Hello, I have tried to use your package.

But I run into an error for reproducing your demo, I got:

```
using SparseVolterraExamples
using IntervalSets
K(x, y) = 1 - exp(x)
f(x) = 3x^3
ffun = Fun(x->f(x), Jacobi(0,1,0..1))
N = 50
u = triVolterraEQ2FullKernelSolver(ffun,K,N,true)
plot(u, legend=false)
```

```
Output exceeds the size limit. Open the full output data in a text editor
UndefVarError: _isless not defined
Stacktrace:
[1] getproperty
@ ./Base.jl:31 [inlined]
[2] isless
@ ~/.julia/packages/BlockArrays/8a1Kg/src/blockindices.jl:71 [inlined]
[3] <(x::Block{1, Int64}, y::Block{1, Int64})
@ Base ./operators.jl:356
[4] >(x::Block{1, Int64}, y::Block{1, Int64})
@ Base ./operators.jl:382
[5] BandedBlockBandedMatrix(V::ApproxFunBase.SubOperator{Float64, TimesOperator{Float64, Tuple{InfiniteArrays.Infinity, InfiniteArrays.Infinity}}, Tuple{BlockArrays.BlockRange{1, Tuple{UnitRange{Int64}}}, BlockArrays.BlockRange{1, Tuple{UnitRange{Int64}}}}, Tuple{Int64, Int64}, Tuple{Int64, Int64}})
@ ApproxFunBase ~/.julia/packages/ApproxFunBase/92sMu/src/Operators/general/algebra.jl:487
[6] (AbstractMatrix)(V::ApproxFunBase.SubOperator{Float64, TimesOperator{Float64, Tuple{InfiniteArrays.Infinity, InfiniteArrays.Infinity}}, Tuple{BlockArrays.BlockRange{1, Tuple{UnitRange{Int64}}}, BlockArrays.BlockRange{1, Tuple{UnitRange{Int64}}}}, Tuple{Int64, Int64}, Tuple{Int64, Int64}})
@ ApproxFunBase ~/.julia/packages/ApproxFunBase/92sMu/src/Operators/Operator.jl:781
[7] defaultgetindex(B::TimesOperator{Float64, Tuple{InfiniteArrays.Infinity, InfiniteArrays.Infinity}}, k::BlockArrays.BlockRange{1, Tuple{UnitRange{Int64}}}, j::BlockArrays.BlockRange{1, Tuple{UnitRange{Int64}}})
@ ApproxFunBase ~/.julia/packages/ApproxFunBase/92sMu/src/Operators/Operator.jl:234
[8] getindex(B::TimesOperator{Float64, Tuple{InfiniteArrays.Infinity, InfiniteArrays.Infinity}}, k::BlockArrays.BlockRange{1, Tuple{UnitRange{Int64}}}, j::BlockArrays.BlockRange{1, Tuple{UnitRange{Int64}}})
@ ApproxFunBase ~/.julia/packages/ApproxFunBase/92sMu/src/Operators/Operator.jl:208
[9] plan_evaluate(::Fun{JacobiTriangle, Float64, Vector{Float64}})
@ MultivariateOrthogonalPolynomials ~/.julia/packages/MultivariateOrthogonalPolynomials/kZS4T/src/Triangle/Triangle.jl:422
[10] evaluate(f::Vector{Float64}, K::JacobiTriangle, x::StaticArrays.SVector{2, Float64})
@ MultivariateOrthogonalPolynomials ~/.julia/packages/MultivariateOrthogonalPolynomials/kZS4T/src/Triangle/Triangle.jl:433
[11] evaluate
@ ~/.julia/packages/ApproxFunBase/92sMu/src/Fun.jl:216 [inlined]
...
@ SparseVolterraExamples ~/SparseVolterraExamples/src/triVolterraFullKernel.jl:86
[22] triVolterraEQ2FullKernelSolver(g::Fun{Jacobi{ClosedInterval{Int64}, Float64}, Float64, Vector{Float64}}, Kfun::Function, depth::Int64, flip::Bool)
@ SparseVolterraExamples ~/SparseVolterraExamples/src/triVolterraFullKernel.jl:36
[23] top-level scope
```