gens should return an independent copy

[kalmarek]

Slogan:

The modification of the result of gens(G) shall not modify the parent object.

[thofma]

Then there should be a function or a version of gens which does not copy :)

Maybe with a keyword argument a la gens(G, copy = false)?

[blegat]

Maybe gens could return an immutable version of the generator. E.g.

struct ImmutableVector{T, V}
    data::V
end
Base.iterate(...) = ...
Base.length(...) = ...
Base.push!(...) = error(...)
Base.setindex!(...) = error(...)