[CP-SAT] improve doc on C++ builder API; rewrite python API to remove the DoubleLinearExpr class

examples/cpp/jobshop_sat.cc

@@ -106,7 +106,7 @@ int64_t ComputeHorizon(const JsspInputProblem& problem) {
 struct JobTaskData {
   IntervalVar interval;
   IntVar start;
-  IntVar duration;
+  LinearExpr duration;
   IntVar end;
 };
 
@@ -488,7 +488,8 @@ void CreateObjective(
       for (int a = 0; a < num_alternatives; ++a) {
         // Add cost if present.
         if (task.cost_size() > 0) {
-          objective_vars.push_back(job_task_to_alternatives[j][t][a].presence);
+          objective_vars.push_back(
+              IntVar(job_task_to_alternatives[j][t][a].presence));
           objective_coeffs.push_back(task.cost(a));
         }
       }
@@ -626,14 +627,13 @@ void AddMakespanRedundantConstraints(
   const int num_machines = problem.machines_size();
 
   // Global energetic reasoning.
-  std::vector<IntVar> all_task_durations;
+  LinearExpr sum_of_duration;
   for (const std::vector<JobTaskData>& tasks : job_to_tasks) {
     for (const JobTaskData& task : tasks) {
-      all_task_durations.push_back(task.duration);
+      sum_of_duration += task.duration;
     }
   }
-  cp_model.AddLessOrEqual(LinearExpr::Sum(all_task_durations),
-                          makespan * num_machines);
+  cp_model.AddLessOrEqual(sum_of_duration, makespan * num_machines);
 }
 
 void DisplayJobStatistics(
@@ -648,8 +648,7 @@ void DisplayJobStatistics(
   for (const std::vector<JobTaskData>& job : job_to_tasks) {
     num_tasks += job.size();
     for (const JobTaskData& task : job) {
-      if (task.duration.Proto().domain_size() != 2 ||
-          task.duration.Proto().domain(0) != task.duration.Proto().domain(1)) {
+      if (!task.duration.IsConstant()) {
         num_tasks_with_variable_duration++;
       }
     }

examples/cpp/network_routing_sat.cc

@@ -578,7 +578,7 @@ class NetworkRoutingSolver {
     // Node - Graph Constraint.
     for (int demand_index = 0; demand_index < num_demands; ++demand_index) {
       for (int arc = 0; arc < num_arcs; ++arc) {
-        path_vars[demand_index].push_back(cp_model.NewBoolVar());
+        path_vars[demand_index].push_back(IntVar(cp_model.NewBoolVar()));
       }
       // Fill Tuple Set for AllowedAssignment constraint.
       TableConstraint path_ct =

examples/cpp/shift_minimization_sat.cc

@@ -262,7 +262,7 @@ void LoadAndSolve(const std::string& file_name) {
     }
 
     // Check that we have not already visited this exact set of candidate jobs.
-    if (gtl::ContainsKey(visited_job_lists, intersecting_jobs)) continue;
+    if (visited_job_lists.contains(intersecting_jobs)) continue;
     visited_job_lists.insert(intersecting_jobs);
 
     // Collect the relevant worker job vars.

examples/cpp/sports_scheduling_sat.cc

@@ -107,14 +107,14 @@ void OpponentModel(int num_teams) {
     std::vector<IntVar> day_home_aways;
     for (int t = 0; t < num_teams; ++t) {
       day_opponents.push_back(opponents[t][d]);
-      day_home_aways.push_back(home_aways[t][d]);
+      day_home_aways.push_back(IntVar(home_aways[t][d]));
     }
 
     builder.AddInverseConstraint(day_opponents, day_opponents);
 
     for (int first_team = 0; first_team < num_teams; ++first_team) {
-      IntVar first_home = day_home_aways[first_team];
-      IntVar second_home = builder.NewBoolVar();
+      const IntVar first_home = IntVar(day_home_aways[first_team]);
+      const IntVar second_home = IntVar(builder.NewBoolVar());
       builder.AddVariableElement(day_opponents[first_team], day_home_aways,
                                  second_home);
       builder.AddEquality(first_home + second_home, 1);