Convert GroupAlgebraElem to Dict

[lgoettgens]

The following code comes from the abandoned oscar-system/Oscar.jl#4334, and can be used to convert a GroupAlgebraElem (with sparse rep!) to a Dict{Group, elem_type(base_ring_type(...)) using Dict(x). I put this here in case someone wants to extend it for the dense rep and put it in the src.

function Base.length(x::GroupAlgebraElem)
  @assert Hecke._is_sparse(x)
  return length(x.coeffs_sparse)
end

function Base.iterate(x::GroupAlgebraElem)
  @assert Hecke._is_sparse(x)
  next = iterate(x.coeffs_sparse)
  isnothing(next) && return nothing
  (i, c), st = next
  return (parent(x).base_to_group[i], c), st
end

function Base.iterate(x::GroupAlgebraElem, st)
  @assert Hecke._is_sparse(x)
  next = iterate(x.coeffs_sparse, st)
  isnothing(next) && return nothing
  (i, c), st = next
  return (parent(x).base_to_group[i], c), st
end