[poincare] Sum and Product can specify their variable name

apps/shared.universal.i18n

@@ -50,7 +50,7 @@ PermuteCommandWithArg = "permute(n,r)"
 P = "p"
 Prediction95CommandWithArg = "prediction95(p,n)"
 PredictionCommandWithArg = "prediction(p,n)"
-ProductCommandWithArg = "product(f(n),nmin,nmax)"
+ProductCommandWithArg = "product(f(n),n,nmin,nmax)"
 QuoCommandWithArg = "quo(p,q)"
 RandintCommandWithArg = "randint(a,b)"
 RandomCommandWithArg = "random()"
@@ -65,7 +65,7 @@ Shift = "shift"
 Sigma = "σ"
 SinhCommandWithArg = "sinh(x)"
 SortCommandWithArg = "sort<(L)"
-SumCommandWithArg = "sum(f(n),nmin,nmax)"
+SumCommandWithArg = "sum(f(n),n,nmin,nmax)"
 Sxy = "Σxy"
 TanhCommandWithArg = "tanh(x)"
 TraceCommandWithArg = "trace(M)"

poincare/include/poincare/product.h

@@ -19,7 +19,7 @@ public:
 private:
   const char * name() const override { return "product"; }
   float emptySequenceValue() const override { return 1.0f; }
-  Layout createSequenceLayout(Layout argumentLayout, Layout subscriptLayout, Layout superscriptLayout) const override;
+  Layout createSequenceLayout(Layout argumentLayout, Layout symbolLayout, Layout subscriptLayout, Layout superscriptLayout) const override;
   Evaluation<double> evaluateWithNextTerm(DoublePrecision p, Evaluation<double> a, Evaluation<double> b) const override {
     return templatedApproximateWithNextTerm<double>(a, b);
   }
@@ -34,10 +34,11 @@ friend class ProductNode;
 public:
   Product();
   Product(const ProductNode * n) : Expression(n) {}
-  Product(Expression operand0, Expression operand1, Expression operand2) : Product() {
+  Product(Expression operand0, Expression operand1, Expression operand2, Expression op) : Product() {
     replaceChildAtIndexInPlace(0, operand0);
     replaceChildAtIndexInPlace(1, operand1);
     replaceChildAtIndexInPlace(2, operand2);
+    replaceChildAtIndexInPlace(3, operand2);
   }
 };
 

poincare/include/poincare/product_layout.h

@@ -25,12 +25,13 @@ private:
 
 class ProductLayout final : public Layout {
 public:
-  ProductLayout(Layout argument, Layout lowerB, Layout upperB) :
+  ProductLayout(Layout argument, Layout variable, Layout lowerB, Layout upperB) :
     Layout(TreePool::sharedPool()->createTreeNode<ProductLayoutNode>())
   {
     replaceChildAtIndexInPlace(0, argument);
-    replaceChildAtIndexInPlace(1, lowerB);
-    replaceChildAtIndexInPlace(2, upperB);
+    replaceChildAtIndexInPlace(1, variable);
+    replaceChildAtIndexInPlace(2, lowerB);
+    replaceChildAtIndexInPlace(3, upperB);
   }
 };
 

poincare/include/poincare/sequence.h

@@ -10,13 +10,13 @@ namespace Poincare {
 
 class SequenceNode : public ExpressionNode {
 public:
-  int numberOfChildren() const override { return 3; }
+  int numberOfChildren() const override { return 4; }
 private:
   Layout createLayout(Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override;
   int serialize(char * buffer, int bufferSize, Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override {
     return SerializationHelper::Prefix(this, buffer, bufferSize, floatDisplayMode, numberOfSignificantDigits, name());
   }
-  virtual Layout createSequenceLayout(Layout subscriptLayout, Layout superscriptLayout, Layout argumentLayout) const = 0;
+  virtual Layout createSequenceLayout(Layout argumentLayout, Layout symbolLayout, Layout subscriptLayout, Layout superscriptLayout) const = 0;
   virtual const char * name() const = 0;
   /* Approximation */
   Evaluation<float> approximate(SinglePrecision p, Context& context, Preferences::AngleUnit angleUnit) const override { return templatedApproximate<float>(context, angleUnit); }

poincare/include/poincare/sequence_layout.h

@@ -23,15 +23,15 @@ public:
   char XNTChar() const override { return 'n'; }
 
   // TreeNode
-  int numberOfChildren() const override { return 3; }
+  int numberOfChildren() const override { return 4; }
 
 protected:
   constexpr static KDCoordinate k_boundHeightMargin = 2;
   constexpr static KDCoordinate k_argumentWidthMargin = 2;
   constexpr static const KDFont * k_font = KDFont::LargeFont;
-  constexpr static char k_nEquals[] = {'n', '=', 0};
+  constexpr static char k_equal[] = {'=', 0};
 
-  KDSize lowerBoundSizeWithNEquals();
+  KDSize lowerBoundSizeWithVariableEquals();
 
   // LayoutNode
   KDSize computeSize() override;
@@ -40,9 +40,13 @@ protected:
 
   int writeDerivedClassInBuffer(const char * operatorName, char * buffer, int bufferSize, Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const;
   LayoutNode * argumentLayout() { return childAtIndex(0); }
-  LayoutNode * lowerBoundLayout() { return childAtIndex(1); }
-  LayoutNode * upperBoundLayout() { return childAtIndex(2); }
+  LayoutNode * variableLayout() { return childAtIndex(1); }
+  LayoutNode * lowerBoundLayout() { return childAtIndex(2); }
+  LayoutNode * upperBoundLayout() { return childAtIndex(3); }
   void render(KDContext * ctx, KDPoint p, KDColor expressionColor, KDColor backgroundColor) override;
+private:
+  KDCoordinate completeLowerBoundX();
+  KDCoordinate subscriptBaseline();
 };
 
 }

poincare/include/poincare/sum.h

@@ -19,7 +19,7 @@ public:
 private:
   const char * name() const override { return "sum"; }
   float emptySequenceValue() const override { return 0.0f; }
-  Layout createSequenceLayout(Layout argumentLayout, Layout subscriptLayout, Layout superscriptLayout) const override;
+  Layout createSequenceLayout(Layout argumentLayout, Layout symbolLayout, Layout subscriptLayout, Layout superscriptLayout) const override;
   Evaluation<double> evaluateWithNextTerm(DoublePrecision p, Evaluation<double> a, Evaluation<double> b) const override {
     return templatedApproximateWithNextTerm<double>(a, b);
   }
@@ -34,10 +34,11 @@ friend class SumNode;
 public:
   Sum();
   Sum(const SumNode * n) : Expression(n) {}
-  Sum(Expression operand0, Expression operand1, Expression operand2) : Sum() {
+  Sum(Expression operand0, Expression operand1, Expression operand2, Expression operand3) : Sum() {
     replaceChildAtIndexInPlace(0, operand0);
     replaceChildAtIndexInPlace(1, operand1);
     replaceChildAtIndexInPlace(2, operand2);
+    replaceChildAtIndexInPlace(3, operand3);
   }
 };
 

poincare/include/poincare/sum_layout.h

@@ -23,12 +23,13 @@ private:
 
 class SumLayout final : public Layout {
 public:
-  SumLayout(Layout argument, Layout lowerB, Layout upperB) :
+  SumLayout(Layout argument, Layout variable, Layout lowerB, Layout upperB) :
     Layout(TreePool::sharedPool()->createTreeNode<SumLayoutNode>())
   {
     replaceChildAtIndexInPlace(0, argument);
-    replaceChildAtIndexInPlace(1, lowerB);
-    replaceChildAtIndexInPlace(2, upperB);
+    replaceChildAtIndexInPlace(1, variable);
+    replaceChildAtIndexInPlace(2, lowerB);
+    replaceChildAtIndexInPlace(3, upperB);
   }
 };
 

poincare/src/expression_lexer.l

@@ -115,7 +115,7 @@ atanh { *yylval = HyperbolicArcTangent(); return FUNCTION; }
 binomial { *yylval = BinomialCoefficient(); return FUNCTION; }
 ceil { *yylval = Ceiling(); return FUNCTION; }
 confidence { *yylval = ConfidenceInterval(); return FUNCTION; }
-diff { *yylval = Derivative(); return DIFF_FUNCTION; }
+diff { *yylval = Derivative(); return VARIABLE_DEPENDENT_FUNCTION; }
 dim { *yylval = MatrixDimension(); return FUNCTION; }
 conj { *yylval = Conjugate(); return FUNCTION; }
 det { *yylval = Determinant(); return FUNCTION; }
@@ -126,7 +126,7 @@ floor { *yylval = Floor(); return FUNCTION; }
 frac { *yylval = FracPart(); return FUNCTION; }
 gcd { *yylval = GreatCommonDivisor(); return FUNCTION; }
 im { *yylval = ImaginaryPart(); return FUNCTION; }
-int { *yylval = Integral(); return INT_FUNCTION; }
+int { *yylval = Integral(); return VARIABLE_DEPENDENT_FUNCTION; }
 inverse { *yylval = MatrixInverse(); return FUNCTION; }
 lcm { *yylval = LeastCommonMultiple(); return FUNCTION; }
 ln { *yylval = NaperianLogarithm(); return FUNCTION; }
@@ -135,7 +135,7 @@ log\_\{ { return LOG_FUNCTION_TWO_ARGUMENTS; }
 permute { *yylval = PermuteCoefficient(); return FUNCTION; }
 prediction95 { *yylval = PredictionInterval(); return FUNCTION; }
 prediction { *yylval = SimplePredictionInterval(); return FUNCTION; }
-product { *yylval = Product(); return FUNCTION; }
+product { *yylval = Product(); return VARIABLE_DEPENDENT_FUNCTION; }
 quo { *yylval = DivisionQuotient(); return FUNCTION; }
 random { *yylval = Random(); return FUNCTION; }
 randint { *yylval = Randint(); return FUNCTION; }
@@ -145,7 +145,7 @@ root { *yylval = NthRoot(); return FUNCTION; }
 round { *yylval = Round(); return FUNCTION; }
 sin { *yylval = Sine(); return FUNCTION; }
 sinh { *yylval = HyperbolicSine(); return FUNCTION; }
-sum { *yylval = Sum(); return FUNCTION; }
+sum { *yylval = Sum(); return VARIABLE_DEPENDENT_FUNCTION; }
 tan { *yylval = Tangent(); return FUNCTION; }
 tanh { *yylval = HyperbolicTangent(); return FUNCTION; }
 trace { *yylval = MatrixTrace(); return FUNCTION; }

poincare/src/expression_parser.y

@@ -73,7 +73,7 @@ using namespace Poincare;
 %nonassoc RIGHT_BRACKET
 %nonassoc LEFT_BRACE
 %nonassoc RIGHT_BRACE
-%nonassoc FUNCTION LOG_FUNCTION LOG_FUNCTION_TWO_ARGUMENTS DIFF_FUNCTION INT_FUNCTION
+%nonassoc FUNCTION LOG_FUNCTION LOG_FUNCTION_TWO_ARGUMENTS VARIABLE_DEPENDENT_FUNCTION
 %left COMMA
 %nonassoc UNDERSCORE
 %nonassoc DIGITS
@@ -134,8 +134,7 @@ term   : TERM   { $$ = $1; }
 /* Special case for logarithm, as we do not at first if it needs 1 or 2 children */
        | LOG_FUNCTION lstData RIGHT_PARENTHESIS { if ($2.numberOfChildren() == 1) { $$ = Logarithm($2.childAtIndex(0)); } else if ($2.numberOfChildren() == 2) { $$ = Logarithm($2.childAtIndex(0), $2.childAtIndex(1));} else { YYERROR; } ; }
        | LOG_FUNCTION_TWO_ARGUMENTS exp RIGHT_BRACE LEFT_PARENTHESIS exp RIGHT_PARENTHESIS { $$ = Logarithm($5, $2); }
-       | DIFF_FUNCTION LEFT_PARENTHESIS lstData RIGHT_PARENTHESIS { if ($$.numberOfChildren() != ($3.numberOfChildren())) { YYERROR; } ; if ($3.childAtIndex(1).type() != ExpressionNode::Type::Symbol) { YYERROR; } ; $$ = $1; $$.setChildrenInPlace($3); }
-       | INT_FUNCTION LEFT_PARENTHESIS lstData RIGHT_PARENTHESIS { if ($$.numberOfChildren() != ($3.numberOfChildren())) { YYERROR; } ; if ($3.childAtIndex(1).type() != ExpressionNode::Type::Symbol && $3.childAtIndex(1).type() != ExpressionNode::Type::EmptyExpression ) { YYERROR; } ; $$ = $1; $$.setChildrenInPlace($3); }
+       | VARIABLE_DEPENDENT_FUNCTION LEFT_PARENTHESIS lstData RIGHT_PARENTHESIS { if ($$.numberOfChildren() != ($3.numberOfChildren())) { YYERROR; } ; if ($3.childAtIndex(1).type() != ExpressionNode::Type::Symbol && $3.childAtIndex(1).type() != ExpressionNode::Type::EmptyExpression ) { YYERROR; } ; $$ = $1; $$.setChildrenInPlace($3); }
        | LEFT_PARENTHESIS exp RIGHT_PARENTHESIS { $$ = Parenthesis($2); }
 /* MATRICES_ARE_DEFINED */
        | LEFT_BRACKET mtxData RIGHT_BRACKET { $$ = $2; }

poincare/src/product.cpp

@@ -9,8 +9,8 @@ extern "C" {
 
 namespace Poincare {
 
-Layout ProductNode::createSequenceLayout(Layout argumentLayout, Layout subscriptLayout, Layout superscriptLayout) const {
-  return ProductLayout(argumentLayout, subscriptLayout, superscriptLayout);
+Layout ProductNode::createSequenceLayout(Layout argumentLayout, Layout symbolLayout, Layout subscriptLayout, Layout superscriptLayout) const {
+  return ProductLayout(argumentLayout, symbolLayout, subscriptLayout, superscriptLayout);
 }
 
 template<typename T>

poincare/src/product_layout.cpp

@@ -13,7 +13,7 @@ int ProductLayoutNode::serialize(char * buffer, int bufferSize, Preferences::Pri
 void ProductLayoutNode::render(KDContext * ctx, KDPoint p, KDColor expressionColor, KDColor backgroundColor) {
   // Compute sizes.
   KDSize upperBoundSize = upperBoundLayout()->layoutSize();
-  KDSize lowerBoundNEqualsSize = lowerBoundSizeWithNEquals();
+  KDSize lowerBoundNEqualsSize = lowerBoundSizeWithVariableEquals();
 
   // Render the Product symbol.
   ctx->fillRect(KDRect(p.x() + max(max(0, (upperBoundSize.width()-k_symbolWidth)/2), (lowerBoundNEqualsSize.width()-k_symbolWidth)/2),

poincare/src/sequence.cpp

@@ -12,19 +12,19 @@ extern "C" {
 namespace Poincare {
 
 Layout SequenceNode::createLayout(Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const {
-  return createSequenceLayout(childAtIndex(0)->createLayout(floatDisplayMode, numberOfSignificantDigits), childAtIndex(1)->createLayout(floatDisplayMode, numberOfSignificantDigits), childAtIndex(2)->createLayout(floatDisplayMode, numberOfSignificantDigits));
+  return createSequenceLayout(childAtIndex(0)->createLayout(floatDisplayMode, numberOfSignificantDigits), childAtIndex(1)->createLayout(floatDisplayMode, numberOfSignificantDigits), childAtIndex(2)->createLayout(floatDisplayMode, numberOfSignificantDigits), childAtIndex(3)->createLayout(floatDisplayMode, numberOfSignificantDigits));
 }
 
 template<typename T>
 Evaluation<T> SequenceNode::templatedApproximate(Context& context, Preferences::AngleUnit angleUnit) const {
-  Evaluation<T> aInput = childAtIndex(1)->approximate(T(), context, angleUnit);
-  Evaluation<T> bInput = childAtIndex(2)->approximate(T(), context, angleUnit);
+  Evaluation<T> aInput = childAtIndex(2)->approximate(T(), context, angleUnit);
+  Evaluation<T> bInput = childAtIndex(3)->approximate(T(), context, angleUnit);
   T start = aInput.toScalar();
   T end = bInput.toScalar();
   if (std::isnan(start) || std::isnan(end) || start != (int)start || end != (int)end || end - start > k_maxNumberOfSteps) {
     return Complex<T>::Undefined();
   }
-  VariableContext nContext = VariableContext("n", &context);
+  VariableContext nContext = VariableContext(static_cast<SymbolNode *>(childAtIndex(1))->name(), &context);
   Evaluation<T> result = Complex<T>((T)emptySequenceValue());
   for (int i = (int)start; i <= (int)end; i++) {
     if (Expression::shouldStopProcessing()) {

poincare/src/sequence_layout.cpp

@@ -9,20 +9,34 @@ namespace Poincare {
 
 static inline KDCoordinate max(KDCoordinate x, KDCoordinate y) { return x > y ? x : y; }
 
-constexpr char SequenceLayoutNode::k_nEquals[];
+constexpr char SequenceLayoutNode::k_equal[];
 
 void SequenceLayoutNode::moveCursorLeft(LayoutCursor * cursor, bool * shouldRecomputeLayout) {
-  if (cursor->position() == LayoutCursor::Position::Left
-      && (cursor->layoutNode() == lowerBoundLayout()
-        || cursor->layoutNode() == upperBoundLayout()))
+  if (cursor->layoutNode() == upperBoundLayout())
   {
-    // Case: Left of the bounds. Go Left of the sequence.
+    assert(cursor->position() == LayoutCursor::Position::Left);
+    // Case: Left of the upper bound. Go Left of the sequence.
     cursor->setLayoutNode(this);
     return;
   }
-  if (cursor->position() == LayoutCursor::Position::Left
-      && cursor->layoutNode() == argumentLayout())
+  if (cursor->layoutNode() == lowerBoundLayout())
   {
+    assert(cursor->position() == LayoutCursor::Position::Left);
+    // Case: Left of the lower bound. Go Right of the variable name.
+    cursor->setLayoutNode(variableLayout());
+    cursor->setPosition(LayoutCursor::Position::Right);
+    return;
+  }
+  if (cursor->layoutNode() == variableLayout())
+  {
+    assert(cursor->position() == LayoutCursor::Position::Left);
+    // Case: Left of the variable name. Go Left of the sequence.
+    cursor->setLayoutNode(this);
+    return;
+  }
+  if (cursor->layoutNode() == argumentLayout())
+  {
+    assert(cursor->position() == LayoutCursor::Position::Left);
     // Case: Left of the argument. Go Right of the lower bound.
     cursor->setLayoutNode(lowerBoundLayout());
     cursor->setPosition(LayoutCursor::Position::Right);
@@ -44,18 +58,26 @@ void SequenceLayoutNode::moveCursorLeft(LayoutCursor * cursor, bool * shouldReco
 }
 
 void SequenceLayoutNode::moveCursorRight(LayoutCursor * cursor, bool * shouldRecomputeLayout) {
-  if (cursor->position() == LayoutCursor::Position::Right
-      && (cursor->layoutNode() == lowerBoundLayout()
-        || cursor->layoutNode() == upperBoundLayout()))
+  if (cursor->layoutNode() == lowerBoundLayout()
+        || cursor->layoutNode() == upperBoundLayout())
   {
+    assert(cursor->position() == LayoutCursor::Position::Right);
     // Case: Right of the bounds. Go Left of the argument.
     cursor->setLayoutNode(argumentLayout());
     cursor->setPosition(LayoutCursor::Position::Left);
     return;
   }
-  if (cursor->position() == LayoutCursor::Position::Right
-      && cursor->layoutNode() == argumentLayout())
+  if (cursor->layoutNode() == variableLayout())
   {
+    assert(cursor->position() == LayoutCursor::Position::Right);
+    // Case: Right of the variable name. Go Left of the lower bound.
+    cursor->setLayoutNode(lowerBoundLayout());
+    cursor->setPosition(LayoutCursor::Position::Left);
+    return;
+  }
+  if (cursor->layoutNode() == argumentLayout())
+  {
+    assert(cursor->position() == LayoutCursor::Position::Right);
     // Case: Right of the argument. Go Right.
     cursor->setLayoutNode(this);
     return;
@@ -75,8 +97,8 @@ void SequenceLayoutNode::moveCursorRight(LayoutCursor * cursor, bool * shouldRec
 }
 
 void SequenceLayoutNode::moveCursorUp(LayoutCursor * cursor, bool * shouldRecomputeLayout, bool equivalentPositionVisited) {
-  if (cursor->layoutNode()->hasAncestor(lowerBoundLayout(), true)) {
-  // If the cursor is inside the lower bound, move it to the upper bound
+  if (cursor->layoutNode()->hasAncestor(lowerBoundLayout(), true) || cursor->layoutNode()->hasAncestor(variableLayout(), true)) {
+  // If the cursor is inside the lower bound or inside the variable name, move it to the upper bound
     upperBoundLayout()->moveCursorUpInDescendants(cursor, shouldRecomputeLayout);
     return;
   }
@@ -119,16 +141,25 @@ void SequenceLayoutNode::deleteBeforeCursor(LayoutCursor * cursor) {
 
 // Protected
 
+KDSize SequenceLayoutNode::lowerBoundSizeWithVariableEquals() {
+  KDSize variableSize = variableLayout()->layoutSize();
+  KDSize lowerBoundSize = lowerBoundLayout()->layoutSize();
+  KDSize equalSize = k_font->stringSize(k_equal);
+  return KDSize(
+      variableSize.width() + equalSize.width() + lowerBoundSize.width(),
+      subscriptBaseline() + max(max(variableSize.height() - variableLayout()->baseline(), lowerBoundSize.height() - lowerBoundLayout()->baseline()), equalSize.height()/2));
+}
+
 KDSize SequenceLayoutNode::computeSize() {
-  KDSize nEqualslowerBoundSize = lowerBoundSizeWithNEquals();
+  KDSize totalLowerBoundSize = lowerBoundSizeWithVariableEquals();
   KDSize upperBoundSize = upperBoundLayout()->layoutSize();
   KDSize argumentSize = argumentLayout()->layoutSize();
   KDSize argumentSizeWithParentheses = KDSize(
     argumentSize.width() + 2*ParenthesisLayoutNode::ParenthesisWidth(),
     ParenthesisLayoutNode::HeightGivenChildHeight(argumentSize.height()));
   KDSize result = KDSize(
-    max(max(k_symbolWidth, nEqualslowerBoundSize.width()), upperBoundSize.width())+k_argumentWidthMargin+argumentSizeWithParentheses.width(),
-    baseline() + max(k_symbolHeight/2+k_boundHeightMargin+nEqualslowerBoundSize.height(), argumentSizeWithParentheses.height() - argumentLayout()->baseline()));
+    max(max(k_symbolWidth, totalLowerBoundSize.width()), upperBoundSize.width())+k_argumentWidthMargin+argumentSizeWithParentheses.width(),
+    baseline() + max(k_symbolHeight/2+k_boundHeightMargin+totalLowerBoundSize.height(), argumentSizeWithParentheses.height() - argumentLayout()->baseline()));
   return result;
 }
 
@@ -137,21 +168,22 @@ KDCoordinate SequenceLayoutNode::computeBaseline() {
 }
 
 KDPoint SequenceLayoutNode::positionOfChild(LayoutNode * l) {
-  KDSize nEqualslowerBoundSize = lowerBoundSizeWithNEquals();
-  KDSize nEqualsSize = k_font->stringSize(k_nEquals);
+  KDSize variableSize = variableLayout()->layoutSize();
+  KDSize equalSize = k_font->stringSize(k_equal);
   KDSize upperBoundSize = upperBoundLayout()->layoutSize();
   KDCoordinate x = 0;
   KDCoordinate y = 0;
-  if (l == lowerBoundLayout()) {
-    x = nEqualsSize.width() +
-      max(max(0, (k_symbolWidth-nEqualslowerBoundSize.width())/2),
-          (upperBoundSize.width()-nEqualslowerBoundSize.width())/2);
-    y = baseline() + k_symbolHeight/2 + k_boundHeightMargin;
+  if (l == variableLayout()) {
+    x = completeLowerBoundX();
+    y = baseline() + k_symbolHeight/2 + k_boundHeightMargin + subscriptBaseline() - variableLayout()->baseline();
+  } else if (l == lowerBoundLayout()) {
+    x = completeLowerBoundX() + equalSize.width() + variableSize.width();
+    y = baseline() + k_symbolHeight/2 + k_boundHeightMargin + subscriptBaseline() - lowerBoundLayout()->baseline();
   } else if (l == upperBoundLayout()) {
-    x = max(max(0, (k_symbolWidth-upperBoundSize.width())/2), (nEqualslowerBoundSize.width()-upperBoundSize.width())/2);
+    x = max(max(0, (k_symbolWidth-upperBoundSize.width())/2), (lowerBoundSizeWithVariableEquals().width()-upperBoundSize.width())/2);
     y = baseline() - (k_symbolHeight+1)/2- k_boundHeightMargin-upperBoundSize.height();
   } else if (l == argumentLayout()) {
-    x = max(max(k_symbolWidth, nEqualslowerBoundSize.width()), upperBoundSize.width())+k_argumentWidthMargin+ParenthesisLayoutNode::ParenthesisWidth();
+    x = max(max(k_symbolWidth, lowerBoundSizeWithVariableEquals().width()), upperBoundSize.width())+k_argumentWidthMargin+ParenthesisLayoutNode::ParenthesisWidth();
     y = baseline() - argumentLayout()->baseline();
   } else {
     assert(false);
@@ -174,25 +206,16 @@ int SequenceLayoutNode::writeDerivedClassInBuffer(const char * operatorName, cha
   buffer[numberOfChar++] = '(';
   if (numberOfChar >= bufferSize-1) { return bufferSize-1; }
 
-  // Write the argument
-  numberOfChar += const_cast<SequenceLayoutNode *>(this)->argumentLayout()->serialize(buffer+numberOfChar, bufferSize-numberOfChar, floatDisplayMode, numberOfSignificantDigits);
-  if (numberOfChar >= bufferSize-1) { return bufferSize-1; }
-
-  // Write the comma
-  buffer[numberOfChar++] = ',';
-  if (numberOfChar >= bufferSize-1) { return bufferSize-1; }
-
-  // Write the lower bound
-  numberOfChar += const_cast<SequenceLayoutNode *>(this)->lowerBoundLayout()->serialize(buffer+numberOfChar, bufferSize-numberOfChar, floatDisplayMode, numberOfSignificantDigits);
-  if (numberOfChar >= bufferSize-1) { return bufferSize-1; }
-
-  // Write the comma
-  buffer[numberOfChar++] = ',';
-  if (numberOfChar >= bufferSize-1) { return bufferSize-1; }
-
-  // Write the upper bound
-  numberOfChar += const_cast<SequenceLayoutNode *>(this)->upperBoundLayout()->serialize(buffer+numberOfChar, bufferSize-numberOfChar, floatDisplayMode, numberOfSignificantDigits);
-  if (numberOfChar >= bufferSize-1) { return bufferSize-1; }
+    LayoutNode * argLayouts[] = {const_cast<SequenceLayoutNode *>(this)->argumentLayout(), const_cast<SequenceLayoutNode *>(this)->variableLayout(), const_cast<SequenceLayoutNode *>(this)->lowerBoundLayout(), const_cast<SequenceLayoutNode *>(this)->upperBoundLayout()};
+  for (uint8_t i = 0; i < sizeof(argLayouts)/sizeof(argLayouts[0]); i++) {
+    if (i != 0) {
+      // Write the comma
+      buffer[numberOfChar++] = ',';
+      if (numberOfChar >= bufferSize-1) { return bufferSize-1; }
+    }
+    numberOfChar += argLayouts[i]->serialize(buffer+numberOfChar, bufferSize-numberOfChar, floatDisplayMode, numberOfSignificantDigits);
+    if (numberOfChar >= bufferSize-1) { return bufferSize-1; }
+  }
 
   // Write the closing parenthesis
   buffer[numberOfChar++] = ')';
@@ -201,9 +224,10 @@ int SequenceLayoutNode::writeDerivedClassInBuffer(const char * operatorName, cha
 }
 
 void SequenceLayoutNode::render(KDContext * ctx, KDPoint p, KDColor expressionColor, KDColor backgroundColor) {
-  // Render the "n="
-  KDPoint nEqualsPosition = positionOfChild(lowerBoundLayout()).translatedBy(KDPoint(-k_font->stringSize(k_nEquals).width(), 0));
-  ctx->drawString(k_nEquals, p.translatedBy(nEqualsPosition), k_font, expressionColor, backgroundColor);
+  // Render the "="
+  KDSize variableSize = variableLayout()->layoutSize();
+  KDPoint equalPosition = positionOfChild(variableLayout()).translatedBy(KDPoint(variableSize.width(), variableLayout()->baseline()-k_font->stringSize(k_equal).height()/2));
+  ctx->drawString(k_equal, p.translatedBy(equalPosition), k_font, expressionColor, backgroundColor);
 
   // Render the parentheses
   KDCoordinate argumentWithParenthesesHeight = ParenthesisLayoutNode::HeightGivenChildHeight(argumentLayout()->layoutSize().height());
@@ -220,12 +244,14 @@ void SequenceLayoutNode::render(KDContext * ctx, KDPoint p, KDColor expressionCo
   RightParenthesisLayoutNode::RenderWithChildHeight(argumentWithParenthesesHeight, ctx, rightParenthesisPoint, expressionColor, backgroundColor);
 }
 
-KDSize SequenceLayoutNode::lowerBoundSizeWithNEquals() {
-  KDSize lowerBoundSize = lowerBoundLayout()->layoutSize();
-  KDSize nEqualsSize = k_font->stringSize(k_nEquals);
-  return KDSize(
-      nEqualsSize.width() + lowerBoundSize.width(),
-      max(nEqualsSize.height(), lowerBoundSize.height()));
+KDCoordinate SequenceLayoutNode::completeLowerBoundX() {
+  KDSize upperBoundSize = upperBoundLayout()->layoutSize();
+ return max(max(0, (k_symbolWidth-lowerBoundSizeWithVariableEquals().width())/2),
+          (upperBoundSize.width()-lowerBoundSizeWithVariableEquals().width())/2);
+}
+
+KDCoordinate SequenceLayoutNode::subscriptBaseline() {
+  return max(max(variableLayout()->baseline(), lowerBoundLayout()->baseline()), k_font->stringSize(k_equal).height()/2);
 }
 
 }

poincare/src/sum.cpp

@@ -11,8 +11,8 @@ extern "C" {
 namespace Poincare {
 
 
-Layout SumNode::createSequenceLayout(Layout argumentLayout, Layout subscriptLayout, Layout superscriptLayout) const {
-  return SumLayout(argumentLayout, subscriptLayout, superscriptLayout);
+Layout SumNode::createSequenceLayout(Layout argumentLayout, Layout symbolLayout, Layout subscriptLayout, Layout superscriptLayout) const {
+  return SumLayout(argumentLayout, symbolLayout, subscriptLayout, superscriptLayout);
 }
 
 template<typename T>

poincare/src/sum_layout.cpp

@@ -32,7 +32,7 @@ int SumLayoutNode::serialize(char * buffer, int bufferSize, Preferences::PrintFl
 void SumLayoutNode::render(KDContext * ctx, KDPoint p, KDColor expressionColor, KDColor backgroundColor) {
   // Computes sizes.
   KDSize upperBoundSize = upperBoundLayout()->layoutSize();
-  KDSize lowerBoundNEqualsSize = lowerBoundSizeWithNEquals();
+  KDSize lowerBoundNEqualsSize = lowerBoundSizeWithVariableEquals();
 
   // Render the Sum symbol.
   KDColor workingBuffer[k_symbolWidth*k_symbolHeight];