diff --git a/Project.toml b/Project.toml
index dc2faec..cef11b8 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "Sobol"
 uuid = "ed01d8cd-4d21-5b2a-85b4-cc3bdc58bad4"
-version = "1.5.0"
+version = "2.0.0"
 
 [deps]
 DelimitedFiles = "8bb1440f-4735-579b-a4ab-409b98df4dab"
diff --git a/src/Sobol.jl b/src/Sobol.jl
index 2bbb87b..810d530 100644
--- a/src/Sobol.jl
+++ b/src/Sobol.jl
@@ -4,27 +4,27 @@ export SobolSeq, ScaledSobolSeq, next!
 
 include("soboldata.jl") #loads `sobol_a` and `sobol_minit`
 
-abstract type AbstractSobolSeq{N} end
+abstract type AbstractSobolSeq end
 
-# N iis the dimension of sequence being generated
-mutable struct SobolSeq{N} <: AbstractSobolSeq{N}
-    m::Array{UInt32,2} #array of size (sdim, 32)
-    x::Array{UInt32,1} #previous x = x_n, array of length sdim
-    b::Array{UInt32,1} #position of fixed point in x[i] is after bit b[i]
+mutable struct SobolSeq{X<:AbstractVector{UInt32}} <: AbstractSobolSeq
+    m::Matrix{UInt32} #array of size (sdim, 32)
+    x::X #previous x = x_n, array of length sdim
+    b::Vector{UInt32} #position of fixed point in x[i] is after bit b[i]
     n::UInt32 #number of x's generated so far
 end
 
-ndims(s::AbstractSobolSeq{N}) where {N} = N::Int
+Base.ndims(s::SobolSeq) = length(s.x)
 
-function SobolSeq(N::Int)
+function SobolSeq(x::AbstractVector{UInt32})
+    N = length(x)
     (N < 0 || N > (length(sobol_a) + 1)) && error("invalid Sobol dimension")
 
     m = ones(UInt32, (N, 32))
 
     #special cases
-    N == 0 && return(SobolSeq{0})(m,UInt32[],UInt32[],zero(UInt32))
+    N == 0 && return SobolSeq(m,UInt32[],x,zero(UInt32))
     #special cases 1
-    N == 1 && return(SobolSeq{N}(m,UInt32[0],UInt32[0],zero(UInt32)))
+    N == 1 && return SobolSeq(m,UInt32[0],fill!(x,zero(UInt32)),zero(UInt32))
 
     for i = 2:N
         a = sobol_a[i-1]
@@ -42,9 +42,9 @@ function SobolSeq(N::Int)
             end
         end
     end
-    SobolSeq{N}(m,zeros(UInt32,N),zeros(UInt32,N),zero(UInt32))
+    SobolSeq(m,zeros(UInt32,N),fill!(x,zero(UInt32)),zero(UInt32))
 end
-SobolSeq(N::Integer) = SobolSeq(Int(N))
+SobolSeq(N::Integer) = SobolSeq(Vector{UInt32}(undef, N))
 
 function next!(s::SobolSeq, x::AbstractVector{<:AbstractFloat})
     length(x) != ndims(s) && throw(BoundsError())
@@ -72,7 +72,7 @@ function next!(s::SobolSeq, x::AbstractVector{<:AbstractFloat})
     end
     return x
 end
-next!(s::SobolSeq) = next!(s, Array{Float64,1}(undef, ndims(s)))
+next!(s::SobolSeq) = next!(s, Vector{Float64}(undef, ndims(s)))
 
 # if we know in advance how many points (n) we want to compute, then
 # adopt a suggestion similar to the Joe and Kuo paper, which in turn
@@ -95,7 +95,7 @@ function skip!(s::SobolSeq, n::Integer, x; exact=false)
     for unused=1:nskip; next!(s,x); end
     return s
 end
-Base.skip(s::SobolSeq, n::Integer; exact=false) = skip!(s, n, Array{Float64,1}(undef, ndims(s)); exact=exact)
+Base.skip(s::SobolSeq, n::Integer; exact=false) = skip!(s, n, Vector{Float64}(undef, ndims(s)); exact=exact)
 
 function Base.show(io::IO, s::SobolSeq)
     print(io, "$(ndims(s))-dimensional Sobol sequence on [0,1]^$(ndims(s))")
@@ -115,20 +115,28 @@ Base.IteratorEltype(::Type{<:AbstractSobolSeq}) = Base.HasEltype()
 
 # Convenience wrapper for scaled Sobol sequences
 
-struct ScaledSobolSeq{N,T} <: AbstractSobolSeq{N}
-    s::SobolSeq{N}
-    lb::Vector{T}
-    ub::Vector{T}
-    function ScaledSobolSeq{N,T}(lb::Vector{T}, ub::Vector{T}) where {N,T}
-        length(lb)==length(ub)==N || throw(DimensionMismatch("lb and ub do not have length $N"))
-        new(SobolSeq(N), lb, ub)
+struct ScaledSobolSeq{T,X<:AbstractVector{UInt32},B<:AbstractVector{T}} <: AbstractSobolSeq
+    s::SobolSeq{X}
+    lb::B
+    ub::B
+    function ScaledSobolSeq(x::X, lb::B, ub::B) where {T,X<:AbstractVector{UInt32},B<:AbstractVector{T}}
+        length(x)==length(lb)==length(ub) || throw(DimensionMismatch("x, lb, and ub do not all have same length"))
+        new{T,X,B}(SobolSeq(x), lb, ub)
     end
 end
-function SobolSeq(N::Integer, lb, ub)
-    T = typeof(sum(ub) - sum(lb))
-    ScaledSobolSeq{Int(N),T}(copyto!(Vector{T}(undef,N), lb), copyto!(Vector{T}(undef,N), ub))
+function SobolSeq(x::AbstractVector{UInt32}, lb::B, ub::B) where {B}
+    if Base.IteratorEltype(B) === Base.HasEltype()
+        T = eltype(B)
+    else
+        i = iterate(lb)
+        isnothing(i) && error("Cannot determine eltype of empty iterator")
+        T = typeof(i[1])
+    end
+    ScaledSobolSeq(x, copyto!(Vector{T}(undef,length(x)), lb), copyto!(Vector{T}(undef, length(x)), ub))
 end
+SobolSeq(N::Integer, lb, ub) = SobolSeq(Vector{UInt32}(undef, N), lb, ub)
 SobolSeq(lb, ub) = SobolSeq(length(lb), lb, ub)
+Base.ndims(s::ScaledSobolSeq) = ndims(s.s)
 
 function next!(s::SobolSeq, x::AbstractVector{<:AbstractFloat},
                lb::AbstractVector, ub::AbstractVector)
@@ -139,22 +147,22 @@ function next!(s::SobolSeq, x::AbstractVector{<:AbstractFloat},
     end
     return x
 end
-function next!(s::SobolSeq{N}, lb::AbstractVector, ub::AbstractVector) where {N}
+function next!(s::SobolSeq, lb::AbstractVector, ub::AbstractVector)
     T = typeof(float((zero(eltype(ub)) - zero(eltype(lb)))))
-    next!(s, Vector{T}(undef, N), lb, ub)
+    next!(s, Vector{T}(undef, ndims(s)), lb, ub)
 end
 
 next!(s::ScaledSobolSeq, x::AbstractVector{<:AbstractFloat}) = next!(s.s, x, s.lb, s.ub)
-next!(s::ScaledSobolSeq{N,T}) where {N,T} = next!(s.s, Vector{float(T)}(undef, N), s.lb, s.ub)
-Base.eltype(::Type{ScaledSobolSeq{N,T}}) where {N,T} = Vector{float(T)}
+next!(s::ScaledSobolSeq{T}) where {T} = next!(s.s, Vector{float(T)}(undef, ndims(s)), s.lb, s.ub)
+Base.eltype(::Type{<:ScaledSobolSeq{T}}) where {T} = Vector{float(T)}
 
 Base.skip(s::ScaledSobolSeq, n; exact = false) = (skip(s.s, n; exact = exact); s)
 
-function Base.show(io::IO, s::ScaledSobolSeq{N,T}) where {N,T}
+function Base.show(io::IO, s::ScaledSobolSeq{T}) where {T}
     lb = s.lb; ub = s.ub
-    print(io, "$N-dimensional scaled $(float(T)) Sobol sequence on [$(lb[1]),$(ub[1])]")
+    print(io, "$(ndims(s))-dimensional scaled $(float(T)) Sobol sequence on [$(lb[1]),$(ub[1])]")
     cnt = 1
-    for i = 2:N
+    for i = 2:ndims(s)
         if lb[i] == lb[i-1] && ub[i] == ub[i-1]
             cnt += 1
         else
@@ -170,11 +178,11 @@ function Base.show(io::IO, s::ScaledSobolSeq{N,T}) where {N,T}
     end
 end
 
-function Base.show(io::IO, ::MIME"text/html", s::ScaledSobolSeq{N,T}) where {N,T}
+function Base.show(io::IO, ::MIME"text/html", s::ScaledSobolSeq{T}) where {T}
     lb = s.lb; ub = s.ub
-    print(io, "$N-dimensional scaled $(float(T)) Sobol sequence on [$(lb[1]),$(ub[1])]")
+    print(io, "$(ndims(s))-dimensional scaled $(float(T)) Sobol sequence on [$(lb[1]),$(ub[1])]")
     cnt = 1
-    for i = 2:N
+    for i = 2:ndims(s)
         if lb[i] == lb[i-1] && ub[i] == ub[i-1]
             cnt += 1
         else
diff --git a/test/runtests.jl b/test/runtests.jl
index 1555d98..a53b7be 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -16,7 +16,7 @@ using Sobol, Test
     for dim in dimensions
         println("Testing dimension $(dim)")
         open(joinpath(dirname(@__FILE__), "results", "exp_results_$(dim)")) do exp_results_file
-            s = SobolSeq(dim)
+            s = @inferred SobolSeq(dim)
             x = zeros(dim)
             for line in eachline(exp_results_file)
                 values = [parse(Float64, item) for item in split(line)]
@@ -40,13 +40,14 @@ end
     lb = [-1,0,0]
     ub = [1,3,2]
     N = length(lb)
-    s = SobolSeq(lb,ub)
-    @test s isa ScaledSobolSeq{3,Int}
+    s = @inferred SobolSeq(lb,ub)
+    @test s isa ScaledSobolSeq{Int} && ndims(s) == 3
     @test eltype(s) == Vector{Float64}
     @test eltype(SobolSeq(Float32.(lb),Float32.(ub))) == Vector{Float32}
     @test first(s) == [0,1.5,1]
     @test first(SobolSeq((x for x in lb), (x for x in ub))) == [0,1.5,1]
-    @test SobolSeq(N,lb,ub) isa ScaledSobolSeq{3,Int}
+    s = @inferred SobolSeq(N,lb,ub)
+    @test s isa ScaledSobolSeq{Int} && ndims(s) == 3
     @test_throws BoundsError SobolSeq(2,lb,ub)
 end