Update downstream_events.jl

Author: ChrisRackauckas

test/downstream/downstream_events.jl

@@ -8,11 +8,15 @@ end
 
 prob = ODEProblem(f,u0,tspan)
 
+function condition(u,t,integrator) # Event when event_f(u,t,k) == 0
+    u[1]
+end
+    
 affect! = nothingf =
 affect_neg! = function (integrator)
   integrator.u = ArrayPartition(SVector{1}(integrator.u[1]), SVector{1}(-integrator.u[2]))
 end
 
 callback = ContinuousCallback(condition,affect!,affect_neg!,interp_points=100)
 
-sol = solve(prob,Tsit5(),callback=callback,adaptive=false,dt=1/4)
+sol = solve(prob,Tsit5(),callback=callback,adaptive=false,dt=1/4)