diff --git a/Project.toml b/Project.toml
index 2990148..89de0f1 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "ContinuumArrays"
 uuid = "7ae1f121-cc2c-504b-ac30-9b923412ae5c"
-version = "0.20.3"
+version = "0.20.4"
 
 [deps]
 AbstractFFTs = "621f4979-c628-5d54-868e-fcf4e3e8185c"
diff --git a/docs/src/index.md b/docs/src/index.md
index 27e814b..e685b7a 100644
--- a/docs/src/index.md
+++ b/docs/src/index.md
@@ -49,6 +49,9 @@ weaklaplacian
 
 ## Routines
 
+```@docs
+affine
+```
 ```@docs
 transform
 ```
diff --git a/src/ContinuumArrays.jl b/src/ContinuumArrays.jl
index 60332a3..6e9a147 100644
--- a/src/ContinuumArrays.jl
+++ b/src/ContinuumArrays.jl
@@ -3,7 +3,7 @@ using IntervalSets, DomainSets, LinearAlgebra, LazyArrays, FillArrays, BandedMat
 import Base: @_inline_meta, @_propagate_inbounds_meta, axes, size, getindex, convert, prod, *, /, \, +, -, ==, ^,
                 IndexStyle, IndexLinear, ==, OneTo, tail, similar, copyto!, copy, diff,
                 first, last, show, isempty, findfirst, findlast, findall, Slice, union, minimum, maximum, extrema, sum, _sum, _maximum, _minimum,
-                getproperty, isone, iszero, zero, abs, <, ≤, >, ≥, string, summary, to_indices, view, @propagate_inbounds
+                getproperty, isone, iszero, zero, abs, <, ≤, >, ≥, string, summary, to_indices, view, @propagate_inbounds, collect
 import Base.Broadcast: materialize, BroadcastStyle, broadcasted, Broadcasted
 import LazyArrays: MemoryLayout, Applied, ApplyStyle, flatten, _flatten, colsupport, combine_mul_styles, AbstractArrayApplyStyle,
                         adjointlayout, arguments, _mul_arguments, call, broadcastlayout, layout_getindex, UnknownLayout,
@@ -37,6 +37,7 @@ cardinality(::AbstractInterval) = ℵ₁
 cardinality(::Union{FullSpace{<:AbstractFloat},EuclideanDomain,DomainSets.RealNumbers,DomainSets.ComplexNumbers}) = ℵ₁
 cardinality(::Union{DomainSets.Integers,DomainSets.Rationals,DomainSets.NaturalNumbers}) = ℵ₀
 
+Inclusion(d::ProductDomain{T}) where T = Inclusion{float(T)}(d)
 Inclusion(d::AbstractInterval{T}) where T = Inclusion{float(T)}(d)
 first(S::Inclusion{<:Any,<:AbstractInterval}) = leftendpoint(S.domain)
 last(S::Inclusion{<:Any,<:AbstractInterval}) = rightendpoint(S.domain)
@@ -102,6 +103,10 @@ checkpoints(d::AbstractInterval{T}) where T = width(d) .* SVector{3,float(T)}(0.
 checkpoints(d::UnionDomain) = mapreduce(checkpoints,union,d.domains)
 checkpoints(x::Inclusion) = checkpoints(x.domain)
 checkpoints(A::AbstractQuasiMatrix) = checkpoints(axes(A,1))
+function checkpoints(P::ProductDomain)
+    x,y = map(checkpoints, components(P))
+    SVector.(x, y')
+end
 
 
 include("operators.jl")
diff --git a/src/bases/bases.jl b/src/bases/bases.jl
index a9a52c2..4e3d074 100644
--- a/src/bases/bases.jl
+++ b/src/bases/bases.jl
@@ -376,7 +376,9 @@ function expand(v)
 end
 
 
-
+expand(g::Base.Generator{<:Inclusion}) = expand(g.f.(g.iter))
+expand(g::Base.Generator{<:Domain}) = expand(Base.Generator(g.f, Inclusion(g.iter)))
+expand(g::Base.Generator{<:Base.Iterators.ProductIterator{<:Tuple{Vararg{Domain}}}}) = expand(Base.Generator(g.f, ×(g.iter.iterators...)))
 
 
 @inline copy(L::Ldiv{<:AbstractBasisLayout}) = basis_ldiv_size(size(L), L.A, L.B)
diff --git a/src/maps.jl b/src/maps.jl
index 2ca2efe..31d96a9 100644
--- a/src/maps.jl
+++ b/src/maps.jl
@@ -147,6 +147,13 @@ end
 first(A::AffineMap{T}) where T = convert(T, first(A.range))::T
 last(A::AffineMap{T}) where T = convert(T, last(A.range))::T
 
+"""
+    affine(a, b)
+
+constructs a quasivector corresponding to the affine map between two domains/quasivectors. For example:
+
+    affine(1..2, 2..3)[1.5] == 2.5
+"""
 affine(a::AbstractQuasiVector, b::AbstractQuasiVector) = AffineMap(a, b)
 affine(a, b::AbstractQuasiVector) = affine(Inclusion(a), b)
 affine(a::AbstractQuasiVector, b) = affine(a, Inclusion(b))
diff --git a/test/test_chebyshev.jl b/test/test_chebyshev.jl
index fc6298c..938570c 100644
--- a/test/test_chebyshev.jl
+++ b/test/test_chebyshev.jl
@@ -295,4 +295,9 @@ Base.:(==)(::FooBasis, ::FooBasis) = true
         @test_throws ErrorException maximum(exp.(x))
         @test_throws ErrorException minimum(exp.(x))
     end
+
+    @testset "generator" begin
+        @test expand(exp(t) for t in -1..1)[0.1] ≈ [exp(t) for t in -1..1][0.1] ≈ exp(0.1)
+        @test [exp(x*cos(y)) for x in Inclusion(0:0.5:1), y in Inclusion(1:0.5:2)][0.5,1.5] ≈ exp(0.5*cos(1.5))
+    end
 end