JuliaCon Proceedings Review: Example fails

[ranocha]

I get

julia> using DelayDiffEq

julia> f(x, h, p, t) = -h(p, t - 1)
f (generic function with 1 method)

julia> h(p, t) = 1.0
h (generic function with 1 method)

julia> tspan = (0.0, 10.0)
(0.0, 10.0)

julia> lag(p, t) = 1.0
lag (generic function with 1 method)

julia> prob = DDEProblem(f, h, tspan; dependent_lags = (lag,))
DDEProblem with uType Float64 and tType Float64. In-place: false
timespan: (0.0, 10.0)
u0: 1.0

julia> sol = solve(prob, MethodOfSteps(Tsit5()))
ERROR: MethodError: no method matching lag(::Float64, ::SciMLBase.NullParameters, ::Float64)
An arithmetic operation was performed on a NullParameters object. This means no parameters were passed
into the AbstractSciMLProblem (e.x.: ODEProblem) but the parameters object `p` was used in an arithmetic
expression. Two common reasons for this issue are:

1. Forgetting to pass parameters into the problem constructor. For example, `ODEProblem(f,u0,tspan)` should
be `ODEProblem(f,u0,tspan,p)` in order to use parameters.

2. Using the wrong function signature. For example, with `ODEProblem`s the function signature is always
`f(du,u,p,t)` for the in-place form or `f(u,p,t)` for the out-of-place form. Note that the `p` argument
will always be in the function signature reguardless of if the problem is defined with parameters!

Closest candidates are:
  lag(::Any, ::Any)
   @ Main REPL[7]:1

Stacktrace:
  [1] discontinuity_function(integrator::DelayDiffEq.DDEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, SciMLBase.NullParameters, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, DDEProblem{Float64, Tuple{Float64, Float64}, Tuple{}, Tuple{typeof(lag)}, false, SciMLBase.NullParameters, DDEFunction{false, SciMLBase.FullSpecialize, typeof(f), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, typeof(SciMLBase.DEFAULT_OBSERVED), Nothing, Nothing}, typeof(h), Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardDDEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), DelayDiffEq.HistoryFunction{typeof(h), DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}}, LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DelayDiffEq.DDEStats, Nothing}, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), DelayDiffEq.HistoryFunction{typeof(h), DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}}, LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache, DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}, DelayDiffEq.FPSolver{NLFunctional{Rational{Int64}, Rational{Int64}}, false, Float64, DelayDiffEq.FPFunctionalConstantCache}, OrdinaryDiffEq.DEOptions{Float64, Float64, Float64, Float64, PIController{Float64}, typeof(DiffEqBase.ODE_DEFAULT_NORM), typeof(LinearAlgebra.opnorm), Nothing, CallbackSet{Tuple{}, Tuple{}}, typeof(DiffEqBase.ODE_DEFAULT_ISOUTOFDOMAIN), typeof(DiffEqBase.ODE_DEFAULT_PROG_MESSAGE), typeof(DiffEqBase.ODE_DEFAULT_UNSTABLE_CHECK), DataStructures.BinaryHeap{Float64, DataStructures.FasterForward}, DataStructures.BinaryHeap{Discontinuity{Float64, Int64}, DataStructures.FasterForward}, Nothing, Nothing, Int64, Tuple{}, Tuple{}, Tuple{}}, Float64, Int64, DelayDiffEq.HistoryFunction{typeof(h), DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}}, DataStructures.BinaryMinHeap{Float64}, DataStructures.BinaryMinHeap{Discontinuity{Float64, Int64}}, Float64, Float64, Nothing}, lag::typeof(lag), T::Float64, t::Float64)
    @ DelayDiffEq ~/.julia/packages/DelayDiffEq/o81Aq/src/track.jl:63
  [2] discontinuity_interval(integrator::DelayDiffEq.DDEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, SciMLBase.NullParameters, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, DDEProblem{Float64, Tuple{Float64, Float64}, Tuple{}, Tuple{typeof(lag)}, false, SciMLBase.NullParameters, DDEFunction{false, SciMLBase.FullSpecialize, typeof(f), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, typeof(SciMLBase.DEFAULT_OBSERVED), Nothing, Nothing}, typeof(h), Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardDDEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), DelayDiffEq.HistoryFunction{typeof(h), DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}}, LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DelayDiffEq.DDEStats, Nothing}, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), DelayDiffEq.HistoryFunction{typeof(h), DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}}, LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache, DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}, DelayDiffEq.FPSolver{NLFunctional{Rational{Int64}, Rational{Int64}}, false, Float64, DelayDiffEq.FPFunctionalConstantCache}, OrdinaryDiffEq.DEOptions{Float64, Float64, Float64, Float64, PIController{Float64}, typeof(DiffEqBase.ODE_DEFAULT_NORM), typeof(LinearAlgebra.opnorm), Nothing, CallbackSet{Tuple{}, Tuple{}}, typeof(DiffEqBase.ODE_DEFAULT_ISOUTOFDOMAIN), typeof(DiffEqBase.ODE_DEFAULT_PROG_MESSAGE), typeof(DiffEqBase.ODE_DEFAULT_UNSTABLE_CHECK), DataStructures.BinaryHeap{Float64, DataStructures.FasterForward}, DataStructures.BinaryHeap{Discontinuity{Float64, Int64}, DataStructures.FasterForward}, Nothing, Nothing, Int64, Tuple{}, Tuple{}, Tuple{}}, Float64, Int64, DelayDiffEq.HistoryFunction{typeof(h), DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}}, DataStructures.BinaryMinHeap{Float64}, DataStructures.BinaryMinHeap{Discontinuity{Float64, Int64}}, Float64, Float64, Nothing}, lag::Function, T::Float64, Θs::StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}, Int64})
    @ DelayDiffEq ~/.julia/packages/DelayDiffEq/o81Aq/src/track.jl:78
  [3] track_propagated_discontinuities!
    @ ~/.julia/packages/DelayDiffEq/o81Aq/src/track.jl:21 [inlined]
  [4] loopfooter!(integrator::DelayDiffEq.DDEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, SciMLBase.NullParameters, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, DDEProblem{Float64, Tuple{Float64, Float64}, Tuple{}, Tuple{typeof(lag)}, false, SciMLBase.NullParameters, DDEFunction{false, SciMLBase.FullSpecialize, typeof(f), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, typeof(SciMLBase.DEFAULT_OBSERVED), Nothing, Nothing}, typeof(h), Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardDDEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), DelayDiffEq.HistoryFunction{typeof(h), DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}}, LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DelayDiffEq.DDEStats, Nothing}, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), DelayDiffEq.HistoryFunction{typeof(h), DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}}, LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache, DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}, DelayDiffEq.FPSolver{NLFunctional{Rational{Int64}, Rational{Int64}}, false, Float64, DelayDiffEq.FPFunctionalConstantCache}, OrdinaryDiffEq.DEOptions{Float64, Float64, Float64, Float64, PIController{Float64}, typeof(DiffEqBase.ODE_DEFAULT_NORM), typeof(LinearAlgebra.opnorm), Nothing, CallbackSet{Tuple{}, Tuple{}}, typeof(DiffEqBase.ODE_DEFAULT_ISOUTOFDOMAIN), typeof(DiffEqBase.ODE_DEFAULT_PROG_MESSAGE), typeof(DiffEqBase.ODE_DEFAULT_UNSTABLE_CHECK), DataStructures.BinaryHeap{Float64, DataStructures.FasterForward}, DataStructures.BinaryHeap{Discontinuity{Float64, Int64}, DataStructures.FasterForward}, Nothing, Nothing, Int64, Tuple{}, Tuple{}, Tuple{}}, Float64, Int64, DelayDiffEq.HistoryFunction{typeof(h), DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}}, DataStructures.BinaryMinHeap{Float64}, DataStructures.BinaryMinHeap{Discontinuity{Float64, Int64}}, Float64, Float64, Nothing})
    @ DelayDiffEq ~/.julia/packages/DelayDiffEq/o81Aq/src/integrators/interface.jl:12
  [5] solve!(integrator::DelayDiffEq.DDEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, SciMLBase.NullParameters, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, DDEProblem{Float64, Tuple{Float64, Float64}, Tuple{}, Tuple{typeof(lag)}, false, SciMLBase.NullParameters, DDEFunction{false, SciMLBase.FullSpecialize, typeof(f), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, typeof(SciMLBase.DEFAULT_OBSERVED), Nothing, Nothing}, typeof(h), Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardDDEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), DelayDiffEq.HistoryFunction{typeof(h), DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}}, LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DelayDiffEq.DDEStats, Nothing}, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), DelayDiffEq.HistoryFunction{typeof(h), DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}}, LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache, DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}, DelayDiffEq.FPSolver{NLFunctional{Rational{Int64}, Rational{Int64}}, false, Float64, DelayDiffEq.FPFunctionalConstantCache}, OrdinaryDiffEq.DEOptions{Float64, Float64, Float64, Float64, PIController{Float64}, typeof(DiffEqBase.ODE_DEFAULT_NORM), typeof(LinearAlgebra.opnorm), Nothing, CallbackSet{Tuple{}, Tuple{}}, typeof(DiffEqBase.ODE_DEFAULT_ISOUTOFDOMAIN), typeof(DiffEqBase.ODE_DEFAULT_PROG_MESSAGE), typeof(DiffEqBase.ODE_DEFAULT_UNSTABLE_CHECK), DataStructures.BinaryHeap{Float64, DataStructures.FasterForward}, DataStructures.BinaryHeap{Discontinuity{Float64, Int64}, DataStructures.FasterForward}, Nothing, Nothing, Int64, Tuple{}, Tuple{}, Tuple{}}, Float64, Int64, DelayDiffEq.HistoryFunction{typeof(h), DelayDiffEq.HistoryODEIntegrator{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, false, Float64, Float64, Float64, Vector{Float64}, ODESolution{Float64, 1, Vector{Float64}, Nothing, Nothing, Vector{Float64}, Vector{Vector{Float64}}, ODEProblem{Float64, Tuple{Float64, Float64}, false, SciMLBase.NullParameters, DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardODEProblem}, Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, OrdinaryDiffEq.InterpolationData{DelayDiffEq.ODEFunctionWrapper{false, typeof(f), typeof(h), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing}, Vector{Float64}, Vector{Float64}, Vector{Vector{Float64}}, OrdinaryDiffEq.Tsit5ConstantCache}, DiffEqBase.Stats, Nothing}, OrdinaryDiffEq.Tsit5ConstantCache}}, DataStructures.BinaryMinHeap{Float64}, DataStructures.BinaryMinHeap{Discontinuity{Float64, Int64}}, Float64, Float64, Nothing})
    @ DelayDiffEq ~/.julia/packages/DelayDiffEq/o81Aq/src/solve.jl:431
  [6] #__solve#32
    @ ~/.julia/packages/DelayDiffEq/o81Aq/src/solve.jl:5 [inlined]
  [7] __solve
    @ ~/.julia/packages/DelayDiffEq/o81Aq/src/solve.jl:1 [inlined]
  [8] #solve_call#22
    @ ~/.julia/packages/DiffEqBase/ejpi7/src/solve.jl:509 [inlined]
  [9] solve_call
    @ ~/.julia/packages/DiffEqBase/ejpi7/src/solve.jl:479 [inlined]
 [10] #solve_up#29
    @ ~/.julia/packages/DiffEqBase/ejpi7/src/solve.jl:932 [inlined]
 [11] solve_up
    @ ~/.julia/packages/DiffEqBase/ejpi7/src/solve.jl:905 [inlined]
 [12] #solve#27
    @ ~/.julia/packages/DiffEqBase/ejpi7/src/solve.jl:842 [inlined]
 [13] solve(prob::DDEProblem{Float64, Tuple{Float64, Float64}, Tuple{}, Tuple{typeof(lag)}, false, SciMLBase.NullParameters, DDEFunction{false, SciMLBase.FullSpecialize, typeof(f), LinearAlgebra.UniformScaling{Bool}, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, typeof(SciMLBase.DEFAULT_OBSERVED), Nothing, Nothing}, typeof(h), Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, SciMLBase.StandardDDEProblem}, args::MethodOfSteps{Tsit5{typeof(OrdinaryDiffEq.trivial_limiter!), typeof(OrdinaryDiffEq.trivial_limiter!), Static.False}, NLFunctional{Rational{Int64}, Rational{Int64}}, false})
    @ DiffEqBase ~/.julia/packages/DiffEqBase/ejpi7/src/solve.jl:832
 [14] top-level scope
    @ REPL[9]:1

[devmotion]

Oops that's a typo: The syntax is lag(u, p, t) (see e.g. https://docs.sciml.ai/DiffEqDocs/stable/types/dde_types/#SciMLBase.DDEProblem).

julia> lag(u, p, t) = 1.0
lag (generic function with 2 methods)

julia> prob = DDEProblem(f, h, tspan; dependent_lags = (lag,))
DDEProblem with uType Float64 and tType Float64. In-place: false
timespan: (0.0, 10.0)
u0: 1.0

julia> sol = solve(prob, MethodOfSteps(Tsit5()))
retcode: Success
Interpolation: specialized 4th order "free" interpolation
t: 11-element Vector{Float64}:
  0.0
  1.0
  ⋮
  9.601646201268283
 10.0
u: 11-element Vector{Float64}:
 1.0
 2.220446049250313e-16
 ⋮
 0.03935344588087353
 0.019784973075655056

[ranocha]

Could you please update the paper accordingly?

[devmotion]

Fixed by https://github.com/SciML/DelayDiffEq.jl/commit/0dc1718c3f3fc4cc050e4c201438e739bde0cae9.