Add unposting of new constraints on backtrack

src/solver/uniform_solver/uniform_solver.jl

@@ -154,8 +154,12 @@ function post!(solver::UniformSolver, constraint::AbstractLocalConstraint)
         return
     end
     #if the was not deactivated after initial propagation, it can be added to the list of constraints
-    @assert constraint ∉ keys(solver.isactive) "Attempted to post a constraint that was already posted before"
-    solver.isactive[constraint] = StateInt(solver.sm, 1)
+    if (constraint ∈ keys(solver.isactive))
+        @assert solver.isactive[constraint] == 0 "Attempted to post a constraint that is already active"
+    else
+        solver.isactive[constraint] = StateInt(solver.sm, 0) #initializing the state int as 0 will deactivate it on backtrack
+    end
+    set_value!(solver.isactive[constraint], 1)
 end
 
 

test/test_state_manager.jl

@@ -96,4 +96,13 @@
         @test get_value(a) == 10
         @test get_value(b) == 100
     end
+
+    @testset "behavior needed for constraint unposting" begin
+        sm = HerbConstraints.StateManager()
+        save_state!(sm)
+        a = StateInt(sm, 0)         # initialize a new state int, set its value to 0 (post a new constraint)
+        set_value!(a, 1)            # immediately update the state int to 1 (activate the newly posted constraint)
+        restore!(sm)            
+        @test get_value(a) == 0     # on backtrack, the new constraint should be deactivated
+    end
 end