`zero!(Vector{<:RingElement})`

[thofma]

Spent an hour looking for a bug, which turned out to be coming from a line of the form

zero!(A)

where A::Vector{ZZRingElem}. This will call zero(parent(A)), which surprisingly does not fail, since parent(A) === A, and then it calls map(zero, A).

Are there objections to doing something of the form

function zero!(A::Vector{T}) where {T <: RingElement}
  for i in 1:length(A)
    A[i] = zero!(A[i])
  end
  return A
end

?

[fingolfin]

Seems fine to me, go for it.

[mjrodgers]

Would it make sense to do for i in eachindex(A)? Then this could apply to Array{T} instead of just to Vector

[JohnAAbbott]

Perhaps also a variant for {T <: MatElem}? Note that MatRingElem is already covered by the proposal above.