diff --git a/poincare/include/poincare/dynamic_layout_hierarchy.h b/poincare/include/poincare/dynamic_layout_hierarchy.h
index ec698cd46..8099c50ef 100644
--- a/poincare/include/poincare/dynamic_layout_hierarchy.h
+++ b/poincare/include/poincare/dynamic_layout_hierarchy.h
@@ -23,8 +23,10 @@ public:
   int numberOfChildren() const override { return m_numberOfChildren; }
   const ExpressionLayout * const * children() const override { return m_children; };
 
+  void addNonEmptyChildrenAtIndex(const ExpressionLayout * const * operands, int numberOfOperands, int indexForInsertion);
   bool addChildAtIndex(ExpressionLayout * operand, int index) override;
   void removeChildAtIndex(int index, bool deleteAfterRemoval) override;
+  void mergeChildrenAtIndex(DynamicLayoutHierarchy * eL, int index); // WITHOUT delete.
 
   bool isEmpty() const override;
 protected:
diff --git a/poincare/include/poincare/expression_layout.h b/poincare/include/poincare/expression_layout.h
index e39253317..1277db657 100644
--- a/poincare/include/poincare/expression_layout.h
+++ b/poincare/include/poincare/expression_layout.h
@@ -50,6 +50,8 @@ public:
   ExpressionLayout * replaceWithJuxtapositionOf(ExpressionLayout * leftChild, ExpressionLayout * rightChild, bool deleteAfterReplace);
   virtual void replaceChild(const ExpressionLayout * oldChild, ExpressionLayout * newChild, bool deleteOldChild = true);
   void detachChild(const ExpressionLayout * e); // Removes a child WITHOUT deleting it
+  void detachChildren(); //Removes all children WITHOUT deleting them
+
 
   /* Dynamic Layout*/
   virtual bool addChildAtIndex(ExpressionLayout * child, int index) { return false; }
diff --git a/poincare/src/layout/dynamic_layout_hierarchy.cpp b/poincare/src/layout/dynamic_layout_hierarchy.cpp
index f2cea1145..707383ed4 100644
--- a/poincare/src/layout/dynamic_layout_hierarchy.cpp
+++ b/poincare/src/layout/dynamic_layout_hierarchy.cpp
@@ -42,6 +42,40 @@ DynamicLayoutHierarchy::~DynamicLayoutHierarchy() {
   delete[] m_children;
 }
 
+void DynamicLayoutHierarchy::mergeChildrenAtIndex(DynamicLayoutHierarchy * eL, int index) {
+  int indexOfEL = indexOfChild(eL);
+  if (indexOfEL >= 0) {
+    removeChildAtIndex(indexOfEL, false);
+  }
+  addNonEmptyChildrenAtIndex(eL->children(), eL->numberOfChildren(), index);
+  eL->detachChildren();
+  delete eL;
+}
+
+void DynamicLayoutHierarchy::addNonEmptyChildrenAtIndex(const ExpressionLayout * const * operands, int numberOfOperands, int indexForInsertion) {
+  assert(numberOfOperands > 0);
+  const ExpressionLayout ** newOperands = new const ExpressionLayout * [m_numberOfChildren+numberOfOperands];
+  int currentIndex = 0;
+  assert(indexForInsertion <= m_numberOfChildren);
+  for (int i=0; i<indexForInsertion; i++) {
+    newOperands[currentIndex++] = m_children[i];
+  }
+  for (int i=0; i<numberOfOperands; i++) {
+    if (!operands[i]->isEmpty()
+        || (i < numberOfOperands-1 && operands[i+1]->mustHaveLeftBrother()))
+    {
+      const_cast<ExpressionLayout *>(operands[i])->setParent(this);
+      newOperands[currentIndex++] = operands[i];
+    }
+  }
+  for (int i=indexForInsertion; i<m_numberOfChildren; i++) {
+    newOperands[currentIndex++] = m_children[i];
+  }
+  delete[] m_children;
+  m_children = newOperands;
+  m_numberOfChildren = currentIndex;
+}
+
 bool DynamicLayoutHierarchy::addChildAtIndex(ExpressionLayout * child, int index) {
   assert(index >= 0 && index <= m_numberOfChildren);
   const ExpressionLayout ** newChildren = new const ExpressionLayout * [m_numberOfChildren+1];
diff --git a/poincare/src/layout/expression_layout.cpp b/poincare/src/layout/expression_layout.cpp
index f3598d780..845ab35fd 100644
--- a/poincare/src/layout/expression_layout.cpp
+++ b/poincare/src/layout/expression_layout.cpp
@@ -197,6 +197,12 @@ void ExpressionLayout::detachChild(const ExpressionLayout * e) {
   }
 }
 
+void ExpressionLayout::detachChildren() {
+  for (int i = 0; i  <numberOfChildren(); i++) {
+    detachChildAtIndex(i);
+  }
+}
+
 void ExpressionLayout::removeChildAtIndex(int index, bool deleteAfterRemoval) {
   assert(index >= 0 && index < numberOfChildren());
   replaceChild(editableChild(index), new EmptyVisibleLayout(), deleteAfterRemoval);
diff --git a/poincare/src/layout/horizontal_layout.cpp b/poincare/src/layout/horizontal_layout.cpp
index f0a627346..0840332aa 100644
--- a/poincare/src/layout/horizontal_layout.cpp
+++ b/poincare/src/layout/horizontal_layout.cpp
@@ -50,7 +50,7 @@ void HorizontalLayout::replaceChild(const ExpressionLayout * oldChild, Expressio
   // new layout then destroy it.
   if (newChild->isHorizontal()) {
     int indexForInsertion = indexOfChild(const_cast<ExpressionLayout *>(oldChild));
-    mergeChildrenAtIndex(newChild, indexForInsertion + 1);
+    mergeChildrenAtIndex(static_cast<HorizontalLayout *>(newChild), indexForInsertion + 1);
     removeChildAtIndex(indexForInsertion, deleteOldChild);
     return;
   }
@@ -65,11 +65,10 @@ void HorizontalLayout::addOrMergeChildAtIndex(ExpressionLayout * eL, int index)
     newIndex = index == 0 ? 0 : index - 1;
   }
   if (eL->isHorizontal()) {
-    mergeChildrenAtIndex(eL, newIndex);
+    mergeChildrenAtIndex(static_cast<HorizontalLayout *>(eL), newIndex);
     return;
   }
   addChildAtIndex(eL, newIndex);
-
 }
 
 bool HorizontalLayout::moveLeft(ExpressionLayoutCursor * cursor) {
@@ -228,27 +227,6 @@ KDPoint HorizontalLayout::positionOfChild(ExpressionLayout * child) {
   return KDPoint(x, y);
 }
 
-void HorizontalLayout::mergeChildrenAtIndex(ExpressionLayout * eL, int index) {
-  int indexOfEL = indexOfChild(eL);
-  if (indexOfEL >= 0) {
-    removeChildAtIndex(indexOfEL, false);
-  }
-  int numChildren = eL->numberOfChildren();
-  int currentAdditionIndex = index;
-  for (int i = 0; i < numChildren; i++) {
-    ExpressionLayout * currentChild = eL->editableChild(i);
-    // Do not add empty children if we can
-    if (!currentChild->isEmpty()
-        || i == numChildren - 1
-        || (i < numChildren - 1 && eL->editableChild(i+1)->mustHaveLeftBrother()))
-    {
-      addChildAtIndex(currentChild, currentAdditionIndex++);
-      eL->detachChild(currentChild);
-    }
-  }
-  delete eL;
-}
-
 bool HorizontalLayout::moveVertically(ExpressionLayout::VerticalDirection direction, ExpressionLayoutCursor * cursor, ExpressionLayout * previousLayout, ExpressionLayout * previousPreviousLayout) {
   // Prevent looping fom child to parent
   if (previousPreviousLayout == this) {
diff --git a/poincare/src/layout/horizontal_layout.h b/poincare/src/layout/horizontal_layout.h
index 209fda198..223263b22 100644
--- a/poincare/src/layout/horizontal_layout.h
+++ b/poincare/src/layout/horizontal_layout.h
@@ -38,7 +38,6 @@ protected:
   KDSize computeSize() override;
   void computeBaseline() override;
   KDPoint positionOfChild(ExpressionLayout * child) override;
-  void mergeChildrenAtIndex(ExpressionLayout * eL, int index); // WITHOUT delete.
 private:
   bool moveVertically(ExpressionLayout::VerticalDirection direction, ExpressionLayoutCursor * cursor, ExpressionLayout * previousLayout, ExpressionLayout * previousPreviousLayout);
 };