diff --git a/apps/calculation/app.cpp b/apps/calculation/app.cpp
index 48a60cb8d..51b521e66 100644
--- a/apps/calculation/app.cpp
+++ b/apps/calculation/app.cpp
@@ -91,14 +91,13 @@ bool App::textInputIsCorrect(const char * text) {
   /* Here, we check that the expression entered by the user can be printed with
    * less than k_printedExpressionLength characters. Otherwise, we prevent the
    * user from adding this expression to the calculation store. */
-  Expression * exp = Expression::parse(text);
-  if (exp == nullptr) {
+  Expression exp = Expression::parse(text);
+  if (!exp.isDefined()) {
     return false;
   }
-  Expression::ReplaceSymbolWithExpression(&exp, Symbol::SpecialSymbols::Ans, static_cast<Snapshot *>(snapshot())->calculationStore()->ansExpression(localContext()));
+  exp = exp.replaceSymbolWithExpression(Symbol::SpecialSymbols::Ans, static_cast<Snapshot *>(snapshot())->calculationStore()->ansExpression(localContext()));
   char buffer[Calculation::k_printedExpressionSize];
   int length = PoincareHelpers::Serialize(exp, buffer, sizeof(buffer));
-  delete exp;
   /* if the buffer is totally full, it is VERY likely that writeTextInBuffer
    * escaped before printing utterly the expression. */
   if (length >= Calculation::k_printedExpressionSize-1) {
diff --git a/apps/calculation/calculation.cpp b/apps/calculation/calculation.cpp
index 02da02862..2b9cf58ed 100644
--- a/apps/calculation/calculation.cpp
+++ b/apps/calculation/calculation.cpp
@@ -39,10 +39,9 @@ void Calculation::reset() {
   tidy();
 }
 
-void Calculation::setContent(const char * c, Context * context, Expression * ansExpression) {
+void Calculation::setContent(const char * c, Context * context, Expression ansExpression) {
   reset();
-  m_input = Expression::parse(c);
-  Expression::ReplaceSymbolWithExpression(&m_input, Symbol::SpecialSymbols::Ans, ansExpression);
+  m_input = Expression::parse(c).replaceSymbolWithExpression(Symbol::SpecialSymbols::Ans, ansExpression);
   /* We do not store directly the text enter by the user because we do not want
    * to keep Ans symbol in the calculation store. */
   PoincareHelpers::Serialize(m_input, m_inputText, sizeof(m_inputText));
@@ -143,7 +142,7 @@ void Calculation::tidy() {
   m_equalSign = EqualSign::Unknown;
 }
 
-Expression * Calculation::exactOutput(Context * context) {
+Expression Calculation::exactOutput(Context * context) {
   if (!m_exactOutput.isDefined()) {
     /* Because the angle unit might have changed, we do not simplify again. We
      * thereby avoid turning cos(Pi/4) into sqrt(2)/2 and displaying
@@ -161,7 +160,7 @@ LayoutRef Calculation::createExactOutputLayout(Context * context) {
   return PoincareHelpers::CreateLayout(exactOutput(context));
 }
 
-Expression * Calculation::approximateOutput(Context * context) {
+Expression Calculation::approximateOutput(Context * context) {
   if (!m_approximateOutput.isDefined()) {
     /* To ensure that the expression 'm_output' is a matrix or a complex, we
      * call 'evaluate'. */
diff --git a/apps/calculation/calculation_store.cpp b/apps/calculation/calculation_store.cpp
index 0eb708bff..37698613d 100644
--- a/apps/calculation/calculation_store.cpp
+++ b/apps/calculation/calculation_store.cpp
@@ -89,10 +89,10 @@ void CalculationStore::tidy() {
   }
 }
 
-Expression * CalculationStore::ansExpression(Context * context) {
+Expression CalculationStore::ansExpression(Context * context) {
   if (numberOfCalculations() == 0) {
     static Rational defaultExpression(0);
-    return &defaultExpression;
+    return defaultExpression;
   }
   Calculation * lastCalculation = calculationAtIndex(numberOfCalculations()-1);
   /* Special case: the exact output is a Store/Equal expression.
@@ -100,10 +100,10 @@ Expression * CalculationStore::ansExpression(Context * context) {
    * To avoid turning 'ans->A' in '2->A->A' (or 2->A=A) which cannot be parsed),
    * ans is replaced by the approximation output in when any Store or Equal
    * expression appears.*/
-  bool exactOuptutInvolvesStoreEqual = lastCalculation->exactOutput(context)->recursivelyMatches([](const Expression * e, Context & context) {
-          return e->type() == Expression::Type::Store || e->type() == Expression::Type::Equal;
+  bool exactOuptutInvolvesStoreEqual = lastCalculation->exactOutput(context).recursivelyMatches([](const Expression e, Context & context) {
+          return e.type() == ExpressionNode::Type::Store || e.type() == ExpressionNode::Type::Equal;
         }, *context);
-  if (lastCalculation->input()->isApproximate(*context) || exactOuptutInvolvesStoreEqual) {
+  if (lastCalculation->input().isApproximate(*context) || exactOuptutInvolvesStoreEqual) {
     return lastCalculation->approximateOutput(context);
   }
   return lastCalculation->exactOutput(context);
diff --git a/apps/calculation/calculation_store.h b/apps/calculation/calculation_store.h
index 158f1681a..58f6ebc5c 100644
--- a/apps/calculation/calculation_store.h
+++ b/apps/calculation/calculation_store.h
@@ -14,7 +14,7 @@ public:
   void deleteAll();
   int numberOfCalculations();
   void tidy();
-  Poincare::Expression * ansExpression(Poincare::Context * context);
+  Poincare::Expression ansExpression(Poincare::Context * context);
   static constexpr int k_maxNumberOfCalculations = 10;
 private:
   int m_startIndex;