format

Author: Brad Carman

src/Blocks/sources.jl

@@ -592,14 +592,14 @@ function set_sampled_data!(memory::Parameter{T}, t, x, Δt::Parameter{T}) where
     i = round(Int, t / Δt) + 1 #expensive
     if i == n + 1
         push!(memory.data, x)
-    elseif i<=n
+    elseif i <= n
         @inbounds memory.data[i] = x
     else
         error("Memory buffer skipped a step: n=$n, i=$i")
     end
 
     # memory.ref = Δt
-    
+
     return x
 end
 Symbolics.@register_symbolic set_sampled_data!(memory, t, x, Δt)
@@ -614,10 +614,8 @@ end
 Symbolics.derivative(::typeof(set_sampled_data!), args::NTuple{4, Any}, ::Val{3}) = 1
 
 function first_order_backwards_difference(t, x, Δt, memory)
-    
     x1 = set_sampled_data!(memory, t, x, Δt)
     x0 = get_sampled_data_const(t - Δt, memory)
 
     return (x1 - x0) / Δt
 end
-

test/Blocks/sources.jl

@@ -6,6 +6,7 @@ using ModelingToolkitStandardLibrary.Blocks: smooth_sin, smooth_cos, smooth_damp
 using OrdinaryDiffEq: ReturnCode.Success
 
 @parameters t
+D = Differential(t)
 
 @testset "Constant" begin
     @named src = Constant(k = 2)
@@ -413,11 +414,13 @@ end
     time = 0:dt:t_end
     x = @. time^2 + 1.0
 
+    vars = @variables y(t)=1 dy(t)=0
+
     @named src = SampledData(Float64)
     @named int = Integrator()
-    @named iosys = ODESystem([
-            connect(src.output, int.input),
-        ],
+    @named iosys = ODESystem([y ~ src.output.u
+            D(y) ~ dy
+            connect(src.output, int.input)],
         t,
         systems = [int, src])
     sys = structural_simplify(iosys)
@@ -432,4 +435,5 @@ end
 
     @test sol(time)[src.output.u]≈x atol=1e-3
     @test sol[int.output.u][end]≈1 / 3 * 10^3 + 10.0 atol=1e-3 # closed-form solution to integral
+    @test sol[dy][end]≈2 * time[end] atol=1e-3
 end