1 files changed, 29 insertions, 7 deletions
diff --git a/impl/VariableAssignment.hpp b/impl/VariableAssignment.hpp
index a1f0b5b..cfce925 100644
--- a/impl/VariableAssignment.hpp
+++ b/impl/VariableAssignment.hpp
@@ -8,6 +8,9 @@ template<typename Domain>
 struct VariableAssignment {
   virtual ~VariableAssignment() { }
   virtual const Domain& operator[](const Variable<Domain>&) const = 0;
+  virtual const Domain& operator[](const Variable<Domain>& x) {
+    return (*const_cast<const VariableAssignment*>(this))[x];
+  }
 };
 
 #include "EquationSystem.hpp"
@@ -19,21 +22,40 @@ template<typename Domain>
 struct DynamicVariableAssignment : public VariableAssignment<Domain> {
   DynamicVariableAssignment(
     const EquationSystem<Domain>& system,
-    const DynamicMaxStrategy<Domain>& strat
+    DynamicMaxStrategy<Domain>& strat,
+    const Domain& value=infinity<Domain>()
   ) : _system(system),
       _strategy(strat),
       _values(system.variableCount(), unknown(infinity<Domain>())),
       _stable(system.variableCount()),
       _influence(system.variableCount(),
-                 IdSet<Variable<Domain> >(system.variableCount()))
+                 IdSet<Variable<Domain> >(system.variableCount())),
+      _frozen(false)
   { }
 
+  void freeze() {
+    _frozen = true;
+  }
+
+  void thaw() {
+    _frozen = false;
+  }
+
+  bool is_frozen() {
+    return _frozen;
+  }
+
   const Domain& operator[](const Variable<Domain>& var) const {
-    solve(var);
     return _values[var];
   }
 
-  void invalidate(const Variable<Domain>& x) const {
+  const Domain& operator[](const Variable<Domain>& var) {
+    if (!_frozen)
+      solve(var);
+    return _values[var];
+  }
+
+  void invalidate(const Variable<Domain>& x) {
     log::fixpoint << indent() << "Invalidating " << x << std::endl;
     if (_stable.contains(x)) {
       _stable.remove(x);
@@ -56,7 +78,7 @@ struct DynamicVariableAssignment : public VariableAssignment<Domain> {
 
 private:
 
-  void solve(const Variable<Domain>& x) const {
+  void solve(const Variable<Domain>& x) {
     if (!_stable.contains(x)) {
       _stable.insert(x);
       log::fixpoint << indent() << "Stabilise " << x << std::endl;
@@ -93,7 +115,7 @@ private:
   }
 
   struct DependencyAssignment : public VariableAssignment<Domain> {
-    DependencyAssignment(const DynamicVariableAssignment& assignment, const Variable<Domain>& var)
+    DependencyAssignment(DynamicVariableAssignment& assignment, const Variable<Domain>& var)
       : _assignment(assignment), _var(var) { }
     const Domain& operator[](const Variable<Domain>& x) const {
       const Domain& result = _assignment[x];
@@ -101,7 +123,7 @@ private:
       return result;
     }
   private:
-    const DynamicVariableAssignment& _assignment;
+    DynamicVariableAssignment& _assignment;
     const Variable<Domain>& _var;
   };