diff --git a/apps/calculation/calculation.cpp b/apps/calculation/calculation.cpp
index 098b602d0..02da02862 100644
--- a/apps/calculation/calculation.cpp
+++ b/apps/calculation/calculation.cpp
@@ -13,29 +13,14 @@ Calculation::Calculation() :
   m_inputText(),
   m_exactOutputText(),
   m_approximateOutputText(),
-  m_input(nullptr),
-  m_exactOutput(nullptr),
-  m_approximateOutput(nullptr),
+  m_input(),
+  m_exactOutput(),
+  m_approximateOutput(),
   m_height(-1),
   m_equalSign(EqualSign::Unknown)
 {
 }
 
-Calculation::~Calculation() {
-  if (m_input != nullptr) {
-    delete m_input;
-    m_input = nullptr;
-  }
-  if (m_exactOutput != nullptr) {
-    delete m_exactOutput;
-    m_exactOutput = nullptr;
-  }
-  if (m_approximateOutput != nullptr) {
-    delete m_approximateOutput;
-    m_approximateOutput = nullptr;
-  }
-}
-
 Calculation& Calculation::operator=(const Calculation& other) {
   const char * otherInputText = other.m_inputText;
   const char * otherExactOutputText = other.m_exactOutputText;
@@ -115,18 +100,15 @@ const char * Calculation::approximateOutputText() {
   return m_approximateOutputText;
 }
 
-Expression * Calculation::input() {
-  if (m_input == nullptr) {
+Expression Calculation::input() {
+  if (!m_input.isDefined()) {
     m_input = Expression::parse(m_inputText);
   }
   return m_input;
 }
 
 LayoutRef Calculation::createInputLayout() {
-  if (input() != nullptr) {
-    return input()->createLayout(Preferences::PrintFloatMode::Decimal, PrintFloat::k_numberOfStoredSignificantDigits);
-  }
-  return LayoutRef(nullptr);
+  return input().createLayout(Preferences::PrintFloatMode::Decimal, PrintFloat::k_numberOfStoredSignificantDigits);
 }
 
 bool Calculation::isEmpty() {
@@ -144,7 +126,8 @@ bool Calculation::isEmpty() {
 }
 
 void Calculation::tidy() {
-  if (m_input != nullptr) {
+// TODO: we might want to do something here? To empty the pool?
+/*  if (m_input != nullptr) {
     delete m_input;
   }
   m_input = nullptr;
@@ -155,52 +138,41 @@ void Calculation::tidy() {
   if (m_approximateOutput != nullptr) {
     delete m_approximateOutput;
   }
-  m_approximateOutput = nullptr;
+  m_approximateOutput = nullptr;*/
   m_height = -1;
   m_equalSign = EqualSign::Unknown;
 }
 
 Expression * Calculation::exactOutput(Context * context) {
-  if (m_exactOutput == nullptr) {
+  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
      * 'sqrt(2)/2 = 0.999906' (which is totally wrong) instead of
      * 'cos(pi/4) = 0.999906' (which is true in degree). */
     m_exactOutput = Expression::parse(m_exactOutputText);
-    if (m_exactOutput == nullptr) {
-      m_exactOutput = new Undefined();
+    if (!m_exactOutput.isDefined()) {
+      m_exactOutput = Undefined();
     }
   }
   return m_exactOutput;
 }
 
 LayoutRef Calculation::createExactOutputLayout(Context * context) {
-  if (exactOutput(context) != nullptr) {
-    return PoincareHelpers::CreateLayout(exactOutput(context));
-  }
-  return LayoutRef(nullptr);
+  return PoincareHelpers::CreateLayout(exactOutput(context));
 }
 
 Expression * Calculation::approximateOutput(Context * context) {
-  if (m_approximateOutput == nullptr) {
+  if (!m_approximateOutput.isDefined()) {
     /* To ensure that the expression 'm_output' is a matrix or a complex, we
      * call 'evaluate'. */
-    Expression * exp = Expression::parse(m_approximateOutputText);
-    if (exp != nullptr) {
-      m_approximateOutput = PoincareHelpers::Approximate<double>(exp, *context);
-      delete exp;
-    } else {
-      m_approximateOutput = new Undefined();
-    }
+    Expression exp = Expression::parse(m_approximateOutputText);
+    m_approximateOutput = PoincareHelpers::Approximate<double>(exp, *context);
   }
   return m_approximateOutput;
 }
 
 LayoutRef Calculation::createApproximateOutputLayout(Context * context) {
-  if (approximateOutput(context) != nullptr) {
-    return PoincareHelpers::CreateLayout(approximateOutput(context));
-  }
-  return LayoutRef(nullptr);
+  return PoincareHelpers::CreateLayout(approximateOutput(context));
 }
 
 bool Calculation::shouldOnlyDisplayApproximateOutput(Context * context) {
@@ -210,14 +182,14 @@ bool Calculation::shouldOnlyDisplayApproximateOutput(Context * context) {
   if (strcmp(m_exactOutputText, "undef") == 0) {
     return true;
   }
-  return input()->isApproximate(*context);
+  return input().isApproximate(*context);
 }
 
 Calculation::EqualSign Calculation::exactAndApproximateDisplayedOutputsAreEqual(Poincare::Context * context) {
   if (m_equalSign != EqualSign::Unknown) {
     return m_equalSign;
   }
-  m_equalSign = exactOutput(context)->isEqualToItsApproximationLayout(approximateOutput(context), k_printedExpressionSize, Preferences::sharedPreferences()->angleUnit(), Preferences::sharedPreferences()->displayMode(), Preferences::sharedPreferences()->numberOfSignificantDigits(), *context) ? EqualSign::Equal : EqualSign::Approximation;
+  m_equalSign = exactOutput(context).isEqualToItsApproximationLayout(approximateOutput(context), k_printedExpressionSize, Preferences::sharedPreferences()->angleUnit(), Preferences::sharedPreferences()->displayMode(), Preferences::sharedPreferences()->numberOfSignificantDigits(), *context) ? EqualSign::Equal : EqualSign::Approximation;
   return m_equalSign;
 }
 
diff --git a/apps/calculation/calculation.h b/apps/calculation/calculation.h
index 7e3325780..0a5ba38c0 100644
--- a/apps/calculation/calculation.h
+++ b/apps/calculation/calculation.h
@@ -16,22 +16,21 @@ public:
     Equal
   };
   Calculation();
-  ~Calculation(); // Delete expression and layout, if needed
   Calculation& operator=(const Calculation& other);
   Calculation(const Calculation& other) = delete;
   Calculation(Calculation&& other) = delete;
   Calculation& operator=(Calculation&& other) = delete;
   /* c.reset() is the equivalent of c = Calculation() without copy assingment. */
   void reset();
-  void setContent(const char * c, Poincare::Context * context, Poincare::Expression * ansExpression);
+  void setContent(const char * c, Poincare::Context * context, Poincare::Expression ansExpression);
   KDCoordinate height(Poincare::Context * context);
   const char * inputText();
   const char * exactOutputText();
   const char * approximateOutputText();
-  Poincare::Expression * input();
+  Poincare::Expression input();
   Poincare::LayoutRef createInputLayout();
-  Poincare::Expression * approximateOutput(Poincare::Context * context);
-  Poincare::Expression * exactOutput(Poincare::Context * context);
+  Poincare::Expression approximateOutput(Poincare::Context * context);
+  Poincare::Expression exactOutput(Poincare::Context * context);
   Poincare::LayoutRef createExactOutputLayout(Poincare::Context * context);
   Poincare::LayoutRef createApproximateOutputLayout(Poincare::Context * context);
   bool isEmpty();
@@ -47,9 +46,9 @@ private:
   char m_inputText[k_printedExpressionSize];
   char m_exactOutputText[k_printedExpressionSize];
   char m_approximateOutputText[k_printedExpressionSize];
-  Poincare::Expression * m_input;
-  Poincare::Expression * m_exactOutput;
-  Poincare::Expression * m_approximateOutput;
+  Poincare::Expression m_input;
+  Poincare::Expression m_exactOutput;
+  Poincare::Expression m_approximateOutput;
   KDCoordinate m_height;
   EqualSign m_equalSign;
 };