diff --git a/poincare/src/addition.cpp b/poincare/src/addition.cpp
index cb4080b33..15795ee7b 100644
--- a/poincare/src/addition.cpp
+++ b/poincare/src/addition.cpp
@@ -14,6 +14,5 @@ float Addition::operateApproximatevelyOn(float a, float b) {
 }
 
 ExpressionLayout * Addition::createLayout(ExpressionLayout * parent) {
-  //FIXME: There can be more than two operands now! :-)
-  return new HorizontalLayout(parent, operand(0), '+', operand(1));
+  return new HorizontalLayout(parent, m_operands, m_numberOfOperands, '+');
 }
diff --git a/poincare/src/commutative_operation.cpp b/poincare/src/commutative_operation.cpp
index 929908076..37252e0a0 100644
--- a/poincare/src/commutative_operation.cpp
+++ b/poincare/src/commutative_operation.cpp
@@ -30,6 +30,7 @@ int CommutativeOperation::numberOfOperands() {
 }
 
 Expression * CommutativeOperation::operand(int i) {
+  assert(i < m_numberOfOperands);
   return m_operands[i];
 }
 
diff --git a/poincare/src/expression_lexer.l b/poincare/src/expression_lexer.l
index 008e5fca5..4a92ec02c 100644
--- a/poincare/src/expression_lexer.l
+++ b/poincare/src/expression_lexer.l
@@ -42,10 +42,10 @@ class Expression;
 %%
 
 [0-9]+ { yylval->string = yytext; return(INTEGER); }
-[A-Za-z]+ { yylval->string = yytext; return(SYMBOL); }
 sin {return(SINUS);}
 cos {return(COSINUS);}
 tan {return(TANGENT);}
+[A-Za-z]+ { yylval->string = yytext; return(SYMBOL); }
 \+ { return(PLUS); }
 \- { return(MINUS); }
 \* { return(MULTIPLY); }
diff --git a/poincare/src/layout/horizontal_layout.cpp b/poincare/src/layout/horizontal_layout.cpp
index 0ba763f4b..eebc343b0 100644
--- a/poincare/src/layout/horizontal_layout.cpp
+++ b/poincare/src/layout/horizontal_layout.cpp
@@ -1,29 +1,28 @@
 extern "C" {
-#include <kandinsky.h>
 #include <assert.h>
+#include <kandinsky.h>
+#include <stdlib.h>
 }
 #include "horizontal_layout.h"
 #include "string_layout.h"
 
-HorizontalLayout::HorizontalLayout(ExpressionLayout * parent, int number_of_operands, Expression ** operands, char symbol) {
-  m_number_of_operands = number_of_operands;
-  // FIXME: This implementation is not optimal as the operator layout is created and stored a lot of times.
-  // The reason for this is how the layouts are drawn.
-  m_children_layouts = (ExpressionLayout **)malloc((2*m_number_of_operands-)*sizeof(ExpressionLayout *));
-  m_operator_layout = new StringLayout(this, string, 1);
+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'};
-  for (int i=1; i<m_number_of_operands; i++) {
-    m_operands[2*i-1] = m_operator_layout;
-    m_operands[2*i] = operands[i]->createLayout();
+  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() {
-  for (int i(0); i<m_numberOfOperands; i++) {
-    delete m_operands[2*i];
+  for (int i=0; i<m_number_of_children; i++) {
+    delete m_children_layouts[i];
   }
-  free(m_operands);
-  delete m_operator_layout;
+  free(m_children_layouts);
 }
 
 void HorizontalLayout::render(KDPoint point) { }
@@ -42,23 +41,25 @@ KDSize HorizontalLayout::computeSize() {
 }
 
 ExpressionLayout * HorizontalLayout::child(uint16_t index) {
-  if (index >= 2*m_number_of_operands) {
+  assert(index <= m_number_of_children);
+  if (index < m_number_of_children) {
+    return m_children_layouts[index];
+  } else {
     return nullptr;
   }
-  return m_children_layouts[index];
 }
 
 KDPoint HorizontalLayout::positionOfChild(ExpressionLayout * child) {
   KDPoint position = (KDPoint){.x = 0, .y = 0};
   uint16_t index = 0;
-  for (int i=0;i<3;i++) {
-    if (m_children[i] == child) {
+  for (int i=0;i<m_number_of_children;i++) {
+    if (m_children_layouts[i] == child) {
       index = i;
       break;
     }
   }
   if (index > 0) {
-    ExpressionLayout * previousChild = m_children[index-1];
+    ExpressionLayout * previousChild = m_children_layouts[index-1];
     assert(previousChild != nullptr);
     position.x = previousChild->origin().x + previousChild->size().width;
   }
diff --git a/poincare/src/layout/horizontal_layout.h b/poincare/src/layout/horizontal_layout.h
index 4482aca87..0ee133f5c 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, int number_of_operands, Expression ** operands, char symbol);
+    HorizontalLayout(ExpressionLayout * parent, Expression ** operands, int number_of_children, char symbol);
     ~HorizontalLayout();
   protected:
     void render(KDPoint point) override;
@@ -14,9 +14,8 @@ class HorizontalLayout : public ExpressionLayout {
     ExpressionLayout * child(uint16_t index) override;
     KDPoint positionOfChild(ExpressionLayout * child) override;
   private:
-    int m_number_of_operands;
+    int m_number_of_children;
     ExpressionLayout ** m_children_layouts;
-    ExpressionLayout * m_operator_layout;
 };
 
 #endif
diff --git a/poincare/src/product.cpp b/poincare/src/product.cpp
index fc888bfd8..36c93dcba 100644
--- a/poincare/src/product.cpp
+++ b/poincare/src/product.cpp
@@ -17,6 +17,5 @@ Expression::Type Product::type() {
 }
 
 ExpressionLayout * Product::createLayout(ExpressionLayout * parent) {
-  //FIXME: There can be more than two factors now! :-)
-  return new HorizontalLayout(parent, operand(0), '*', operand(1));
+  return new HorizontalLayout(parent, m_operands, m_numberOfOperands, '*');
 }
diff --git a/poincare/src/subtraction.cpp b/poincare/src/subtraction.cpp
index 7f82f02db..448553f2a 100644
--- a/poincare/src/subtraction.cpp
+++ b/poincare/src/subtraction.cpp
@@ -14,5 +14,5 @@ Expression::Type Subtraction::type() {
 }
 
 ExpressionLayout * Subtraction::createLayout(ExpressionLayout * parent) {
-  return new HorizontalLayout(parent, m_operands[0], '-', m_operands[1]);
+  return new HorizontalLayout(parent, m_operands, 2, '-');
 }