--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/SbpOperators/src/quadrature/inverse_diagonal_inner_product.jl	Fri Sep 25 14:11:00 2020 +0200
@@ -0,0 +1,36 @@
+export InverseDiagonalInnerProduct, closuresize
+"""
+    InverseDiagonalInnerProduct{Dim,T<:Real,M} <: TensorOperator{T,1}
+
+Implements the inverse diagonal inner product operator `Hi` of as a 1D TensorOperator
+"""
+struct InverseDiagonalInnerProduct{T<:Real,M} <: TensorOperator{T,1}
+    h_inv::T # The reciprocl grid spacing could be included in the stencil already. Preferable?
+    closure::NTuple{M,T}
+    #TODO: Write a nice constructor
+end
+
+function LazyTensors.apply(Hi::InverseDiagonalInnerProduct{T}, v::AbstractVector{T}, I::Index{Lower}) where T
+    return @inbounds Hi.h_inv*Hi.closure[Int(I)]*v[Int(I)]
+end
+
+function LazyTensors.apply(Hi::InverseDiagonalInnerProduct{T}, v::AbstractVector{T}, I::Index{Upper}) where T
+    N = length(v);
+    return @inbounds Hi.h_inv*Hi.closure[N-Int(I)+1]v[Int(I)]
+end
+
+function LazyTensors.apply(Hi::InverseDiagonalInnerProduct{T}, v::AbstractVector{T}, I::Index{Interior}) where T
+    return @inbounds Hi.h_inv*v[Int(I)]
+end
+
+function LazyTensors.apply(Hi::InverseDiagonalInnerProduct,  v::AbstractVector{T}, index::Index{Unknown}) where T
+    N = length(v);
+    r = getregion(Int(index), closuresize(Hi), N)
+    i = Index(Int(index), r)
+    return LazyTensors.apply(Hi, v, i)
+end
+
+LazyTensors.apply_transpose(Hi::InverseDiagonalInnerProduct{T}, v::AbstractVector{T}, I::Index) where T = LazyTensors.apply(Hi,v,I)
+
+
+closuresize(Hi::InverseDiagonalInnerProduct{T,M}) where {T,M} =  M