Add state machine operators

Co-authored-by: Fredrik Bagge Carlson <[email protected]>

src/Symbolics.jl

@@ -146,6 +146,7 @@ export parse_expr_to_symbolic
 
 include("error_hints.jl")
 include("struct.jl")
+include("operators.jl")
 
 # Hacks to make wrappers "nicer"
 const NumberTypes = Union{AbstractFloat,Integer,Complex{<:AbstractFloat},Complex{<:Integer}}

src/operators.jl

@@ -0,0 +1,25 @@
+function activeState end
+function entry end
+function ticksInState end
+function timeInState end
+
+for (s, T) in [(:timeInState, :Real),
+               (:ticksInState, :Integer),
+               (:entry, :Bool),
+               (:activeState, :Bool)]
+    seed = hash(s)
+    @eval begin
+        $s(x) = wrap(term($s, x))
+        SymbolicUtils.promote_symtype(::typeof($s), _...) = $T
+        function SymbolicUtils.show_call(io, ::typeof($s), args)
+            if isempty(args)
+                print(io, $s, "()")
+            else
+                print(io, $s, "(", nameof(only(args)), ")")
+            end
+        end
+    end
+    if s != :activeState
+        @eval $s() = wrap(term($s))
+    end
+end