diff --git a/poincare/Makefile b/poincare/Makefile
index 66176533f..42a7206a2 100644
--- a/poincare/Makefile
+++ b/poincare/Makefile
@@ -34,6 +34,7 @@ objs += $(addprefix poincare/src/,\
   approximation_helper.o\
   layout_helper.o\
   simplification_helper.o\
+  global_context.o\
 )
 
 objsExpected += $(addprefix poincare/src/,\
diff --git a/poincare/include/poincare/decimal.h b/poincare/include/poincare/decimal.h
index e6992fac5..4f7c7a2ca 100644
--- a/poincare/include/poincare/decimal.h
+++ b/poincare/include/poincare/decimal.h
@@ -83,11 +83,11 @@ public:
   static int Exponent(const char * integralPart, int integralPartLength, const char * fractionalPart, int fractionalPartLength, const char * exponent, int exponentLength, bool exponentNegative);
   Decimal(const char * integralPart, int integralPartLength, const char * fractionalPart, int fractionalPartLength, bool negative, int exponent);
   Decimal(const DecimalNode * node) : Number(node) {}
+  Decimal(Integer m, int e);
   constexpr static int k_maxExponentLength = 4;
 private:
   DecimalNode * node() const override { return static_cast<DecimalNode *>(Number::node()); }
   template <typename T> Decimal(T f);
-  Decimal(Integer m, int e);
   Decimal(size_t size) : Number(nullptr) {
     TreeNode * node = TreePool::sharedPool()->createTreeNode<DecimalNode>(size);
     m_identifier = node->identifier();
diff --git a/poincare/include/poincare/global_context.h b/poincare/include/poincare/global_context.h
index 36a753907..1a1203e04 100644
--- a/poincare/include/poincare/global_context.h
+++ b/poincare/include/poincare/global_context.h
@@ -2,9 +2,10 @@
 #define POINCARE_GLOBAL_CONTEXT_H
 
 #include <poincare/context.h>
-#include <poincare/matrix.h>
-#include <poincare/approximation.h>
+//#include <poincare/matrix.h>
+#include <poincare/float.h>
 #include <poincare/decimal.h>
+#include <poincare/symbol.h>
 
 namespace Poincare {
 
@@ -17,22 +18,21 @@ public:
   GlobalContext();
   /* The expression recorded in global context is already a expression.
    * Otherwise, we would need the context and the angle unit to evaluate it */
-  const Expression expressionForSymbol(const SymbolReference symbol) override;
-  LayoutRef layoutForSymbol(const SymbolReference symbol, int numberOfSignificantDigits);
-  void setExpressionForSymbolName(const Expression expression, const SymbolReference symbol, Context & context) override;
+  const Expression expressionForSymbol(const Symbol symbol) override;
+  //LayoutRef layoutForSymbol(const Symbol symbol, int numberOfSignificantDigits);
+  void setExpressionForSymbolName(const Expression expression, const Symbol symbol, Context & context) override;
   static constexpr uint16_t k_maxNumberOfScalarExpressions = 26;
   static constexpr uint16_t k_maxNumberOfListExpressions = 10;
   static constexpr uint16_t k_maxNumberOfMatrixExpressions = 10;
 private:
-  static Decimal * defaultExpression();
-  int symbolIndex(const Symbol * symbol) const;
+  static Decimal defaultExpression();
+  int symbolIndex(const Symbol symbol) const;
   Expression m_expressions[k_maxNumberOfScalarExpressions];
-  MatrixReference m_matrixExpressions[k_maxNumberOfMatrixExpressions];
+  //Matrix m_matrixExpressions[k_maxNumberOfMatrixExpressions];
   /* Matrix layout memoization */
-  LayoutRef m_matrixLayouts[k_maxNumberOfMatrixExpressions];
-  Approximation<double> m_pi;
-  Approximation<double> m_e;
-  Approximation<double> m_i;
+  //LayoutRef m_matrixLayouts[k_maxNumberOfMatrixExpressions];
+  Float<double> m_pi;
+  Float<double> m_e;
 };
 
 }
diff --git a/poincare/include/poincare/symbol.h b/poincare/include/poincare/symbol.h
index 8ea26a60d..8f2d9ff18 100644
--- a/poincare/include/poincare/symbol.h
+++ b/poincare/include/poincare/symbol.h
@@ -107,9 +107,11 @@ public:
   Expression shallowReduce(Context& context, Preferences::AngleUnit angleUnit) const;
   Expression replaceSymbolWithExpression(char symbol, Expression expression) const;
   int getPolynomialCoefficients(char symbolName, Expression coefficients[]) const;
+
+  // Symbol
+  char name() const { return node()->name(); }
 private:
   SymbolNode * node() const override { return static_cast<SymbolNode *>(Expression::node()); }
-  char name() const { return node()->name(); }
 };
 
 }
diff --git a/poincare/src/global_context.cpp b/poincare/src/global_context.cpp
index 116aa7243..c14a3e167 100644
--- a/poincare/src/global_context.cpp
+++ b/poincare/src/global_context.cpp
@@ -1,5 +1,4 @@
 #include <poincare/global_context.h>
-#include <poincare/matrix.h>
 #include <poincare/undefined.h>
 #include <poincare/preferences.h>
 #include <assert.h>
@@ -9,7 +8,7 @@
 namespace Poincare {
 
 GlobalContext::GlobalContext() :
-  m_matrixLayouts{
+/*  m_matrixLayouts{
     LayoutRef(nullptr),
     LayoutRef(nullptr),
     LayoutRef(nullptr),
@@ -19,74 +18,50 @@ GlobalContext::GlobalContext() :
     LayoutRef(nullptr),
     LayoutRef(nullptr),
     LayoutRef(nullptr),
-    LayoutRef(nullptr)}, //TODO find better way to initialize
+    LayoutRef(nullptr)},*/ //TODO find better way to initialize
   m_pi(M_PI),
-  m_e(M_E),
-  m_i(0.0, 1.0)
+  m_e(M_E)
 {
-  for (int i = 0; i < k_maxNumberOfScalarExpressions; i++) {
-    m_expressions[i] = nullptr;
-  }
-  for (int i = 0; i < k_maxNumberOfMatrixExpressions ; i++) {
-    m_matrixExpressions[i] = nullptr;
-  }
 }
 
-GlobalContext::~GlobalContext() {
-  for (int i = 0; i < k_maxNumberOfScalarExpressions; i++) {
-    if (m_expressions[i] != nullptr) {
-      delete m_expressions[i];
-    }
-    m_expressions[i] = nullptr;
-  }
-  for (int i = 0; i < k_maxNumberOfMatrixExpressions; i++) {
-    if (m_matrixExpressions[i] != nullptr) {
-      delete m_matrixExpressions[i];
-    }
-    m_matrixExpressions[i] = nullptr;
-  }
-}
-
-Decimal * GlobalContext::defaultExpression() {
+Decimal GlobalContext::defaultExpression() {
   static Decimal defaultExpression(Integer(0), 0);
-  return &defaultExpression;
+  return defaultExpression;
 }
 
-int GlobalContext::symbolIndex(const Symbol * symbol) const {
-  if (SymbolReference::isMatrixSymbol(symbol->name())) {
-    return symbol->name() - (char)Symbol::SpecialSymbols::M0;
+int GlobalContext::symbolIndex(const Symbol symbol) const {
+  if (Symbol::isMatrixSymbol(symbol.name())) {
+    return symbol.name() - (char)Symbol::SpecialSymbols::M0;
   }
-  if (SymbolReference::isScalarSymbol(symbol->name())) {
-    return symbol->name() - 'A';
+  if (Symbol::isScalarSymbol(symbol.name())) {
+    return symbol.name() - 'A';
   }
   return -1;
 }
 
-const Expression * GlobalContext::expressionForSymbol(const Symbol * symbol) {
-  if (symbol->name() == Ion::Charset::IComplex) {
-    return &m_i;
+const Expression GlobalContext::expressionForSymbol(const Symbol symbol) {
+  if (symbol.name() == Ion::Charset::SmallPi) {
+    return m_pi;
   }
-  if (symbol->name() == Ion::Charset::SmallPi) {
-    return &m_pi;
-  }
-  if (symbol->name() == Ion::Charset::Exponential) {
-    return &m_e;
+  if (symbol.name() == Ion::Charset::Exponential) {
+    return m_e;
   }
   int index = symbolIndex(symbol);
-  if (SymbolReference::isMatrixSymbol(symbol->name()) {
-    return m_matrixExpressions[index];
+  if (Symbol::isMatrixSymbol(symbol.name())) {
+    return Expression();
+    //return m_matrixExpressions[index]; // TODO: implement when matrix is done
   }
   if (index < 0 || index >= k_maxNumberOfScalarExpressions) {
-    return nullptr;
+    return Expression();
   }
-  if (m_expressions[index] == nullptr) {
-    return defaultExpression();
+  if (m_expressions[index].isDefined()) {
+    return m_expressions[index];
   }
-  return m_expressions[index];
+  return defaultExpression();
 }
 
-LayoutRef GlobalContext::layoutForSymbol(const Symbol * symbol, int numberOfSignificantDigits) {
-  if (SymbolReference::isMatrixSymbol(symbol->name()) {
+/*LayoutRef GlobalContext::layoutForSymbol(const Symbol * symbol, int numberOfSignificantDigits) {
+  if (Symbol::isMatrixSymbol(symbol.name()) {
     int index = symbolIndex(symbol);
     if (!m_matrixLayouts[index].isDefined() && m_matrixExpressions[index] != nullptr) {
       m_matrixLayouts[index] = m_matrixExpressions[index]->createLayout(Preferences::PrintFloatMode::Decimal, numberOfSignificantDigits);
@@ -94,26 +69,19 @@ LayoutRef GlobalContext::layoutForSymbol(const Symbol * symbol, int numberOfSign
     return m_matrixLayouts[index];
   }
   return nullptr;
-}
+}*/
 
-void GlobalContext::setExpressionForSymbolName(const Expression * expression, const Symbol * symbol, Context & context) {
+void GlobalContext::setExpressionForSymbolName(const Expression expression, const Symbol symbol, Context & context) {
   int index = symbolIndex(symbol);
- if (SymbolReference::isMatrixSymbol(symbol->name()) {
-    int indexMatrix = symbol->name() - (char)Symbol::SpecialSymbols::M0;
+ if (Symbol::isMatrixSymbol(symbol.name())) {
+    int indexMatrix = symbol.name() - (char)Symbol::SpecialSymbols::M0;
     assert(indexMatrix >= 0 && indexMatrix < k_maxNumberOfMatrixExpressions);
-    Expression * evaluation = expression ? expression->approximate<double>(context, Preferences::sharedPreferences()->angleUnit(), Preferences::sharedPreferences()->complexFormat()) : nullptr; // evaluate before deleting anything (to be able to evaluate M1+2->M1)
-    if (m_matrixExpressions[indexMatrix] != nullptr) {
-      delete m_matrixExpressions[indexMatrix];
-      m_matrixExpressions[indexMatrix] = nullptr;
-    }
-    if (m_matrixLayouts[indexMatrix] != nullptr) {
-      m_matrixLayouts[indexMatrix] = LayoutRef(nullptr);
-    }
-    if (evaluation != nullptr) {
-      if (evaluation->type() != Expression::Type::Matrix) {
-        m_matrixExpressions[indexMatrix] = new Matrix(&evaluation, 1, 1, false);
+    Expression evaluation = expression.isDefined() ? expression.approximate<double>(context, Preferences::sharedPreferences()->angleUnit(), Preferences::sharedPreferences()->complexFormat()) : Expression(); // evaluate before deleting anything (to be able to evaluate M1+2->M1)
+    if (evaluation.isDefined()) {
+      if (evaluation.type() != ExpressionNode::Type::Matrix) {
+        //m_matrixExpressions[indexMatrix] = new Matrix(&evaluation, 1, 1, false);
       } else {
-        m_matrixExpressions[indexMatrix] = static_cast<Matrix *>(evaluation);
+        //m_matrixExpressions[indexMatrix] = static_cast<Matrix *>(evaluation);
       }
     }
     return;
@@ -121,17 +89,12 @@ void GlobalContext::setExpressionForSymbolName(const Expression * expression, co
   if (index < 0 || index >= k_maxNumberOfScalarExpressions) {
     return;
   }
-  Expression * evaluation = expression ? expression->approximate<double>(context, Preferences::sharedPreferences()->angleUnit(), Preferences::sharedPreferences()->complexFormat()) : nullptr; // evaluate before deleting anything (to be able to evaluate A+2->A)
-  if (m_expressions[index] != nullptr) {
-    delete m_expressions[index];
-    m_expressions[index] = nullptr;
-  }
-  if (evaluation == nullptr) {
+  Expression evaluation = expression.isDefined() ? expression.approximate<double>(context, Preferences::sharedPreferences()->angleUnit(), Preferences::sharedPreferences()->complexFormat()) : Expression(); // evaluate before deleting anything (to be able to evaluate A+2->A)
+  if (!evaluation.isDefined()) {
     return;
   }
-  if (evaluation->type() == Expression::Type::Matrix) {
-    m_expressions[index] = new Undefined();
-    delete evaluation;
+  if (evaluation.type() == ExpressionNode::Type::Matrix) {
+    m_expressions[index] = Undefined();
   } else {
     m_expressions[index] = evaluation;
   }