31 -------------------------------
 src/misc.jl       | 23 +++++++++++++++++++++++
 2 files changed, 23 insertions(+), 31 deletions(-)

diff --git a/src/GroupRings.jl b/src/GroupRings.jl
index 1db09a2..f93fee8 100644
--- a/src/GroupRings.jl
+++ b/src/GroupRings.jl
@@ -81,37 +81,6 @@ function (==)(A::GroupRing, B::GroupRing)
 end
 
 
-###############################################################################
-#
-#   *-involution
-#
-###############################################################################
-
-function star(X::GroupRingElem{T}) where T
-   RG = parent(X)
-   isdefined(RG, :basis) || throw("*-involution without basis is not possible")
-   result = RG(T)
-   for (i,c) in enumerate(X.coeffs)
-      if c != zero(T)
-         g = inv(RG.basis[i])
-         result[g] = c
-      end
-   end
-   return result
-end
-
-###############################################################################
-#
-#   Misc
-#
-###############################################################################
-
-LinearAlgebra.norm(X::GroupRingElem, p::Int=2) = norm(X.coeffs, p)
-
-aug(X::GroupRingElem) = sum(X.coeffs)
-
-supp(X::GroupRingElem) = parent(X).basis[findall(!iszero, X.coeffs)]
-
 function reverse_dict(::Type{I}, iter) where I<:Integer
    length(iter) > typemax(I) && error("Can not produce reverse dict: $(length(iter)) is too large for $T")
    return Dict{eltype(iter), I}(x => i for (i,x) in enumerate(iter))
diff --git a/src/misc.jl b/src/misc.jl
index bdcceda..97adaa4 100644
--- a/src/misc.jl
+++ b/src/misc.jl
@@ -53,3 +53,26 @@ Base.@propagate_inbounds function Base.setindex!(X::GroupRingElem, val,  g::Grou
     return X.coeffs[RG[g]] = val
 end
 
+###############################################################################
+#
+#   GroupRing specifics: augmentation, support, *-involution
+#
+###############################################################################
+
+aug(X::GroupRingElem) = sum(X.coeffs)
+
+function supp(X::GroupRingElem)
+    @assert hasbasis(parent(X))
+    dropzeros!(X.coeffs)
+    return parent(X).basis[X.coeffs.nzind]
+end
+
+function star(X::GroupRingElem{T}) where T
+    RG = parent(X)
+    hasbasis(RG) || throw(ArgumentError("*-involution without basis is not possible"))
+    nzind = [RG.basis_dict[inv(RG.basis[i])] for i in X.coeffs.nzind]
+    return GroupRingElem(sparsevec(nzind, X.coeffs.nzval, X.coeffs.n), RG)
+end
+
+LinearAlgebra.norm(X::GroupRingElem, p::Int=2) = norm(X.coeffs, p)
+