use Pre in the affect definition

Author: vyudu

src/ModelingToolkit.jl

@@ -270,6 +270,7 @@ export initialization_equations, guesses, defaults, parameter_dependencies, hier
 export structural_simplify, expand_connections, linearize, linearization_function,
        LinearizationProblem
 export solve
+export Pre
 
 export calculate_jacobian, generate_jacobian, generate_function, generate_custom_function
 export calculate_control_jacobian, generate_control_jacobian
@@ -302,7 +303,7 @@ export debug_system
 #export ContinuousClock, Discrete, sampletime, input_timedomain, output_timedomain
 #export has_discrete_domain, has_continuous_domain
 #export is_discrete_domain, is_continuous_domain, is_hybrid_domain
-export Sample, Hold, Shift, ShiftIndex, sampletime, SampleTime, Next, Prev
+export Sample, Hold, Shift, ShiftIndex, sampletime, SampleTime
 export Clock, SolverStepClock, TimeDomain
 
 export MTKParameters, reorder_dimension_by_tunables!, reorder_dimension_by_tunables

src/discretedomain.jl

@@ -70,19 +70,6 @@ Base.literal_pow(f::typeof(^), D::Shift, ::Val{n}) where {n} = Shift(D.t, D.step
 
 hasshift(eq::Equation) = hasshift(eq.lhs) || hasshift(eq.rhs)
 
-"""
-    Next(x)
-
-An alias for Shift(t, 1)(x).
-"""
-Next(x) = Shift(t, 1)(x)
-"""
-    Prev(x)
-
-An alias for Shift(t, -1)(x).
-"""
-Prev(x) = Shift(t, -1)(x)
-
 """
     hasshift(O)