some more thinking...

planner/src/rules.rs

@@ -19,14 +19,34 @@
 //! Price
 //! - Per week : should restrict ingredients cost to a given amount
 
-trait Rule {
-    type State;
+enum Status {
+    Ok,
+    Violated,
+}
 
-    fn check(&self, state: Self::State);
-    fn insights(&self, state: Self::State) -> Insight;
+trait Rule {
+    type Key;
+    type Value;
+
+    fn status(&self, state: (Vec<&Self::Key>, Vec<&Self::Value>));
+    fn update(&self, idx: usize, value: Option<Self::Value>) -> Option<Filter>;
 };
 
 struct AllDifferentMeals;
+
+impl Rule for AllDifferentMeals {
+    type State = Vec<Recipe>;
+
+    fn status(&self, _: Self::State) -> Status {
+        Status::Ok // Always enforced by update rule
+    }
+
+    fn update(&self, _: Self::State) -> Option<Filter> {
+        // Returns a filter excluding this value from domain.
+        // so that it is impossible to select the same meal twice.
+        None
+    }
+}
 struct FilterRecipeByMeals; // Essentially work on domain
 
 struct NutritionalByDayAverageReq;

planner/src/solver.rs

@@ -180,6 +180,8 @@ impl<'p, V: PartialEq, K: Eq + Hash + Clone> Problem<'p, V, K> {
     /// a Clear to ensure the variable is unset before when leaving the branch.
     fn _push_updates(&self) -> Option<Vec<Assignment<'p,V>>> {
         if let Some(idx) = self._next_assign() {
+            // TODO: Domain will filter possible values for us
+            // let values = self.domain.get(idx);
             let domain_values = self.domains
                                     .get(idx)
                                     .expect("No domain for variable !");
@@ -187,7 +189,6 @@ impl<'p, V: PartialEq, K: Eq + Hash + Clone> Problem<'p, V, K> {
             assert!(!domain_values.is_empty());
             // Push a clear assignment first, just before going up the stack.
             let mut updates = vec![Assignment::Clear(idx.clone())];
-            // TODO: should be able to filter domain values (inference, pertinence)
             domain_values.iter().for_each(|value| {
                 updates.push(
                     Assignment::Update(idx, *value)
@@ -233,14 +234,14 @@ impl<'p, V: PartialEq, K: Eq + Hash + Clone> Problem<'p, V, K> {
     fn _assign(&mut self, idx: usize, value: Option<&'p V>) {
         self.variables[idx] = value;
         let var_key = &self.keys[idx];
+        // TODO: manage dynamic filters on Domain
+        // let filters: Filter::Chain = self.constraints.iter_mut().map([...]).collect();
+        // self.domain.set_global(idx, filters);
         self.constraints.iter_mut()
                         .for_each(|c| {
                             c.update(&var_key, value);
                         });
-        // Some thoughts: what if we used a stack of filters,
-        // for each variable, that is cleared, on every assign,
-        // and repopulated by aggregating update calls on constraints.
-        // Domain would then be filtered by ALL filters in these stacks.
+
     }
 
     fn _solve(&mut self, limit: Option<usize>) -> Vec<Solution<'p, V, K>> {