Merge pull request #2441 from SciML/myb/state_machine

Add StateMachineOperators

Author: YingboMa

src/ModelingToolkit.jl

@@ -55,7 +55,9 @@ using PrecompileTools, Reexport
     using Symbolics: _parse_vars, value, @derivatives, get_variables,
                      exprs_occur_in, solve_for, build_expr, unwrap, wrap,
                      VariableSource, getname, variable, Connection, connect,
-                     NAMESPACE_SEPARATOR, set_scalar_metadata, setdefaultval
+                     NAMESPACE_SEPARATOR, set_scalar_metadata, setdefaultval,
+                     initial_state, transition, activeState, entry,
+                     ticksInState, timeInState
     import Symbolics: rename, get_variables!, _solve, hessian_sparsity,
                       jacobian_sparsity, isaffine, islinear, _iszero, _isone,
                       tosymbol, lower_varname, diff2term, var_from_nested_derivative,
@@ -219,6 +221,7 @@ export JumpProblem
 export NonlinearSystem, OptimizationSystem, ConstraintsSystem
 export alias_elimination, flatten
 export connect, domain_connect, @connector, Connection, Flow, Stream, instream
+export initial_state, transition, activeState, entry, ticksInState, timeInState
 export @component, @mtkmodel, @mtkbuild
 export isinput, isoutput, getbounds, hasbounds, getguess, hasguess, isdisturbance,
        istunable, getdist, hasdist,

src/systems/connectors.jl

@@ -1,3 +1,6 @@
+using Symbolics: StateMachineOperator
+isconnection(_) = false
+isconnection(_::Connection) = true
 """
     domain_connect(sys1, sys2, syss...)
 
@@ -327,17 +330,17 @@ function generate_connection_set!(connectionsets, domain_csets,
             end
             neweq isa AbstractArray ? append!(eqs, neweq) : push!(eqs, neweq)
         else
-            if lhs isa Number || lhs isa Symbolic || eltype(lhs) <: Symbolic
+            if lhs isa Connection && get_systems(lhs) === :domain
+                connection2set!(domain_csets, namespace, get_systems(rhs), isouter)
+            elseif isconnection(rhs)
+                push!(cts, get_systems(rhs))
+            else
                 # split connections and equations
                 if eq.lhs isa AbstractArray || eq.rhs isa AbstractArray
                     append!(eqs, Symbolics.scalarize(eq))
                 else
                     push!(eqs, eq)
                 end
-            elseif lhs isa Connection && get_systems(lhs) === :domain
-                connection2set!(domain_csets, namespace, get_systems(rhs), isouter)
-            else
-                push!(cts, get_systems(rhs))
             end
         end
     end