diff --git a/app/app.cpp b/app/app.cpp
index eede4f5e7..d1c9814da 100644
--- a/app/app.cpp
+++ b/app/app.cpp
@@ -66,7 +66,7 @@ static void interactive_expression_parsing() {
     clear_screen();
     Expression * e = Expression::parse(text_input);
     if (e) {
-      ExpressionLayout * l = e->createLayout(nullptr);
+      ExpressionLayout * l = e->createLayout();
       if (l) {
         l->draw(KDPointMake(0,10));
         delete l;
diff --git a/poincare/Makefile b/poincare/Makefile
index 190844c66..d2b7c62c6 100644
--- a/poincare/Makefile
+++ b/poincare/Makefile
@@ -24,7 +24,6 @@ objs += $(addprefix poincare/src/layout/,\
   exponent_layout.o\
   expression_layout.o\
   fraction_layout.o\
-  function_layout.o\
   horizontal_layout.o\
   string_layout.o\
 )
diff --git a/poincare/include/poincare/addition.h b/poincare/include/poincare/addition.h
index 80f64a726..591c020b3 100644
--- a/poincare/include/poincare/addition.h
+++ b/poincare/include/poincare/addition.h
@@ -6,10 +6,11 @@
 class Addition : public CommutativeOperation {
   using CommutativeOperation::CommutativeOperation;
   public:
-    ExpressionLayout * createLayout(ExpressionLayout * parent) override;
     Type type() override;
     float operateApproximatevelyOn(float a, float b) override;
     Expression * clone() override;
+  protected:
+    char operatorChar() override;
 };
 
 #endif
diff --git a/poincare/include/poincare/commutative_operation.h b/poincare/include/poincare/commutative_operation.h
index a9baf31f9..e7e01f8d1 100644
--- a/poincare/include/poincare/commutative_operation.h
+++ b/poincare/include/poincare/commutative_operation.h
@@ -10,8 +10,10 @@ class CommutativeOperation : public Expression {
     Expression * operand(int i) override;
     int numberOfOperands() override;
     float approximate(Context& context) override;
+    ExpressionLayout * createLayout() override;
   protected:
     virtual float operateApproximatevelyOn(float a, float b) = 0;
+    virtual char operatorChar() = 0;
     int m_numberOfOperands;
     Expression ** m_operands;
 };
diff --git a/poincare/include/poincare/expression.h b/poincare/include/poincare/expression.h
index cedb2ec46..499944a6b 100644
--- a/poincare/include/poincare/expression.h
+++ b/poincare/include/poincare/expression.h
@@ -24,7 +24,7 @@ class Expression {
     static Expression * parse(char const * string);
     virtual ~Expression();
 
-    virtual ExpressionLayout * createLayout(ExpressionLayout * parent) = 0; // Returned object must be deleted
+    virtual ExpressionLayout * createLayout() = 0; // Returned object must be deleted
     virtual Expression * operand(int i) = 0;
     virtual int numberOfOperands() = 0;
     virtual Expression * clone() = 0;
diff --git a/poincare/include/poincare/expression_layout.h b/poincare/include/poincare/expression_layout.h
index 52f822fc4..a46c005d2 100644
--- a/poincare/include/poincare/expression_layout.h
+++ b/poincare/include/poincare/expression_layout.h
@@ -7,12 +7,13 @@ extern "C" {
 
 class ExpressionLayout {
   public:
-    ExpressionLayout(ExpressionLayout * parent);
+    ExpressionLayout();
     virtual ~ExpressionLayout();
 
     void draw(KDPoint point);
     KDPoint origin();
     KDSize size();
+    void setParent(ExpressionLayout* parent);
   protected:
     virtual void render(KDPoint point) = 0;
     virtual KDSize computeSize() = 0;
@@ -21,7 +22,7 @@ class ExpressionLayout {
   private:
     KDPoint absoluteOrigin();
     //void computeLayout();//ExpressionLayout * parent, uint16_t childIndex);
-    ExpressionLayout * m_parent;
+    ExpressionLayout* m_parent;
     bool m_sized, m_positioned;
     KDRect m_frame;
 };
diff --git a/poincare/include/poincare/float.h b/poincare/include/poincare/float.h
index f95edf757..245a1e8d9 100644
--- a/poincare/include/poincare/float.h
+++ b/poincare/include/poincare/float.h
@@ -8,7 +8,7 @@ class Float : public LeafExpression {
     Float(float f);
     ~Float();
 
-    ExpressionLayout * createLayout(ExpressionLayout * parent) override;
+    ExpressionLayout * createLayout() override;
     float approximate(Context& context) override;
     Type type() override;
     Expression * clone() override;
diff --git a/poincare/include/poincare/fraction.h b/poincare/include/poincare/fraction.h
index 20c602908..23fbe9352 100644
--- a/poincare/include/poincare/fraction.h
+++ b/poincare/include/poincare/fraction.h
@@ -6,7 +6,7 @@
 class Fraction : public BinaryOperation {
   using BinaryOperation::BinaryOperation;
   public:
-    ExpressionLayout * createLayout(ExpressionLayout * parent) override;
+    ExpressionLayout * createLayout() override;
     float approximate(Context& context) override;
     Type type() override;
     Expression * clone() override;
diff --git a/poincare/include/poincare/function.h b/poincare/include/poincare/function.h
index e02e7e388..576832d25 100644
--- a/poincare/include/poincare/function.h
+++ b/poincare/include/poincare/function.h
@@ -7,7 +7,7 @@ class Function : public Expression {
   public:
     Function(Expression * arg, char* function_name, bool clone_operands=true);
     ~Function();
-    ExpressionLayout * createLayout(ExpressionLayout * parent) override;
+    ExpressionLayout * createLayout() override;
     Expression * operand(int i) override;
     int numberOfOperands() override;
   protected:
diff --git a/poincare/include/poincare/integer.h b/poincare/include/poincare/integer.h
index 9db01a62f..b29b2f7b0 100644
--- a/poincare/include/poincare/integer.h
+++ b/poincare/include/poincare/integer.h
@@ -34,7 +34,7 @@ class Integer : public LeafExpression {
     virtual bool identicalTo(Expression * e);
     */
     Expression * clone() override;
-    virtual ExpressionLayout * createLayout(ExpressionLayout * parent) override;
+    virtual ExpressionLayout * createLayout() override;
     float approximate(Context& context) override;
   private:
     int8_t ucmp(const Integer &other) const; // -1, 0, or 1
diff --git a/poincare/include/poincare/power.h b/poincare/include/poincare/power.h
index 0c91f2ccd..4f567a1df 100644
--- a/poincare/include/poincare/power.h
+++ b/poincare/include/poincare/power.h
@@ -6,7 +6,7 @@
 class Power : public BinaryOperation {
   using BinaryOperation::BinaryOperation;
   public:
-    ExpressionLayout * createLayout(ExpressionLayout * parent) override;
+    ExpressionLayout * createLayout() override;
     float approximate(Context& context) override;
     Type type() override;
     Expression * clone() override;
diff --git a/poincare/include/poincare/product.h b/poincare/include/poincare/product.h
index 048d6d606..4b4b50be1 100644
--- a/poincare/include/poincare/product.h
+++ b/poincare/include/poincare/product.h
@@ -6,10 +6,11 @@
 class Product : public CommutativeOperation {
   using CommutativeOperation::CommutativeOperation;
   public:
-    ExpressionLayout * createLayout(ExpressionLayout * parent) override;
     Type type() override;
     float operateApproximatevelyOn(float a, float b) override;
     Expression * clone() override;
+  protected:
+    char operatorChar() override;
 };
 
 #endif
diff --git a/poincare/include/poincare/subtraction.h b/poincare/include/poincare/subtraction.h
index 7dac515d3..5054bf390 100644
--- a/poincare/include/poincare/subtraction.h
+++ b/poincare/include/poincare/subtraction.h
@@ -6,7 +6,7 @@
 class Subtraction : public BinaryOperation {
   using BinaryOperation::BinaryOperation;
   public:
-    ExpressionLayout * createLayout(ExpressionLayout * parent) override;
+    ExpressionLayout * createLayout() override;
     float approximate(Context& context) override;
     Type type() override;
     Expression * clone() override;
diff --git a/poincare/include/poincare/symbol.h b/poincare/include/poincare/symbol.h
index 78967aa3b..b0e1ebaba 100644
--- a/poincare/include/poincare/symbol.h
+++ b/poincare/include/poincare/symbol.h
@@ -7,7 +7,7 @@ class Symbol : public LeafExpression {
   public:
     Symbol(char * name);
     ~Symbol();
-    ExpressionLayout * createLayout(ExpressionLayout * parent) override;
+    ExpressionLayout * createLayout() override;
     float approximate(Context& context) override;
     Type type() override;
     Expression * clone() override;
diff --git a/poincare/src/addition.cpp b/poincare/src/addition.cpp
index 15795ee7b..0783002dc 100644
--- a/poincare/src/addition.cpp
+++ b/poincare/src/addition.cpp
@@ -13,6 +13,6 @@ float Addition::operateApproximatevelyOn(float a, float b) {
   return a + b;
 }
 
-ExpressionLayout * Addition::createLayout(ExpressionLayout * parent) {
-  return new HorizontalLayout(parent, m_operands, m_numberOfOperands, '+');
+char Addition::operatorChar() {
+  return '+';
 }
diff --git a/poincare/src/commutative_operation.cpp b/poincare/src/commutative_operation.cpp
index 37252e0a0..f96c76f90 100644
--- a/poincare/src/commutative_operation.cpp
+++ b/poincare/src/commutative_operation.cpp
@@ -4,6 +4,9 @@ extern "C" {
 #include <stdlib.h>
 }
 
+#include "layout/horizontal_layout.h"
+#include "layout/string_layout.h"
+
 CommutativeOperation::CommutativeOperation(Expression ** operands, int numberOfOperands, bool cloneOperands) {
   assert(numberOfOperands >= 2);
   m_numberOfOperands = numberOfOperands;
@@ -42,3 +45,15 @@ float CommutativeOperation::approximate(Context& context) {
   }
   return result;
 }
+
+ExpressionLayout * CommutativeOperation::createLayout() {
+  int number_of_children = 2*m_numberOfOperands-1;
+  ExpressionLayout** children_layouts = (ExpressionLayout **)malloc(number_of_children*sizeof(ExpressionLayout *));
+  char string[2] = {operatorChar(), '\0'};
+  children_layouts[0] = m_operands[0]->createLayout();
+  for (int i=1; i<m_numberOfOperands; i++) {
+    children_layouts[2*i-1] = new StringLayout(string, 1);
+    children_layouts[2*i] = m_operands[i]->createLayout();
+  }
+  return new HorizontalLayout(children_layouts, number_of_children);
+}
diff --git a/poincare/src/float.cpp b/poincare/src/float.cpp
index 2a905b248..88fade139 100644
--- a/poincare/src/float.cpp
+++ b/poincare/src/float.cpp
@@ -21,7 +21,7 @@ Expression::Type Float::type() {
   return Expression::Type::Float;
 }
 
-ExpressionLayout * Float::createLayout(ExpressionLayout * parent) {
+ExpressionLayout * Float::createLayout() {
   assert(0); // Should not come here, ever...
   return nullptr;
 }
diff --git a/poincare/src/fraction.cpp b/poincare/src/fraction.cpp
index a5172bc3a..10893c814 100644
--- a/poincare/src/fraction.cpp
+++ b/poincare/src/fraction.cpp
@@ -6,8 +6,8 @@ Expression * Fraction::clone() {
   return new Fraction(m_operands, true);
 }
 
-ExpressionLayout * Fraction::createLayout(ExpressionLayout * parent) {
-  return new FractionLayout(parent, m_operands[0], m_operands[1]);
+ExpressionLayout * Fraction::createLayout() {
+  return new FractionLayout(m_operands[0]->createLayout(), m_operands[1]->createLayout());
 }
 
 float Fraction::approximate(Context& context) {
diff --git a/poincare/src/function.cpp b/poincare/src/function.cpp
index e0ac86286..9def96a61 100644
--- a/poincare/src/function.cpp
+++ b/poincare/src/function.cpp
@@ -2,7 +2,8 @@ extern "C" {
 #include <stdlib.h>
 }
 #include <poincare/function.h>
-#include "layout/function_layout.h"
+#include "layout/horizontal_layout.h"
+#include "layout/string_layout.h"
 
 Function::Function(Expression * arg, char* function_name, bool clone_operands) {
   m_arg = (Expression *)malloc(sizeof(Expression));
@@ -18,8 +19,15 @@ Function::~Function() {
   delete m_arg;
 }
 
-ExpressionLayout * Function::createLayout(ExpressionLayout * parent) {
-  return new FunctionLayout(parent, m_function_name, m_arg);
+ExpressionLayout * Function::createLayout() {
+  ExpressionLayout** children_layouts = (ExpressionLayout **)malloc(4*sizeof(ExpressionLayout *));
+  children_layouts[0] = new StringLayout(m_function_name, strlen(m_function_name));
+  char string[2] = {'-', '\0'};
+  children_layouts[1] = new StringLayout(string, 1);
+  children_layouts[2] = m_arg->createLayout();
+  string[0] = ')';
+  children_layouts[3] = new StringLayout(string, 1);
+  return new HorizontalLayout(children_layouts, 4);
 }
 
 Expression * Function::operand(int i) {
diff --git a/poincare/src/integer.cpp b/poincare/src/integer.cpp
index f073fc748..78de87385 100644
--- a/poincare/src/integer.cpp
+++ b/poincare/src/integer.cpp
@@ -268,7 +268,7 @@ Expression * Integer::clone() {
   clone->m_negative = m_negative;
   free(clone->m_digits);
   clone->m_digits = (native_uint_t *)malloc(m_numberOfDigits*sizeof(native_uint_t));
-  for (int i=0;i<m_numberOfDigits; i++) {
+  for (unsigned int i=0;i<m_numberOfDigits; i++) {
     clone->m_digits[i] = m_digits[i];
   }
   return clone;
@@ -320,7 +320,7 @@ Expression::Type Integer::type() {
   return Expression::Type::Integer;
 }
 
-ExpressionLayout * Integer::createLayout(ExpressionLayout * parent) {
+ExpressionLayout * Integer::createLayout() {
   char buffer[255];
 
   Integer base = Integer(10);
@@ -341,7 +341,7 @@ ExpressionLayout * Integer::createLayout(ExpressionLayout * parent) {
     buffer[j] = c;
   }
 
-  return new StringLayout(parent, buffer, size);
+  return new StringLayout(buffer, size);
 }
 
 bool Integer::valueEquals(Expression * e) {
diff --git a/poincare/src/layout/exponent_layout.cpp b/poincare/src/layout/exponent_layout.cpp
index 2dc202bf9..6f8b703fe 100644
--- a/poincare/src/layout/exponent_layout.cpp
+++ b/poincare/src/layout/exponent_layout.cpp
@@ -5,10 +5,10 @@
 // TODO(fraimundo): Find a better name.
 #define EXPONENT_HEIGHT 5
 
-ExponentLayout::ExponentLayout(ExpressionLayout * parent, Expression * base, Expression * exponent) :
-ExpressionLayout(parent) {
-  m_base_layout = base->createLayout(this);
-  m_exponent_layout = exponent->createLayout(this);
+ExponentLayout::ExponentLayout(ExpressionLayout * base_layout, ExpressionLayout * exponent_layout) :
+ExpressionLayout(), m_base_layout(base_layout), m_exponent_layout(exponent_layout) {
+  m_base_layout->setParent(this);
+  m_exponent_layout->setParent(this);
 }
 
 ExponentLayout::~ExponentLayout() {
diff --git a/poincare/src/layout/exponent_layout.h b/poincare/src/layout/exponent_layout.h
index 7f79fc64b..c29eacc1d 100644
--- a/poincare/src/layout/exponent_layout.h
+++ b/poincare/src/layout/exponent_layout.h
@@ -6,7 +6,7 @@
 
 class ExponentLayout : public ExpressionLayout {
   public:
-    ExponentLayout(ExpressionLayout * parent, Expression * base, Expression * exponent);
+    ExponentLayout(ExpressionLayout * base_layout, ExpressionLayout * exponent_layout);
     ~ExponentLayout();
   protected:
     void render(KDPoint point) override;
diff --git a/poincare/src/layout/expression_layout.cpp b/poincare/src/layout/expression_layout.cpp
index 54c15ac52..8a31b9c3e 100644
--- a/poincare/src/layout/expression_layout.cpp
+++ b/poincare/src/layout/expression_layout.cpp
@@ -2,8 +2,8 @@
 #include <stdlib.h>
 #include "string_layout.h"
 
-ExpressionLayout::ExpressionLayout(ExpressionLayout * parent) :
-  m_parent(parent),
+ExpressionLayout::ExpressionLayout() :
+  m_parent(nullptr),
   m_sized(false),
   m_positioned(false),
   m_frame(KDRectZero) {
@@ -52,3 +52,7 @@ KDSize ExpressionLayout::size() {
   }
   return m_frame.size;
 }
+
+void ExpressionLayout::setParent(ExpressionLayout* parent) {
+  m_parent = parent;
+}
diff --git a/poincare/src/layout/fraction_layout.cpp b/poincare/src/layout/fraction_layout.cpp
index d0d56f71d..c4ef1b3fb 100644
--- a/poincare/src/layout/fraction_layout.cpp
+++ b/poincare/src/layout/fraction_layout.cpp
@@ -10,19 +10,19 @@ static inline KDCoordinate max(KDCoordinate a, KDCoordinate b) {
 #define FRACTION_LINE_MARGIN 2
 #define FRACTION_LINE_HEIGHT 1
 
-FractionLayout::FractionLayout(ExpressionLayout * parent, Expression * numerator, Expression * denominator) :
-ExpressionLayout(parent) {
-  m_numerator = numerator->createLayout(this);
-  m_denominator = denominator->createLayout(this);
+FractionLayout::FractionLayout(ExpressionLayout * numerator_layout, ExpressionLayout * denominator_layout) :
+ExpressionLayout(), m_numerator_layout(numerator_layout), m_denominator_layout(denominator_layout) {
+  m_numerator_layout->setParent(this);
+  m_denominator_layout->setParent(this);
 }
 
 FractionLayout::~FractionLayout() {
-  delete m_denominator;
-  delete m_numerator;
+  delete m_denominator_layout;
+  delete m_numerator_layout;
 }
 
 void FractionLayout::render(KDPoint point) {
-  KDCoordinate fractionLineY = point.y + m_numerator->size().height + FRACTION_LINE_MARGIN;
+  KDCoordinate fractionLineY = point.y + m_numerator_layout->size().height + FRACTION_LINE_MARGIN;
 
   KDDrawLine(
       KDPointMake(point.x, fractionLineY),
@@ -32,17 +32,18 @@ void FractionLayout::render(KDPoint point) {
 
 KDSize FractionLayout::computeSize() {
   KDSize s;
-  s.width = max(m_numerator->size().width, m_denominator->size().width) + 2*FRACTION_BORDER_LENGTH;
-  s.height = m_numerator->size().height + FRACTION_LINE_MARGIN + FRACTION_LINE_HEIGHT + FRACTION_LINE_MARGIN + m_denominator->size().height;
+  s.width = max(m_numerator_layout->size().width, m_denominator_layout->size().width) + 2*FRACTION_BORDER_LENGTH;
+  s.height = m_numerator_layout->size().height + FRACTION_LINE_MARGIN
+    + FRACTION_LINE_HEIGHT + FRACTION_LINE_MARGIN + m_denominator_layout->size().height;
   return s;
 }
 
 ExpressionLayout * FractionLayout::child(uint16_t index) {
   switch (index) {
     case 0:
-      return m_numerator;
+      return m_numerator_layout;
     case 1:
-      return m_denominator;
+      return m_denominator_layout;
     default:
       return nullptr;
   }
@@ -50,12 +51,12 @@ ExpressionLayout * FractionLayout::child(uint16_t index) {
 
 KDPoint FractionLayout::positionOfChild(ExpressionLayout * child) {
   KDPoint p;
-  if (child == m_numerator) {
-    p.x = (KDCoordinate)((size().width - m_numerator->size().width)/2);
+  if (child == m_numerator_layout) {
+    p.x = (KDCoordinate)((size().width - m_numerator_layout->size().width)/2);
     p.y = 0;
-  } else if (child == m_denominator) {
-    p.x = (KDCoordinate)((size().width - m_denominator->size().width)/2);
-    p.y = (KDCoordinate)(m_numerator->size().height + 2*FRACTION_LINE_MARGIN + FRACTION_LINE_HEIGHT);
+  } else if (child == m_denominator_layout) {
+    p.x = (KDCoordinate)((size().width - m_denominator_layout->size().width)/2);
+    p.y = (KDCoordinate)(m_numerator_layout->size().height + 2*FRACTION_LINE_MARGIN + FRACTION_LINE_HEIGHT);
   } else {
     assert(false); // Should not happen
   }
diff --git a/poincare/src/layout/fraction_layout.h b/poincare/src/layout/fraction_layout.h
index 56e531d64..5d1953ab8 100644
--- a/poincare/src/layout/fraction_layout.h
+++ b/poincare/src/layout/fraction_layout.h
@@ -6,7 +6,7 @@
 
 class FractionLayout : public ExpressionLayout {
   public:
-    FractionLayout(ExpressionLayout * parent, Expression * numerator, Expression * denominator);
+    FractionLayout(ExpressionLayout * numerator, ExpressionLayout * denominator);
     ~FractionLayout();
   protected:
     void render(KDPoint point) override;
@@ -14,8 +14,8 @@ class FractionLayout : public ExpressionLayout {
     ExpressionLayout * child(uint16_t index) override;
     KDPoint positionOfChild(ExpressionLayout * child) override;
   private:
-    ExpressionLayout * m_numerator;
-    ExpressionLayout * m_denominator;
+    ExpressionLayout * m_numerator_layout;
+    ExpressionLayout * m_denominator_layout;
 };
 
 #endif
diff --git a/poincare/src/layout/function_layout.cpp b/poincare/src/layout/function_layout.cpp
deleted file mode 100644
index 02bc5410b..000000000
--- a/poincare/src/layout/function_layout.cpp
+++ /dev/null
@@ -1,73 +0,0 @@
-extern "C" {
-#include <kandinsky.h>
-#include <assert.h>
-}
-#include "function_layout.h"
-#include "string_layout.h"
-
-// This code seems like a duplicate of the horizontal layout but it isn't, indeed the horizontal
-// layout is used to print the same operation applied to different expressions such that:
-//   "expr_1 + epr_2 + expr_3 + expr_4".
-// Here we want the pattern
-//   FUNCTION_NAME(expr).
-// Thus the code in horizontal layer is not really reusable.
-
-FunctionLayout::FunctionLayout(ExpressionLayout * parent, char* function_name, Expression * argument) :
-ExpressionLayout(parent) {
-  m_children[0] = new StringLayout(this, function_name, 1);
-
-  char string[2] = {'(', '\0'};
-  m_children[1] = new StringLayout(this, string, 1);
-
-  m_children[2] = argument->createLayout(this);
-
-  string[0] = ')';
-  m_children[3] = new StringLayout(this, string, 1);
-}
-
-FunctionLayout::~FunctionLayout() {
-  for (int i(0); i<4; i++) {
-    delete m_children[i];
-  }
-}
-
-void FunctionLayout::render(KDPoint point) { }
-
-KDSize FunctionLayout::computeSize() {
-  KDSize size = (KDSize){.width = 0, .height = 0};
-  int i = 0;
-  while (ExpressionLayout * c = child(i++)) {
-    KDSize childSize = c->size();
-    size.width += childSize.width;
-    if (childSize.height > size.height) {
-      size.height = childSize.height;
-    }
-  }
-  return size;
-}
-
-ExpressionLayout * FunctionLayout::child(uint16_t index) {
-  if (index >= 4) {
-    return nullptr;
-  }
-  return m_children[index];
-}
-
-KDPoint FunctionLayout::positionOfChild(ExpressionLayout * child) {
-  KDPoint position = (KDPoint){.x = 0, .y = 0};
-  uint16_t index = 0;
-  for (int i=0;i<4;i++) {
-    if (m_children[i] == child) {
-      index = i;
-      break;
-    }
-  }
-  if (index > 0) {
-    ExpressionLayout * previousChild = m_children[index-1];
-    assert(previousChild != nullptr);
-    position.x = previousChild->origin().x + previousChild->size().width;
-  }
-  position.y = (size().height - child->size().height)/2;
-  return position;
-}
-
diff --git a/poincare/src/layout/function_layout.h b/poincare/src/layout/function_layout.h
deleted file mode 100644
index 0b689dfcf..000000000
--- a/poincare/src/layout/function_layout.h
+++ /dev/null
@@ -1,21 +0,0 @@
-#ifndef POINCARE_FUNCTION_LAYOUT_H
-#define POINCARE_FUNCTION_LAYOUT_H
-
-#include <poincare/expression.h>
-#include <poincare/expression_layout.h>
-
-class FunctionLayout : public ExpressionLayout {
-  public:
-    FunctionLayout(ExpressionLayout * parent, char* function_name, Expression * arg);
-    ~FunctionLayout();
-  protected:
-    void render(KDPoint point) override;
-    KDSize computeSize() override;
-    ExpressionLayout * child(uint16_t index) override;
-    KDPoint positionOfChild(ExpressionLayout * child) override;
-  private:
-    ExpressionLayout * m_children[4];
-};
-
-#endif
-
diff --git a/poincare/src/layout/horizontal_layout.cpp b/poincare/src/layout/horizontal_layout.cpp
index eebc343b0..2b43b7685 100644
--- a/poincare/src/layout/horizontal_layout.cpp
+++ b/poincare/src/layout/horizontal_layout.cpp
@@ -6,15 +6,11 @@ extern "C" {
 #include "horizontal_layout.h"
 #include "string_layout.h"
 
-HorizontalLayout::HorizontalLayout(ExpressionLayout * parent, Expression ** operands,int number_of_operands, char symbol) : ExpressionLayout(parent) {
-  assert(number_of_operands > 0);
-  m_number_of_children = 2*number_of_operands-1;
-  m_children_layouts = (ExpressionLayout **)malloc(m_number_of_children*sizeof(ExpressionLayout *));
-  char string[2] = {symbol, '\0'};
-  m_children_layouts[0] = operands[0]->createLayout(this);
-  for (int i=1; i<number_of_operands; i++) {
-    m_children_layouts[2*i-1] = new StringLayout(this, string, 1);
-    m_children_layouts[2*i] = operands[i]->createLayout(this);
+HorizontalLayout::HorizontalLayout(ExpressionLayout ** children_layouts, int number_of_children) :
+  ExpressionLayout(), m_number_of_children(number_of_children), m_children_layouts(children_layouts) {
+  assert(number_of_children > 0);
+  for (int i=0; i<m_number_of_children; i++) {
+    m_children_layouts[i]->setParent(this);
   }
 }
 
@@ -41,8 +37,8 @@ KDSize HorizontalLayout::computeSize() {
 }
 
 ExpressionLayout * HorizontalLayout::child(uint16_t index) {
-  assert(index <= m_number_of_children);
-  if (index < m_number_of_children) {
+  assert(index <= (unsigned int) m_number_of_children);
+  if (index < (unsigned int) m_number_of_children) {
     return m_children_layouts[index];
   } else {
     return nullptr;
diff --git a/poincare/src/layout/horizontal_layout.h b/poincare/src/layout/horizontal_layout.h
index 0ee133f5c..44468fc7b 100644
--- a/poincare/src/layout/horizontal_layout.h
+++ b/poincare/src/layout/horizontal_layout.h
@@ -6,7 +6,7 @@
 
 class HorizontalLayout : public ExpressionLayout {
   public:
-    HorizontalLayout(ExpressionLayout * parent, Expression ** operands, int number_of_children, char symbol);
+    HorizontalLayout(ExpressionLayout ** layouts, int number_of_children);
     ~HorizontalLayout();
   protected:
     void render(KDPoint point) override;
diff --git a/poincare/src/layout/string_layout.cpp b/poincare/src/layout/string_layout.cpp
index ec65e22e3..52de8df98 100644
--- a/poincare/src/layout/string_layout.cpp
+++ b/poincare/src/layout/string_layout.cpp
@@ -2,8 +2,8 @@
 #include <stdlib.h>
 #include "string_layout.h"
 
-StringLayout::StringLayout(ExpressionLayout * parent, const char * string, size_t length) :
-ExpressionLayout(parent) {
+StringLayout::StringLayout(const char * string, size_t length) :
+ExpressionLayout() {
   assert(string[length] == 0); // Assert NULL-termination
   m_string = (char *)malloc(sizeof(char)*(length+1));
   memcpy(m_string, string, (length+1));
diff --git a/poincare/src/layout/string_layout.h b/poincare/src/layout/string_layout.h
index b70afcd40..0c5de9546 100644
--- a/poincare/src/layout/string_layout.h
+++ b/poincare/src/layout/string_layout.h
@@ -6,7 +6,7 @@
 
 class StringLayout : public ExpressionLayout {
   public:
-    StringLayout(ExpressionLayout * parent, const char * string, size_t length);
+    StringLayout(const char * string, size_t length);
     ~StringLayout();
   protected:
     void render(KDPoint point) override;
diff --git a/poincare/src/power.cpp b/poincare/src/power.cpp
index d9c53835d..6eb6cb2f4 100644
--- a/poincare/src/power.cpp
+++ b/poincare/src/power.cpp
@@ -14,6 +14,6 @@ Expression::Type Power::type() {
   return Expression::Type::Power;
 }
 
-ExpressionLayout * Power::createLayout(ExpressionLayout * parent) {
-  return new ExponentLayout(parent, m_operands[0], m_operands[1]);
+ExpressionLayout * Power::createLayout() {
+  return new ExponentLayout(m_operands[0]->createLayout(), m_operands[1]->createLayout());
 }
diff --git a/poincare/src/product.cpp b/poincare/src/product.cpp
index 36c93dcba..7fefa4ca1 100644
--- a/poincare/src/product.cpp
+++ b/poincare/src/product.cpp
@@ -16,6 +16,6 @@ Expression::Type Product::type() {
   return Expression::Type::Product;
 }
 
-ExpressionLayout * Product::createLayout(ExpressionLayout * parent) {
-  return new HorizontalLayout(parent, m_operands, m_numberOfOperands, '*');
+char Product::operatorChar() {
+  return '*';
 }
diff --git a/poincare/src/subtraction.cpp b/poincare/src/subtraction.cpp
index 448553f2a..ced5648c6 100644
--- a/poincare/src/subtraction.cpp
+++ b/poincare/src/subtraction.cpp
@@ -1,5 +1,9 @@
+extern "C" {
+#include <stdlib.h>
+}
 #include <poincare/subtraction.h>
 #include "layout/horizontal_layout.h"
+#include "layout/string_layout.h"
 
 Expression * Subtraction::clone() {
   return new Subtraction(m_operands, true);
@@ -13,6 +17,11 @@ Expression::Type Subtraction::type() {
   return Expression::Type::Subtraction;
 }
 
-ExpressionLayout * Subtraction::createLayout(ExpressionLayout * parent) {
-  return new HorizontalLayout(parent, m_operands, 2, '-');
+ExpressionLayout * Subtraction::createLayout() {
+  ExpressionLayout** children_layouts = (ExpressionLayout **)malloc(3*sizeof(ExpressionLayout *));
+  children_layouts[0] = m_operands[0]->createLayout();
+  char string[2] = {'-', '\0'};
+  children_layouts[1] = new StringLayout(string, 1);
+  children_layouts[2] = m_operands[1]->createLayout();
+  return new HorizontalLayout(children_layouts, 3);
 }
diff --git a/poincare/src/symbol.cpp b/poincare/src/symbol.cpp
index a47b349e0..ca8c3f05f 100644
--- a/poincare/src/symbol.cpp
+++ b/poincare/src/symbol.cpp
@@ -25,9 +25,9 @@ Expression::Type Symbol::type() {
   return Expression::Type::Symbol;
 }
 
-ExpressionLayout * Symbol::createLayout(ExpressionLayout * parent) {
+ExpressionLayout * Symbol::createLayout() {
   size_t length = strlen(m_name);
-  return new StringLayout(parent, m_name, length);
+  return new StringLayout(m_name, length);
 }
 
 Expression * Symbol::clone() {