gistfile1.txt

fun {Flatten Xs}
    case Xs
    of nil then nil
    [] X|Xr andthen {IsList X} then
        {Append {Flatten X} {Flatten Xr}}
    [] X|Xr then
        X|{Flatten Xr}
    end
end

fun {Flatten Xs}
    proc {FlattenD Xs E}
        case Xs
        of nil then E
        [] X|Xr andthen {IsList X} then
            {FlattenD X {FlattenD Xr E}}
        [] X|Xr then
            X|{FlattenD Xr E}
        end
    end
in {FlattenD Xs nil} end