diff --git a/poincare/include/poincare/absolute_value.h b/poincare/include/poincare/absolute_value.h
index b9f8238ce..62e419bc7 100644
--- a/poincare/include/poincare/absolute_value.h
+++ b/poincare/include/poincare/absolute_value.h
@@ -13,7 +13,7 @@ public:
   Type type() const override;
   Sign sign() const override { return Sign::Positive; }
 private:
-  Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) override;
+  Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const override;
   /* Layout */
   LayoutRef createLayout(Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override;
   int serialize(char * buffer, int bufferSize, Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override {
diff --git a/poincare/include/poincare/expression.h b/poincare/include/poincare/expression.h
index 1c2300d7e..201efae79 100644
--- a/poincare/include/poincare/expression.h
+++ b/poincare/include/poincare/expression.h
@@ -22,7 +22,7 @@ public:
   Expression() : Expression(nullptr) {}
   virtual ~Expression() = default;
   static Expression parse(char const * string);
-  Expression replaceSymbolWithExpression(char symbol, Expression expression) { return node()->replaceSymbolWithExpression(symbol, expression); }
+  Expression replaceSymbolWithExpression(char symbol, Expression expression) const { return node()->replaceSymbolWithExpression(symbol, expression); }
 
   /* Reference */
   ExpressionNode * node() const override {
@@ -43,7 +43,7 @@ public:
   /* Properties */
   ExpressionNode::Type type() const { return node()->type(); }
   ExpressionNode::Sign sign() const { return node()->sign(); }
-  Expression setSign(ExpressionNode::Sign s, Context & context, Preferences::AngleUnit angleUnit);
+  Expression setSign(ExpressionNode::Sign s, Context & context, Preferences::AngleUnit angleUnit) const;
   bool isUndefinedOrAllocationFailure() const { return node()->type() == ExpressionNode::Type::Undefined || node()->type() == ExpressionNode::Type::AllocationFailure; }
   bool isNumber() const { return node()->isNumber(); }
   bool isRationalZero() const;
diff --git a/poincare/include/poincare/expression_node.h b/poincare/include/poincare/expression_node.h
index 04fda7da7..0b2c16de0 100644
--- a/poincare/include/poincare/expression_node.h
+++ b/poincare/include/poincare/expression_node.h
@@ -100,8 +100,8 @@ public:
   };
   virtual Sign sign() const { return Sign::Unknown; }
   virtual bool isNumber() const { return false; }
-  /*!*/ virtual Expression replaceSymbolWithExpression(char symbol, Expression expression);
-  /*!*/ virtual Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit);
+  /*!*/ virtual Expression replaceSymbolWithExpression(char symbol, Expression expression) const;
+  /*!*/ virtual Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const;
   virtual int polynomialDegree(char symbolName) const;
   /*!*/ virtual int getPolynomialCoefficients(char symbolName, Expression coefficients[]) const;
   typedef bool (*isVariableTest)(char c);
diff --git a/poincare/include/poincare/integer.h b/poincare/include/poincare/integer.h
index 598d9b491..7657bdd81 100644
--- a/poincare/include/poincare/integer.h
+++ b/poincare/include/poincare/integer.h
@@ -139,7 +139,7 @@ public:
 
   // ExpressionNode
   Sign sign() const override { return m_negative ? Sign::Negative : Sign::Positive; }
-  Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) override;
+  Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const override;
 
   void setNegative(bool negative);
 
@@ -215,7 +215,7 @@ private:
 
   // Simplification
   Expression shallowReduce(Context & context, Preferences::AngleUnit angleUnit) const;
-  Expression setSign(ExpressionNode::Sign s, Context & context, Preferences::AngleUnit angleUnit);
+  Expression setSign(ExpressionNode::Sign s, Context & context, Preferences::AngleUnit angleUnit) const;
 };
 
 struct IntegerDivision {
diff --git a/poincare/include/poincare/multiplication.h b/poincare/include/poincare/multiplication.h
index 4764a5928..abb614cdc 100644
--- a/poincare/include/poincare/multiplication.h
+++ b/poincare/include/poincare/multiplication.h
@@ -32,7 +32,7 @@ public:
   template<typename T> static MatrixComplex<T> computeOnMatrices(const MatrixComplex<T> m, const MatrixComplex<T> n);
 private:
   /* Property */
-  Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) override;
+  Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const override;
   /* Layout */
   bool needsParenthesesWithParent(SerializableNode * parentNode) const override;
   LayoutRef createLayout(Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override;
diff --git a/poincare/include/poincare/power.h b/poincare/include/poincare/power.h
index 96f6e247a..b7371394d 100644
--- a/poincare/include/poincare/power.h
+++ b/poincare/include/poincare/power.h
@@ -24,7 +24,7 @@ public:
   // Properties
   virtual Type type() const override { return Type::Power; }
   virtual Sign sign() const override;
-  virtual Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) override;
+  virtual Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const override;
 
   int polynomialDegree(char symbolName) const override;
   int privateGetPolynomialCoefficients(char symbolName, Expression * coefficients[]) const override;
@@ -76,8 +76,8 @@ public:
   Power(Expression base, Expression exponent);
   Power(const PowerNode * n) : Expression(n) {}
 
-  Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit);
-  Expression shallowReduce(Context & context, Preferences::AngleUnit angleUnit);
+  Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const;
+  Expression shallowReduce(Context & context, Preferences::AngleUnit angleUnit) const;
 
 };
 
diff --git a/poincare/include/poincare/random.h b/poincare/include/poincare/random.h
index a80a1ed9b..77189ea0d 100644
--- a/poincare/include/poincare/random.h
+++ b/poincare/include/poincare/random.h
@@ -14,7 +14,7 @@ public:
   Sign sign() const override { return Sign::Positive; }
   template<typename T> static T random();
 private:
-  Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) override;
+  Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const override;
   /* Layout */
   LayoutRef createLayout(Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override {
     return LayoutHelper::Prefix(this, floatDisplayMode, numberOfSignificantDigits, name());
diff --git a/poincare/include/poincare/rational.h b/poincare/include/poincare/rational.h
index 58cb1c231..0c4799d5f 100644
--- a/poincare/include/poincare/rational.h
+++ b/poincare/include/poincare/rational.h
@@ -55,7 +55,7 @@ public:
 private:
   int simplificationOrderSameType(const ExpressionNode * e, bool canBeInterrupted) const override;
   Expression shallowBeautify(Context & context, Preferences::AngleUnit angleUnit) const override;
-  Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) override;
+  Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const override;
   Expression denominator(Context & context, Preferences::AngleUnit angleUnit) const override;
   bool m_negative;
   size_t m_numberOfDigitsNumerator;
diff --git a/poincare/include/poincare/symbol.h b/poincare/include/poincare/symbol.h
index 2480c7617..dca89239c 100644
--- a/poincare/include/poincare/symbol.h
+++ b/poincare/include/poincare/symbol.h
@@ -24,7 +24,7 @@ public:
   // Expression Properties
   Type type() const override { return Type::Symbol; }
   Sign sign() const override;
-  Expression replaceSymbolWithExpression(char symbol, Expression expression) override;
+  Expression replaceSymbolWithExpression(char symbol, Expression expression) const override;
   int polynomialDegree(char symbolName) const override;
   int getPolynomialCoefficients(char symbolName, Expression coefficients[]) const override;
   int getVariables(isVariableTest isVariable, char * variables) const override;
diff --git a/poincare/src/absolute_value.cpp b/poincare/src/absolute_value.cpp
index 38a9e7032..5df5ade5d 100644
--- a/poincare/src/absolute_value.cpp
+++ b/poincare/src/absolute_value.cpp
@@ -18,7 +18,7 @@ Expression * AbsoluteValue::clone() const {
   return a;
 }
 
-Expression * AbsoluteValue::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) {
+Expression * AbsoluteValue::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const {
   assert(s == Sign::Positive);
   return this;
 }
diff --git a/poincare/src/expression_node.cpp b/poincare/src/expression_node.cpp
index ad7b0cc9f..e9a74a720 100644
--- a/poincare/src/expression_node.cpp
+++ b/poincare/src/expression_node.cpp
@@ -10,7 +10,7 @@ ExpressionNode * ExpressionNode::FailedAllocationStaticNode() {
   return &FailureNode;
 }
 
-Expression ExpressionNode::replaceSymbolWithExpression(char symbol, Expression expression) {
+Expression ExpressionNode::replaceSymbolWithExpression(char symbol, Expression expression) const {
   Expression e = Expression(this);
   int nbChildren = e.numberOfChildren();
   for (int i = 0; i < nbChildren; i++) {
@@ -20,7 +20,7 @@ Expression ExpressionNode::replaceSymbolWithExpression(char symbol, Expression e
   return e;
 }
 
-Expression ExpressionNode::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) {
+Expression ExpressionNode::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const {
   assert(false);
   return Expression(nullptr);
 }
diff --git a/poincare/src/integer.cpp b/poincare/src/integer.cpp
index 2a10bdb8c..7197c0be0 100644
--- a/poincare/src/integer.cpp
+++ b/poincare/src/integer.cpp
@@ -433,7 +433,7 @@ size_t IntegerNode::size() const {
   return m_numberOfDigits*sizeof(native_uint_t)+sizeof(IntegerNode);
 }
 
-Expression IntegerNode::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) {
+Expression IntegerNode::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const {
   return Integer(this).setSign(s, context, angleUnit);
 }
 
@@ -596,7 +596,7 @@ Expression Integer::shallowReduce(Context & context, Preferences::AngleUnit angl
   return Rational(*this, Integer(1));
 }
 
-Expression Integer::setSign(ExpressionNode::Sign s, Context & context, Preferences::AngleUnit angleUnit) {
+Expression Integer::setSign(ExpressionNode::Sign s, Context & context, Preferences::AngleUnit angleUnit) const {
   Integer signedInteger = *this;
   signedInteger.setNegative(s == ExpressionNode::Sign::Negative);
   return signedInteger;
diff --git a/poincare/src/multiplication.cpp b/poincare/src/multiplication.cpp
index 2712099e1..46c3c45cc 100644
--- a/poincare/src/multiplication.cpp
+++ b/poincare/src/multiplication.cpp
@@ -103,7 +103,7 @@ Expression::Sign Multiplication::sign() const {
   return (Sign)sign;
 }
 
-Expression * Multiplication::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) {
+Expression * Multiplication::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const {
   assert(s == Sign::Positive);
   for (int i = 0; i < numberOfChildren(); i++) {
     if (operand(i)->sign() == Sign::Negative) {
diff --git a/poincare/src/power.cpp b/poincare/src/power.cpp
index aa23a29c2..44cbcbbac 100644
--- a/poincare/src/power.cpp
+++ b/poincare/src/power.cpp
@@ -101,11 +101,11 @@ int Power::getPolynomialCoefficients(char symbolName, Expression coefficients[])
   return -1;
 }
 
-Expression PowerNode::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) {
+Expression PowerNode::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const {
   return Power(this).setSign(s, context, angleUnit);
 }
 
-Expression Power::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) {
+Expression Power::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const {
   assert(s == Sign::Positive);
   assert(childAtIndex(0).sign() == Sign::Negative);
   return Power(childAtIndex(0).setSign(Sign::Positive, context, angleUnit), childAtIndex(1));
diff --git a/poincare/src/random.cpp b/poincare/src/random.cpp
index 09969225c..649571737 100644
--- a/poincare/src/random.cpp
+++ b/poincare/src/random.cpp
@@ -17,7 +17,7 @@ Expression * Random::clone() const {
   return a;
 }
 
-Expression * Random::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) {
+Expression * Random::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const {
   assert(s == Sign::Positive);
   return this;
 }
diff --git a/poincare/src/rational.cpp b/poincare/src/rational.cpp
index 96aa2ce2d..fb93cbca0 100644
--- a/poincare/src/rational.cpp
+++ b/poincare/src/rational.cpp
@@ -77,7 +77,7 @@ int RationalNode::serialize(char * buffer, int bufferSize, Preferences::PrintFlo
 
 // Expression subclassing
 
-Expression RationalNode::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) {
+Expression RationalNode::setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit) const {
   return Rational(this).setSign(s);
 }
 
diff --git a/poincare/src/symbol.cpp b/poincare/src/symbol.cpp
index df46e2ecf..7fb91cbcb 100644
--- a/poincare/src/symbol.cpp
+++ b/poincare/src/symbol.cpp
@@ -32,7 +32,7 @@ ExpressionNode::Sign SymbolNode::sign() const {
   return Sign::Unknown;
 }
 
-Expression SymbolNode::replaceSymbolWithExpression(char symbol, Expression expression) {
+Expression SymbolNode::replaceSymbolWithExpression(char symbol, Expression expression) const {
   if (m_name == symbol) {
     Expression value = expression.clone();
     if (parent() && value.needsParenthesesWithParent(parent())) {