[apps/solver] Display user variables in the solutions

2026-03-18 21:30:38 +01:00 · 2020-01-27 17:58:26 +01:00
parent afbca672fd
commit db0e7f0d8b
15 changed files with 198 additions and 70 deletions
--- a/apps/solver/base.de.i18n
+++ b/apps/solver/base.de.i18n
@@ -23,3 +23,7 @@ OnlyFirstSolutionsDisplayed0 = "Es werden nur die ersten"
 OnlyFirstSolutionsDisplayed1 = "zehn Lösungen angezeigt."
 PolynomeHasNoRealSolution0 = "Das Polynom hat"
 PolynomeHasNoRealSolution1 = "keine reelle Nullstelle"
+PredefinedVariablesUsedLeft = "Verwen"
+PredefinedVariablesUsedRight = "dete vordefinierte Variablen"
+PredefinedVariablesIgnoredLeft = "Ignorie"
+PredefinedVariablesIgnoredRight = "rt vordefinierte Variablen"
--- a/apps/solver/base.en.i18n
+++ b/apps/solver/base.en.i18n
@@ -23,3 +23,7 @@ OnlyFirstSolutionsDisplayed0 = "Only the first 10 solutions"
 OnlyFirstSolutionsDisplayed1 = "are displayed"
 PolynomeHasNoRealSolution0 = "The polynomial has no"
 PolynomeHasNoRealSolution1 = "real root"
+PredefinedVariablesUsedLeft = "Used "
+PredefinedVariablesUsedRight = "predefined variables"
+PredefinedVariablesIgnoredLeft = "Ignor"
+PredefinedVariablesIgnoredRight = "ed predefined variables"
--- a/apps/solver/base.es.i18n
+++ b/apps/solver/base.es.i18n
@@ -23,3 +23,7 @@ OnlyFirstSolutionsDisplayed0 = "Sólo se muestran las"
 OnlyFirstSolutionsDisplayed1 = "10 primeras soluciones"
 PolynomeHasNoRealSolution0 = "El polinomio no tiene"
 PolynomeHasNoRealSolution1 = "ninguna raíz real"
+PredefinedVariablesUsedLeft = "Variable"
+PredefinedVariablesUsedRight = "s predefinidas utilizadas"
+PredefinedVariablesIgnoredLeft = "Variable"
+PredefinedVariablesIgnoredRight = "s predefinidas ignoradas"
--- a/apps/solver/base.fr.i18n
+++ b/apps/solver/base.fr.i18n
@@ -23,3 +23,7 @@ OnlyFirstSolutionsDisplayed0 = "Seulement les 10 premières"
 OnlyFirstSolutionsDisplayed1 = "solutions sont affichées"
 PolynomeHasNoRealSolution0 = "Le polynôme n'admet pas"
 PolynomeHasNoRealSolution1 = "de racine réelle"
+PredefinedVariablesUsedLeft = "Variable"
+PredefinedVariablesUsedRight = "s prédéfinies utilisées"
+PredefinedVariablesIgnoredLeft = "Variable"
+PredefinedVariablesIgnoredRight = "s prédéfinies ignorées"
--- a/apps/solver/base.pt.i18n
+++ b/apps/solver/base.pt.i18n
@@ -23,3 +23,7 @@ OnlyFirstSolutionsDisplayed0 = "Somente as 10 primeiras"
 OnlyFirstSolutionsDisplayed1 = "soluções são exibidas"
 PolynomeHasNoRealSolution0 = "O polinômio não tem"
 PolynomeHasNoRealSolution1 = "nenhuma raiz real"
+PredefinedVariablesUsedLeft = "Variáveis "
+PredefinedVariablesUsedRight = "pré-definidas utilizadas"
+PredefinedVariablesIgnoredLeft = "Variáveis"
+PredefinedVariablesIgnoredRight = " pré-definidas ignoradas"
--- a/apps/solver/equation_store.cpp
+++ b/apps/solver/equation_store.cpp
@@ -27,7 +27,8 @@ EquationStore::EquationStore() :
  m_type(Type::LinearSystem),
  m_numberOfSolutions(0),
  m_exactSolutionExactLayouts{},
-  m_exactSolutionApproximateLayouts{}
+  m_exactSolutionApproximateLayouts{},
+  m_numberOfUserVariables(0)
 {
 }

@@ -100,14 +101,15 @@ bool EquationStore::haveMoreApproximationSolutions(Context * context, bool solve
  return !std::isnan(PoincareHelpers::NextRoot(modelForRecord(definedRecordAtIndex(0))->standardForm(context, solveWithoutContext), m_variables[0], m_approximateSolutions[m_numberOfSolutions-1], step, m_intervalApproximateSolutions[1], context));
 }

-void EquationStore::approximateSolve(Poincare::Context * context, bool shouldReplaceFuncionsButNotSymbols) {
+void EquationStore::approximateSolve(Poincare::Context * context, bool shouldReplaceFunctionsButNotSymbols) {
+  m_userVariablesUsed = !shouldReplaceFunctionsButNotSymbols;
  assert(m_variables[0][0] != 0 && m_variables[1][0] == 0);
  assert(m_type == Type::Monovariable);
  m_numberOfSolutions = 0;
  double start = m_intervalApproximateSolutions[0];
  double step = (m_intervalApproximateSolutions[1]-m_intervalApproximateSolutions[0])*k_precision;
  for (int i = 0; i < k_maxNumberOfApproximateSolutions; i++) {
-    m_approximateSolutions[i] = PoincareHelpers::NextRoot(modelForRecord(definedRecordAtIndex(0))->standardForm(context, shouldReplaceFuncionsButNotSymbols), m_variables[0], start, step, m_intervalApproximateSolutions[1], context);
+    m_approximateSolutions[i] = PoincareHelpers::NextRoot(modelForRecord(definedRecordAtIndex(0))->standardForm(context, shouldReplaceFunctionsButNotSymbols), m_variables[0], start, step, m_intervalApproximateSolutions[1], context);
    if (std::isnan(m_approximateSolutions[i])) {
      break;
    } else {
@@ -120,6 +122,8 @@ void EquationStore::approximateSolve(Poincare::Context * context, bool shouldRep
 EquationStore::Error EquationStore::exactSolve(Poincare::Context * context, bool replaceFunctionsButNotSymbols) {
  tidySolution();

+  m_userVariablesUsed = !replaceFunctionsButNotSymbols;
+
  // Step 0. Get unknown variables
  m_variables[0][0] = 0;
  int numberOfVariables = 0;
@@ -131,7 +135,7 @@ EquationStore::Error EquationStore::exactSolve(Poincare::Context * context, bool
    if (e.type() == ExpressionNode::Type::Unreal) {
      return Error::EquationUnreal;
    }
-    numberOfVariables = e.getVariables(context, [](const char * symbol) { return true; }, (char *)m_variables, Poincare::SymbolAbstract::k_maxNameSize);
+    numberOfVariables = e.getVariables(context, [](const char * symbol, Poincare::Context * context) { return true; }, (char *)m_variables, Poincare::SymbolAbstract::k_maxNameSize);
    if (numberOfVariables == -1) {
      return Error::TooManyVariables;
    }
@@ -140,7 +144,22 @@ EquationStore::Error EquationStore::exactSolve(Poincare::Context * context, bool
    assert(numberOfVariables >= 0);
  }

-  // Step 1. Linear System?
+  // Step 1. Get user defined variables
+  // TODO used previously fetched variables?
+  m_userVariables[0][0] = 0;
+  m_numberOfUserVariables = 0;
+  for (int i = 0; i < numberOfDefinedModels(); i++) {
+    const Expression e = modelForRecord(definedRecordAtIndex(i))->standardForm(context, true);
+    assert(!e.isUninitialized() && e.type() != ExpressionNode::Type::Undefined && e.type() != ExpressionNode::Type::Unreal);
+    int varCount = e.getVariables(context, [](const char * symbol, Poincare::Context * context) { return context->expressionTypeForIdentifier(symbol, strlen(symbol)) == Poincare::Context::SymbolAbstractType::Symbol; }, (char *)m_userVariables, Poincare::SymbolAbstract::k_maxNameSize);
+    if (varCount < 0) {
+      m_numberOfUserVariables = Expression::k_maxNumberOfVariables;
+      break;
+    }
+    m_numberOfUserVariables = varCount;
+  }
+
+  // Step 2. Linear System?

  /* Create matrix coefficients and vector constants as:
   *   coefficients * (x y z ...) = constants */
@@ -177,7 +196,7 @@ EquationStore::Error EquationStore::exactSolve(Poincare::Context * context, bool
    m_type = Type::LinearSystem;
    error = resolveLinearSystem(exactSolutions, exactSolutionsApproximations, coefficients, constants, context);
  } else {
-    // Step 2. Polynomial & Monovariable?
+    // Step 3. Polynomial & Monovariable?
    assert(numberOfVariables == 1 && numberOfDefinedModels() == 1);
    Expression polynomialCoefficients[Expression::k_maxNumberOfPolynomialCoefficients];
    int degree = modelForRecord(definedRecordAtIndex(0))->standardForm(context, replaceFunctionsButNotSymbols).getPolynomialReducedCoefficients(m_variables[0], polynomialCoefficients, context, updatedComplexFormat(context), preferences->angleUnit());
@@ -186,7 +205,7 @@ EquationStore::Error EquationStore::exactSolve(Poincare::Context * context, bool
      m_type = Type::PolynomialMonovariable;
      error = oneDimensialPolynomialSolve(exactSolutions, exactSolutionsApproximations, polynomialCoefficients, degree, context);
    } else {
-      // Step 3. Monovariable non-polynomial or polynomial with degree > 2
+      // Step 4. Monovariable non-polynomial or polynomial with degree > 2
      m_type = Type::Monovariable;
      m_intervalApproximateSolutions[0] = -10;
      m_intervalApproximateSolutions[1] = 10;
--- a/apps/solver/equation_store.h
+++ b/apps/solver/equation_store.h
@@ -38,6 +38,16 @@ public:
    assert(i < Poincare::Expression::k_maxNumberOfVariables && m_variables[i][0] != 0);
    return m_variables[i];
  }
+  const char * userVariableAtIndex(size_t i) {
+    assert(i < Poincare::Expression::k_maxNumberOfVariables && m_userVariables[i][0] != 0);
+    return m_userVariables[i];
+  }
+  int numberOfUserVariables() const {
+    return m_numberOfUserVariables;
+  }
+  bool userVariablesUsed() const {
+    return m_userVariablesUsed;
+  }
  int numberOfSolutions() const {
    return m_numberOfSolutions;
  }
@@ -93,6 +103,7 @@ private:
  mutable Equation m_equations[k_maxNumberOfEquations];
  Type m_type;
  char m_variables[Poincare::Expression::k_maxNumberOfVariables][Poincare::SymbolAbstract::k_maxNameSize];
+  char m_userVariables[Poincare::Expression::k_maxNumberOfVariables][Poincare::SymbolAbstract::k_maxNameSize];
  int m_numberOfSolutions;
  Poincare::Layout m_exactSolutionExactLayouts[k_maxNumberOfApproximateSolutions];
  Poincare::Layout m_exactSolutionApproximateLayouts[k_maxNumberOfExactSolutions];
@@ -100,6 +111,8 @@ private:
  bool m_exactSolutionEquality[k_maxNumberOfExactSolutions];
  double m_intervalApproximateSolutions[2];
  double m_approximateSolutions[k_maxNumberOfApproximateSolutions];
+  int m_numberOfUserVariables;
+  bool m_userVariablesUsed;
 };

 }
--- a/apps/solver/solutions_controller.cpp
+++ b/apps/solver/solutions_controller.cpp
@@ -8,6 +8,7 @@
 #include <poincare/horizontal_layout.h>
 #include <poincare/preferences.h>
 #include <poincare/symbol_abstract.h>
+#include <poincare/symbol.h>
 #include <poincare/vertical_offset_layout.h>

 using namespace Poincare;
@@ -17,19 +18,21 @@ namespace Solver {

 static inline KDCoordinate maxCoordinate(KDCoordinate x, KDCoordinate y) { return x > y ? x : y; }

+constexpr KDColor SolutionsController::ContentView::k_backgroundColor;
+
 SolutionsController::ContentView::ContentView(SolutionsController * controller) :
-  m_warningMessageView0(KDFont::SmallFont, I18n::Message::Default, 0.5f, 0.5f, KDColorBlack, Palette::WallScreenDark),
-  m_warningMessageView1(KDFont::SmallFont, I18n::Message::Default, 0.5f, 0.5f, KDColorBlack, Palette::WallScreenDark),
+  m_warningMessageView0(KDFont::SmallFont, I18n::Message::Default, 0.5f, 0.5f, KDColorBlack, k_backgroundColor),
+  m_warningMessageView1(KDFont::SmallFont, I18n::Message::Default, 0.5f, 0.5f, KDColorBlack, k_backgroundColor),
  m_selectableTableView(controller),
  m_displayWarningMoreSolutions(false)
 {
-  m_selectableTableView.setBackgroundColor(Palette::WallScreenDark);
+  m_selectableTableView.setBackgroundColor(k_backgroundColor);
  m_selectableTableView.setVerticalCellOverlap(0);
 }

 void SolutionsController::ContentView::drawRect(KDContext * ctx, KDRect rect) const {
  if (m_displayWarningMoreSolutions) {
-    ctx->fillRect(KDRect(0, 0, bounds().width(), k_topMargin), Palette::WallScreenDark);
+    ctx->fillRect(KDRect(0, 0, bounds().width(), k_topMargin), k_backgroundColor);
  }
 }

@@ -80,7 +83,7 @@ SolutionsController::SolutionsController(Responder * parentResponder, EquationSt
  m_deltaCell(0.5f, 0.5f),
  m_delta2Layout(),
  m_contentView(this),
-  m_shouldReplaceFuncionsButNotSymbols(false)
+  m_shouldReplaceFunctionsButNotSymbols(false)
 {
  m_delta2Layout = HorizontalLayout::Builder(VerticalOffsetLayout::Builder(CodePointLayout::Builder('2', KDFont::SmallFont), VerticalOffsetLayoutNode::Position::Superscript), LayoutHelper::String("-4ac", 4, KDFont::SmallFont));
  const char * deltaB = "Δ=b";
@@ -93,6 +96,7 @@ SolutionsController::SolutionsController(Responder * parentResponder, EquationSt
  }
  for (int i = 0; i < k_numberOfSymbolCells; i++) {
    m_symbolCells[i].setAlignment(0.5f, 0.5f);
+    m_symbolCells[i].setFont(KDFont::LargeFont);
  }
 }

@@ -109,7 +113,7 @@ void SolutionsController::viewWillAppear() {
  bool requireWarning = false;
  if (m_equationStore->type() == EquationStore::Type::Monovariable) {
    m_contentView.setWarningMessages(I18n::Message::OnlyFirstSolutionsDisplayed0, I18n::Message::OnlyFirstSolutionsDisplayed1);
-    requireWarning = m_equationStore->haveMoreApproximationSolutions(App::app()->localContext(), m_shouldReplaceFuncionsButNotSymbols);
+    requireWarning = m_equationStore->haveMoreApproximationSolutions(App::app()->localContext(), m_shouldReplaceFunctionsButNotSymbols);
  } else if (m_equationStore->type() == EquationStore::Type::PolynomialMonovariable && m_equationStore->numberOfSolutions() == 1) {
    assert(Preferences::sharedPreferences()->complexFormat() == Preferences::ComplexFormat::Real);
    m_contentView.setWarningMessages(I18n::Message::PolynomeHasNoRealSolution0, I18n::Message::PolynomeHasNoRealSolution1);
@@ -158,52 +162,76 @@ Responder * SolutionsController::defaultController() {
 /* TableViewDataSource */

 int SolutionsController::numberOfRows() const {
-  return m_equationStore->numberOfSolutions();
+  return m_equationStore->numberOfSolutions() + (m_equationStore->numberOfUserVariables() > 0 ? 1 + m_equationStore->numberOfUserVariables() : 0);
 }

 void SolutionsController::willDisplayCellAtLocation(HighlightCell * cell, int i, int j) {
+  const int rowOfUserVariablesMessage = userVariablesMessageRow();
+  if (j == rowOfUserVariablesMessage) {
+    // Predefined varaible used/ignored message
+    assert(i >= 0);
+    MessageCell * messageCell = static_cast<MessageCell *>(cell);
+    messageCell->setHorizontalAlignment(i == 0 ? 1.0f : 0.0f);
+    if (usedUserVariables()) {
+      messageCell->setMessage(i == 0 ? I18n::Message::PredefinedVariablesUsedLeft : I18n::Message::PredefinedVariablesUsedRight);
+    } else {
+      messageCell->setMessage(i == 0 ? I18n::Message::PredefinedVariablesIgnoredLeft : I18n::Message::PredefinedVariablesIgnoredRight);
+    }
+    return;
+  }
  if (i == 0) {
-    // Name of the variable or discriminant
    if (m_equationStore->type() == EquationStore::Type::PolynomialMonovariable && j == m_equationStore->numberOfSolutions()-1) {
-      // Discriminant
+      // Formula of the discriminant
      EvenOddExpressionCell * deltaCell = static_cast<EvenOddExpressionCell *>(cell);
      deltaCell->setLayout(m_delta2Layout);
    } else {
      EvenOddBufferTextCell * symbolCell = static_cast<EvenOddBufferTextCell *>(cell);
-      symbolCell->setFont(KDFont::LargeFont);
-      char bufferSymbol[Poincare::SymbolAbstract::k_maxNameSize+1]; // Hold at maximum Delta = b^2-4ac or the variable name + a digit
-      switch (m_equationStore->type()) {
-        case EquationStore::Type::LinearSystem:
+      char bufferSymbol[Poincare::SymbolAbstract::k_maxNameSize+1]; // Holds at maximum the variable name + a digit
+      if (rowOfUserVariablesMessage < 0 || j < rowOfUserVariablesMessage) {
+        // Solution symbol name
+        if (m_equationStore->type() == EquationStore::Type::LinearSystem) {
          /* The system has more than one variable: the cell text is the
           * variable name */
          strlcpy(bufferSymbol, m_equationStore->variableAtIndex(j), Poincare::SymbolAbstract::k_maxNameSize);
-          break;
-        default:
+        } else {
          /* The system has one variable but might have many solutions: the cell
           * text is variableX, with X the row index + 1 (e.g. x1, x2,...) */
          int length = strlcpy(bufferSymbol, m_equationStore->variableAtIndex(0), Poincare::SymbolAbstract::k_maxNameSize);
-          bufferSymbol[length++] = j+'1';
+          bufferSymbol[length++] = j+'1'; // TODO LEA change for 10
          bufferSymbol[length] = 0;
-          break;
+        }
+      } else {
+        // User variable name
+        assert(rowOfUserVariablesMessage > 0);
+        strlcpy(bufferSymbol, m_equationStore->userVariableAtIndex(j - rowOfUserVariablesMessage - 1), Poincare::SymbolAbstract::k_maxNameSize);
      }
      symbolCell->setText(bufferSymbol);
    }
  } else {
-    // Value of the variable or discriminant
-    if (m_equationStore->type() == EquationStore::Type::Monovariable) {
-      EvenOddBufferTextCell * valueCell = static_cast<EvenOddBufferTextCell *>(cell);
-      constexpr int precision = Preferences::LargeNumberOfSignificantDigits;
-      constexpr int bufferSize = PrintFloat::charSizeForFloatsWithPrecision(precision);
-      char bufferValue[bufferSize];
-      PoincareHelpers::ConvertFloatToText<double>(m_equationStore->approximateSolutionAtIndex(j), bufferValue, bufferSize, precision);
-      valueCell->setText(bufferValue);
-    } else {
-      ScrollableTwoExpressionsCell * valueCell = static_cast<ScrollableTwoExpressionsCell *>(cell);
-      Poincare::Layout exactLayout = m_equationStore->exactSolutionLayoutsAtIndexAreIdentical(j) ? Poincare::Layout() : m_equationStore->exactSolutionLayoutAtIndex(j, true);
-      valueCell->setLayouts(exactLayout, m_equationStore->exactSolutionLayoutAtIndex(j, false));
-      if (!exactLayout.isUninitialized()) {
-        valueCell->setEqualMessage(m_equationStore->exactSolutionLayoutsAtIndexAreEqual(j) ? I18n::Message::Equal : I18n::Message::AlmostEqual);
+    if (rowOfUserVariablesMessage < 0 || j < rowOfUserVariablesMessage) {
+      if (m_equationStore->type() == EquationStore::Type::Monovariable) {
+        // Values of the solutions
+        EvenOddBufferTextCell * valueCell = static_cast<EvenOddBufferTextCell *>(cell);
+        constexpr int precision = Preferences::LargeNumberOfSignificantDigits;
+        constexpr int bufferSize = PrintFloat::charSizeForFloatsWithPrecision(precision);
+        char bufferValue[bufferSize];
+        PoincareHelpers::ConvertFloatToText<double>(m_equationStore->approximateSolutionAtIndex(j), bufferValue, bufferSize, precision);
+        valueCell->setText(bufferValue);
+      } else {
+        // Values of the solutions or discriminant
+        ScrollableTwoExpressionsCell * valueCell = static_cast<ScrollableTwoExpressionsCell *>(cell);
+        Poincare::Layout exactLayout = m_equationStore->exactSolutionLayoutsAtIndexAreIdentical(j) ? Poincare::Layout() : m_equationStore->exactSolutionLayoutAtIndex(j, true);
+        valueCell->setLayouts(exactLayout, m_equationStore->exactSolutionLayoutAtIndex(j, false));
+        if (!exactLayout.isUninitialized()) {
+          valueCell->setEqualMessage(m_equationStore->exactSolutionLayoutsAtIndexAreEqual(j) ? I18n::Message::Equal : I18n::Message::AlmostEqual);
+        }
      }
+    } else {
+      // Values of the solutions or discriminant
+      ScrollableTwoExpressionsCell * valueCell = static_cast<ScrollableTwoExpressionsCell *>(cell);
+      const char * symbol = m_equationStore->userVariableAtIndex(j - rowOfUserVariablesMessage - 1);
+      Poincare::Layout layout = PoincareHelpers::CreateLayout(App::app()->localContext()->expressionForSymbolAbstract(Poincare::Symbol::Builder(symbol, strlen(symbol)), false));
+      valueCell->setLayouts(Poincare::Layout(), layout);
    }
  }
  EvenOddCell * evenOddCell = static_cast<EvenOddCell *>(cell);
@@ -218,12 +246,22 @@ KDCoordinate SolutionsController::rowHeight(int j) {
  if (m_equationStore->type() == EquationStore::Type::Monovariable) {
    return k_defaultCellHeight;
  }
-  Poincare::Layout exactLayout = m_equationStore->exactSolutionLayoutAtIndex(j, true);
-  Poincare::Layout approximateLayout = m_equationStore->exactSolutionLayoutAtIndex(j, false);
-  KDCoordinate exactLayoutHeight = exactLayout.layoutSize().height();
-  KDCoordinate approximateLayoutHeight = approximateLayout.layoutSize().height();
-  KDCoordinate layoutHeight = maxCoordinate(exactLayout.baseline(), approximateLayout.baseline()) + maxCoordinate(exactLayoutHeight-exactLayout.baseline(), approximateLayoutHeight-approximateLayout.baseline());
-  return layoutHeight + 2 * Metric::CommonSmallMargin;
+  const int rowOfUserVariablesMessage = userVariablesMessageRow();
+  if (rowOfUserVariablesMessage < 0 || j < rowOfUserVariablesMessage) {
+    Poincare::Layout exactLayout = m_equationStore->exactSolutionLayoutAtIndex(j, true);
+    Poincare::Layout approximateLayout = m_equationStore->exactSolutionLayoutAtIndex(j, false);
+    KDCoordinate exactLayoutHeight = exactLayout.layoutSize().height();
+    KDCoordinate approximateLayoutHeight = approximateLayout.layoutSize().height();
+    KDCoordinate layoutHeight = maxCoordinate(exactLayout.baseline(), approximateLayout.baseline()) + maxCoordinate(exactLayoutHeight-exactLayout.baseline(), approximateLayoutHeight-approximateLayout.baseline());
+    return layoutHeight + 2 * Metric::CommonSmallMargin;
+  }
+  if (j == rowOfUserVariablesMessage) {
+    return Metric::CommonTopMargin + k_defaultCellHeight + Metric::CommonBottomMargin;
+  }
+  // TODO: memoize user symbols if too slow
+  const char * symbol = m_equationStore->userVariableAtIndex(j - rowOfUserVariablesMessage - 1);
+  Poincare::Layout layout = PoincareHelpers::CreateLayout(App::app()->localContext()->expressionForSymbolAbstract(Poincare::Symbol::Builder(symbol, strlen(symbol)), false));
+  return layout.layoutSize().height() + 2 * Metric::CommonSmallMargin;
 }

 KDCoordinate SolutionsController::cumulatedWidthFromIndex(int i) {
@@ -232,11 +270,9 @@ KDCoordinate SolutionsController::cumulatedWidthFromIndex(int i) {
      return 0;
    case 1:
      return k_symbolCellWidth;
-    case 2:
-      return k_symbolCellWidth+k_valueCellWidth;
    default:
-      assert(false);
-      return 0;
+      assert(i == 2);
+      return k_symbolCellWidth+k_valueCellWidth;
  }
 }

@@ -260,6 +296,8 @@ HighlightCell * SolutionsController::reusableCell(int index, int type) {
      return &m_deltaCell;
    case k_exactValueCellType:
      return &m_exactValueCells[index];
+    case k_messageCellType:
+      return &m_messageCells[index];
    default:
      assert(type == k_approximateValueCellType);
      return &m_approximateValueCells[index];
@@ -269,29 +307,43 @@ HighlightCell * SolutionsController::reusableCell(int index, int type) {
 int SolutionsController::reusableCellCount(int type) {
  switch (type) {
    case k_symbolCellType:
-      return EquationStore::k_maxNumberOfSolutions;
+      return k_numberOfSymbolCells;
    case k_deltaCellType:
      return 1;
    case k_exactValueCellType:
-      return EquationStore::k_maxNumberOfExactSolutions;
+      return k_numberOfExactValueCells;
+    case k_messageCellType:
+      return k_numberOfMessageCells;
    default:
      assert(type == k_approximateValueCellType);
-      return EquationStore::k_maxNumberOfApproximateSolutions;
+      return k_numberOfApproximateValueCells;
  }
 }

 int SolutionsController::typeAtLocation(int i, int j) {
+  const int rowOfUserVariableMessage = userVariablesMessageRow();
+  if (j == rowOfUserVariableMessage) {
+    return k_messageCellType;
+  }
  if (i == 0) {
    if (m_equationStore->type() == EquationStore::Type::PolynomialMonovariable && j == m_equationStore->numberOfSolutions()-1) {
      return k_deltaCellType;
    }
    return k_symbolCellType;
  }
-  return m_equationStore->type() == EquationStore::Type::Monovariable ? k_approximateValueCellType : k_exactValueCellType;
+  if ((rowOfUserVariableMessage < 0 || j < rowOfUserVariableMessage) && m_equationStore->type() == EquationStore::Type::Monovariable) {
+    return k_approximateValueCellType;
+  }
+  return k_exactValueCellType;
 }

 void SolutionsController::didBecomeFirstResponder() {
  Container::activeApp()->setFirstResponder(m_contentView.selectableTableView());
 }

+int SolutionsController::userVariablesMessageRow() const {
+  assert(m_equationStore->numberOfUserVariables() >= 0);
+  return m_equationStore->numberOfUserVariables() == 0 ? -1 : m_equationStore->numberOfSolutions();
+}
+
 }
--- a/apps/solver/solutions_controller.h
+++ b/apps/solver/solutions_controller.h
@@ -11,8 +11,8 @@ namespace Solver {
 class SolutionsController : public ViewController, public AlternateEmptyViewDefaultDelegate, public SelectableTableViewDataSource, public TableViewDataSource {
 public:
  SolutionsController(Responder * parentResponder, EquationStore * equationStore);
-  void setShouldReplaceFuncionsButNotSymbols(bool shouldReplaceFuncionsButNotSymbols) { m_shouldReplaceFuncionsButNotSymbols = shouldReplaceFuncionsButNotSymbols; }
-  bool shouldReplaceFuncionsButNotSymbols() const { return m_shouldReplaceFuncionsButNotSymbols; }
+  void setShouldReplaceFuncionsButNotSymbols(bool shouldReplaceFuncionsButNotSymbols) { m_shouldReplaceFunctionsButNotSymbols = shouldReplaceFuncionsButNotSymbols; }
+  bool shouldReplaceFuncionsButNotSymbols() const { return m_shouldReplaceFunctionsButNotSymbols; }
  /* ViewController */
  const char * title() override;
  View * view() override { return &m_contentView; }
@@ -40,13 +40,12 @@ private:
  class ContentView : public View {
  public:
    constexpr static KDCoordinate k_topMargin = 50;
+    constexpr static KDColor k_backgroundColor = Palette::WallScreenDark;
    ContentView(SolutionsController * controller);
    void drawRect(KDContext * ctx, KDRect rect) const override;
    void setWarning(bool warning);
    void setWarningMessages(I18n::Message message0, I18n::Message message1);
-    SelectableTableView * selectableTableView() {
-      return &m_selectableTableView;
-    }
+    SelectableTableView * selectableTableView() { return &m_selectableTableView; }
  private:
    constexpr static KDCoordinate k_middleMargin = 50;
    int numberOfSubviews() const override;
@@ -58,11 +57,26 @@ private:
    bool m_displayWarningMoreSolutions;
  };

+  class MessageCell : public HighlightCell {
+  public:
+    MessageCell() : m_messageView(KDFont::SmallFont, (I18n::Message)0, 0.0f, k_verticalAlignment, KDColorBlack, SolutionsController::ContentView::k_backgroundColor) {}
+    void setBackgroundColor(KDColor color) { m_messageView.setBackgroundColor(color); }
+    void setHorizontalAlignment(float alignment) { m_messageView.setAlignment(alignment, k_verticalAlignment); }
+    void setMessage(I18n::Message message) { m_messageView.setMessage(message); }
+  private:
+    constexpr static float k_verticalAlignment = 0.8f;
+    int numberOfSubviews() const override { return 1; }
+    View * subviewAtIndex(int index) override { assert(index == 0); return &m_messageView; }
+    void layoutSubviews(bool force = false) override { m_messageView.setFrame(bounds(), force); }
+    MessageTextView m_messageView;
+  };
+
  // Cell types
  constexpr static int k_symbolCellType = 0;
  constexpr static int k_deltaCellType = 1;
  constexpr static int k_exactValueCellType = 2;
  constexpr static int k_approximateValueCellType = 3;
+  constexpr static int k_messageCellType = 4;

  // Heights and widths
  constexpr static KDCoordinate k_defaultCellHeight = 20;
@@ -70,11 +84,19 @@ private:
  constexpr static int k_valueCellWidth = 190;

  // Number of cells
-  constexpr static int k_maxNumberOfVisibleCells = (Ion::Display::Height - 3 * Meric::TitleBarHeight - ContentView::k_topMargin) / k_defaultCellHeight + 1;
+  constexpr static int k_maxNumberOfVisibleCells = (Ion::Display::Height - 3 * Metric::TitleBarHeight - ContentView::k_topMargin) / k_defaultCellHeight + 1;
  static_assert(k_maxNumberOfVisibleCells <= EquationStore::k_maxNumberOfSolutions + Poincare::Expression::k_maxNumberOfVariables, "We can reduce the number of cells in Solver:SolutionsController.");
-  constexpr static int k_numberOfSymbolCells = k_maxNumberOfVisibleCells < EquationStore::k_maxNumberOfSolutions ? k_maxNumberOfVisibleCells : EquationStore::k_maxNumberOfSolutions;
-  constexpr static int k_numberOfExactValueCells = k_maxNumberOfVisibleCells < EquationStore::k_maxNumberOfExactSolutions ? k_maxNumberOfVisibleCells : EquationStore::k_maxNumberOfExactSolutions;
+  constexpr static int k_maxNumberOfSymbols = EquationStore::k_maxNumberOfSolutions + Poincare::Expression::k_maxNumberOfVariables;
+  constexpr static int k_numberOfSymbolCells = k_maxNumberOfVisibleCells < k_maxNumberOfSymbols ? k_maxNumberOfVisibleCells : k_maxNumberOfSymbols;
+  constexpr static int k_maxNumberOfExactValues = EquationStore::k_maxNumberOfExactSolutions + Poincare::Expression::k_maxNumberOfVariables;
+  constexpr static int k_numberOfExactValueCells = k_maxNumberOfVisibleCells < k_maxNumberOfExactValues ? k_maxNumberOfVisibleCells : k_maxNumberOfExactValues;
  constexpr static int k_numberOfApproximateValueCells = k_maxNumberOfVisibleCells < EquationStore::k_maxNumberOfApproximateSolutions ? k_maxNumberOfVisibleCells : EquationStore::k_maxNumberOfApproximateSolutions;
+  constexpr static int k_numberOfMessageCells = 2;
+
+  bool usedUserVariables() const {
+    return m_equationStore->userVariablesUsed();
+  }
+  int userVariablesMessageRow() const;

  EquationStore * m_equationStore;
  EvenOddBufferTextCell m_symbolCells[k_numberOfSymbolCells];
@@ -82,8 +104,9 @@ private:
  Poincare::Layout m_delta2Layout;
  Shared::ScrollableTwoExpressionsCell m_exactValueCells[k_numberOfExactValueCells];
  EvenOddBufferTextCell m_approximateValueCells[k_numberOfApproximateValueCells];
+  MessageCell m_messageCells[k_numberOfMessageCells];
  ContentView m_contentView;
-  bool m_shouldReplaceFuncionsButNotSymbols;
+  bool m_shouldReplaceFunctionsButNotSymbols;
 };

 }