diff --git a/poincare/Makefile b/poincare/Makefile
index 01daab901..cb32f93a3 100644
--- a/poincare/Makefile
+++ b/poincare/Makefile
@@ -28,8 +28,9 @@ objs += $(addprefix poincare/src/layout/,\
   string_layout.o\
 )
 objs += $(addprefix poincare/src/simplify/,\
-  expression_selector.o\
   expression_builder.o\
+  expression_match.o\
+  expression_selector.o\
   simplification.o\
 	simplification_generator.o\
 	simplification_rules.o\
diff --git a/poincare/include/poincare/addition.h b/poincare/include/poincare/addition.h
index 591c020b3..e5a1b7ffc 100644
--- a/poincare/include/poincare/addition.h
+++ b/poincare/include/poincare/addition.h
@@ -9,6 +9,9 @@ class Addition : public CommutativeOperation {
     Type type() override;
     float operateApproximatevelyOn(float a, float b) override;
     Expression * clone() override;
+#ifdef DEBUG
+    int getPrintableVersion(char* txt) override;
+#endif
   protected:
     char operatorChar() override;
 };
diff --git a/poincare/include/poincare/cosine.h b/poincare/include/poincare/cosine.h
index 31f376375..af0aa391f 100644
--- a/poincare/include/poincare/cosine.h
+++ b/poincare/include/poincare/cosine.h
@@ -9,6 +9,9 @@ class Cosine : public Function {
     float approximate(Context& context) override;
     Type type() override;
     Expression * clone() override;
+#ifdef DEBUG
+    int getPrintableVersion(char* txt) override;
+#endif
 };
 
 #endif
diff --git a/poincare/include/poincare/expression.h b/poincare/include/poincare/expression.h
index d44539469..617787de8 100644
--- a/poincare/include/poincare/expression.h
+++ b/poincare/include/poincare/expression.h
@@ -4,6 +4,12 @@
 #include <poincare/expression_layout.h>
 #include <kandinsky.h>
 
+#ifdef DEBUG
+#define PRINT_AST(e)  e->__printAst(0)
+#else
+#define PRINT_AST(e) ((void)0)
+#endif
+
 class Context;
 
 class Expression {
@@ -12,8 +18,8 @@ class Expression {
       Addition,
       Cosine,
       Float,
-      Fraction,
       Integer,
+      Fraction,
       Power,
       Product,
       Sine,
@@ -45,6 +51,10 @@ class Expression {
   /*private:
     void forEachChild(ExpressionAction);
     */
+#ifdef DEBUG
+    virtual int getPrintableVersion(char* txt) = 0;
+    void __printAst(int level=0);
+#endif
 };
 
 #endif
diff --git a/poincare/include/poincare/float.h b/poincare/include/poincare/float.h
index 245a1e8d9..577b6489f 100644
--- a/poincare/include/poincare/float.h
+++ b/poincare/include/poincare/float.h
@@ -13,6 +13,9 @@ class Float : public LeafExpression {
     Type type() override;
     Expression * clone() override;
     bool valueEquals(Expression * e) override;
+#ifdef DEBUG
+    int getPrintableVersion(char* txt) override;
+#endif
   private:
     float m_float;
 };
diff --git a/poincare/include/poincare/fraction.h b/poincare/include/poincare/fraction.h
index 23fbe9352..fc30c2537 100644
--- a/poincare/include/poincare/fraction.h
+++ b/poincare/include/poincare/fraction.h
@@ -10,6 +10,9 @@ class Fraction : public BinaryOperation {
     float approximate(Context& context) override;
     Type type() override;
     Expression * clone() override;
+#ifdef DEBUG
+    int getPrintableVersion(char* txt) override;
+#endif
 };
 
 #endif
diff --git a/poincare/include/poincare/integer.h b/poincare/include/poincare/integer.h
index b29b2f7b0..aa047ce6c 100644
--- a/poincare/include/poincare/integer.h
+++ b/poincare/include/poincare/integer.h
@@ -45,6 +45,10 @@ class Integer : public LeafExpression {
     native_uint_t * m_digits; // LITTLE-ENDIAN
     uint16_t m_numberOfDigits; // In base native_uint_max
     bool m_negative;
+
+#ifdef DEBUG
+    int getPrintableVersion(char* txt) override;
+#endif
     /*
      // TODO: Small-int optimization
     union {
diff --git a/poincare/include/poincare/power.h b/poincare/include/poincare/power.h
index 4f567a1df..2ee17d5b4 100644
--- a/poincare/include/poincare/power.h
+++ b/poincare/include/poincare/power.h
@@ -10,6 +10,9 @@ class Power : public BinaryOperation {
     float approximate(Context& context) override;
     Type type() override;
     Expression * clone() override;
+#ifdef DEBUG
+    int getPrintableVersion(char* txt) override;
+#endif
 };
 
 #endif
diff --git a/poincare/include/poincare/product.h b/poincare/include/poincare/product.h
index 4b4b50be1..d90fea7a9 100644
--- a/poincare/include/poincare/product.h
+++ b/poincare/include/poincare/product.h
@@ -9,6 +9,9 @@ class Product : public CommutativeOperation {
     Type type() override;
     float operateApproximatevelyOn(float a, float b) override;
     Expression * clone() override;
+#ifdef DEBUG
+    int getPrintableVersion(char* txt) override;
+#endif
   protected:
     char operatorChar() override;
 };
diff --git a/poincare/include/poincare/sine.h b/poincare/include/poincare/sine.h
index fe53563a0..a42024652 100644
--- a/poincare/include/poincare/sine.h
+++ b/poincare/include/poincare/sine.h
@@ -9,6 +9,9 @@ class Sine : public Function {
     float approximate(Context& context) override;
     Type type() override;
     Expression * clone() override;
+#ifdef DEBUG
+    int getPrintableVersion(char* txt) override;
+#endif
 };
 
 #endif
diff --git a/poincare/include/poincare/subtraction.h b/poincare/include/poincare/subtraction.h
index 5054bf390..11eb4b130 100644
--- a/poincare/include/poincare/subtraction.h
+++ b/poincare/include/poincare/subtraction.h
@@ -10,6 +10,9 @@ class Subtraction : public BinaryOperation {
     float approximate(Context& context) override;
     Type type() override;
     Expression * clone() override;
+#ifdef DEBUG
+    int getPrintableVersion(char* txt) override;
+#endif
 };
 
 #endif
diff --git a/poincare/include/poincare/symbol.h b/poincare/include/poincare/symbol.h
index b0e1ebaba..e8b9beb04 100644
--- a/poincare/include/poincare/symbol.h
+++ b/poincare/include/poincare/symbol.h
@@ -12,6 +12,9 @@ class Symbol : public LeafExpression {
     Type type() override;
     Expression * clone() override;
     bool valueEquals(Expression * e) override;
+#ifdef DEBUG
+    int getPrintableVersion(char* txt) override;
+#endif
   private:
     char * m_name;
 };
diff --git a/poincare/include/poincare/tangent.h b/poincare/include/poincare/tangent.h
index 06ffbae06..58ac4bbf2 100644
--- a/poincare/include/poincare/tangent.h
+++ b/poincare/include/poincare/tangent.h
@@ -9,6 +9,9 @@ class Tangent : public Function {
     float approximate(Context& context) override;
     Type type() override;
     Expression * clone() override;
+#ifdef DEBUG
+    int getPrintableVersion(char* txt) override;
+#endif
 };
 
 #endif
diff --git a/poincare/src/addition.cpp b/poincare/src/addition.cpp
index 0783002dc..6108bc061 100644
--- a/poincare/src/addition.cpp
+++ b/poincare/src/addition.cpp
@@ -16,3 +16,10 @@ float Addition::operateApproximatevelyOn(float a, float b) {
 char Addition::operatorChar() {
   return '+';
 }
+
+#ifdef DEBUG
+int Addition::getPrintableVersion(char* txt) {
+  txt[0] = '+';
+  return 1;
+}
+#endif
diff --git a/poincare/src/cosine.cpp b/poincare/src/cosine.cpp
index 8fafad923..a665ca137 100644
--- a/poincare/src/cosine.cpp
+++ b/poincare/src/cosine.cpp
@@ -13,3 +13,13 @@ float Cosine::approximate(Context& context) {
   // FIXME: use cosine obviously.
   return m_arg->approximate(context);
 }
+
+#ifdef DEBUG
+int Cosine::getPrintableVersion(char* txt) {
+  const char* printable = "cos";
+  for(int i=0; printable[i]!='\0'; i++) {
+    txt[i] = printable[i];
+  }
+  return 3;
+}
+#endif
diff --git a/poincare/src/expression.cpp b/poincare/src/expression.cpp
index cb7f19f94..f3cfd5d4d 100644
--- a/poincare/src/expression.cpp
+++ b/poincare/src/expression.cpp
@@ -7,6 +7,11 @@ extern "C" {
 
 #include "simplify/simplification_rules.h"
 
+#ifdef DEBUG
+#include <iostream>
+using namespace std;
+#endif
+
 int poincare_expression_yyparse(yyscan_t scanner, Expression ** expressionOutput);
 
 Expression::~Expression() {
@@ -33,6 +38,8 @@ Expression * Expression::simplify() {
       const Simplification * simplification = (simplifications + i); // Pointer arithmetics
       Expression * simplified = simplification->simplify(result);
       if (simplified != nullptr) {
+        std::cout << "simplification " << i << " returned a non null pointer" << std::endl;
+        PRINT_AST(simplified);
         simplification_pass_was_useful = true;
         if (result != this) {
           delete result;
@@ -63,3 +70,18 @@ bool Expression::valueEquals(Expression * e) {
    * -riden. */
   return true;
 }
+
+#ifdef DEBUG
+void Expression::__printAst(int level) {
+  char txt[255];
+  for (int i(0); i<level; i++) {
+    txt[i] = ' ';
+  }
+  int offset = getPrintableVersion(&txt[level]);
+  txt[level + offset] = '\0';
+  std::cout << txt << std::endl;
+  for (int i(0); i < numberOfOperands(); i++) {
+    operand(i)->__printAst(level + 2);
+  }
+}
+#endif
diff --git a/poincare/src/float.cpp b/poincare/src/float.cpp
index 88fade139..fb5ce3163 100644
--- a/poincare/src/float.cpp
+++ b/poincare/src/float.cpp
@@ -1,8 +1,11 @@
-#include <poincare/float.h>
+#include <stdlib.h>
+#include <string.h>
 extern "C" {
 #include <assert.h>
 }
 
+#include <poincare/float.h>
+
 Float::Float(float f) : m_float(f) {
 }
 
@@ -30,3 +33,13 @@ bool Float::valueEquals(Expression * e) {
   assert(e->type() == Expression::Type::Float);
   return m_float == ((Float *)e)->m_float;
 }
+
+#ifdef DEBUG
+int Float::getPrintableVersion(char* txt) {
+  const char* printable = "float number";
+  for(int i=0; printable[i]!='\0'; i++) {
+    txt[i] = printable[i];
+  }
+  return strlen(printable);
+}
+#endif
diff --git a/poincare/src/fraction.cpp b/poincare/src/fraction.cpp
index 10893c814..fc66955ed 100644
--- a/poincare/src/fraction.cpp
+++ b/poincare/src/fraction.cpp
@@ -18,3 +18,10 @@ float Fraction::approximate(Context& context) {
 Expression::Type Fraction::type() {
   return Expression::Type::Fraction;
 }
+
+#ifdef DEBUG
+int Fraction::getPrintableVersion(char* txt) {
+  txt[0] = '/';
+  return 1;
+}
+#endif
diff --git a/poincare/src/integer.cpp b/poincare/src/integer.cpp
index 78de87385..e2d3c58fc 100644
--- a/poincare/src/integer.cpp
+++ b/poincare/src/integer.cpp
@@ -344,6 +344,30 @@ ExpressionLayout * Integer::createLayout() {
   return new StringLayout(buffer, size);
 }
 
+#ifdef DEBUG
+int Integer::getPrintableVersion(char* txt) {
+  Integer base = Integer(10);
+  Division d = Division(*this, base);
+  int size = 0;
+  while (!(d.m_remainder == Integer((native_int_t)0))) {
+    assert(size<255); //TODO: malloc an extra buffer
+    char c = char_from_digit(d.m_remainder.m_digits[0]);
+    txt[size++] = c;
+    d = Division(d.m_quotient, base);
+  }
+  txt[size] = 0;
+
+  // Flip the string
+  for (int i=0, j=size-1 ; i < j ; i++, j--) {
+    char c = txt[i];
+    txt[i] = txt[j];
+    txt[j] = c;
+  }
+
+  return size;
+}
+#endif
+
 bool Integer::valueEquals(Expression * e) {
   assert(e->type() == Expression::Type::Integer);
   return (*this == *(Integer *)e); // FIXME: Remove operator overloading
diff --git a/poincare/src/power.cpp b/poincare/src/power.cpp
index 6eb6cb2f4..718cffb5b 100644
--- a/poincare/src/power.cpp
+++ b/poincare/src/power.cpp
@@ -17,3 +17,10 @@ Expression::Type Power::type() {
 ExpressionLayout * Power::createLayout() {
   return new ExponentLayout(m_operands[0]->createLayout(), m_operands[1]->createLayout());
 }
+
+#ifdef DEBUG
+int Power::getPrintableVersion(char* txt) {
+  txt[0] = '^';
+  return 1;
+}
+#endif
diff --git a/poincare/src/print_ast.cpp b/poincare/src/print_ast.cpp
new file mode 100644
index 000000000..6f6470887
--- /dev/null
+++ b/poincare/src/print_ast.cpp
@@ -0,0 +1,19 @@
+#include <poincare/integer.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+int __print_ast(Expression* expression, int offset) {
+  // TODO print my current node.
+  char txt[offset+1] = {' '};
+  text[offset] = '\0';
+  cout << txt;
+
+  // Print my children.
+  for (int i(0); i<expression->m_operands(); i++) {
+    int tmp = __print_ast(expression->operand(i), offset);
+    offset += tmp;
+  }
+
+  return 3;
+}
diff --git a/poincare/src/product.cpp b/poincare/src/product.cpp
index 7fefa4ca1..8c0f5a58b 100644
--- a/poincare/src/product.cpp
+++ b/poincare/src/product.cpp
@@ -19,3 +19,10 @@ Expression::Type Product::type() {
 char Product::operatorChar() {
   return '*';
 }
+
+#ifdef DEBUG
+int Product::getPrintableVersion(char* txt) {
+  txt[0] = '*';
+  return 1;
+}
+#endif
diff --git a/poincare/src/simplify/expression_builder.cpp b/poincare/src/simplify/expression_builder.cpp
index aeeadfc4a..6afe4c707 100644
--- a/poincare/src/simplify/expression_builder.cpp
+++ b/poincare/src/simplify/expression_builder.cpp
@@ -1,34 +1,39 @@
 #include "expression_builder.h"
 #include <poincare/addition.h>
 #include <poincare/integer.h>
+#include <poincare/product.h>
 extern "C" {
 #include <assert.h>
 }
 
-/* Our compiler defines two things:
- * - First, a list of ExpressionBuilder
- * - Second, a children_expression_buffer[] of the proper size.
- */
-
-Expression * children_expression_buffer[4]; // This will be defined by our compiler
-
-Expression * ExpressionBuilder::build(Expression * matches[]) {
+Expression * ExpressionBuilder::build(ExpressionMatch matches[]) {
   Expression * children_expressions[255]; // FIXME: <- The sized can be given by the compiler
   //Expression * children_expressions = malloc;
-// That malloc can be avoided: we can give an upper bound
-// Afer we've finished processing the rules
-// That upper bound is likely to be very small (3, currently)
+  // That malloc can be avoided: we can give an upper bound
+  // Afer we've finished processing the rules
+  // That upper bound is likely to be very small (3, currently)
+  int numberOfChildrenExpressions = 0;
 
   for (int i=0; i<m_numberOfChildren; i++) {
     ExpressionBuilder * child = this->child(i);
-    children_expressions[i] = child->build(matches);
+    if (child->m_action == ExpressionBuilder::Action::BringUpWildcard) {
+      for (int j=0; j<matches[child->m_matchIndex].numberOfExpressions(); j++) {
+        children_expressions[numberOfChildrenExpressions++] =
+          matches[child->m_matchIndex].expression(j)->clone();
+      }
+    } else {
+      children_expressions[numberOfChildrenExpressions++] = child->build(matches);
+    }
   }
   Expression * result = nullptr;
   switch(m_action) {
     case ExpressionBuilder::Action::BuildFromTypeAndValue:
       switch(m_expressionType) {
         case Expression::Type::Addition:
-          result = new Addition(children_expressions, m_numberOfChildren, true);
+          result = new Addition(children_expressions, numberOfChildrenExpressions, true);
+          break;
+        case Expression::Type::Product:
+          result = new Product(children_expressions, numberOfChildrenExpressions, true);
           break;
         case Expression::Type::Integer:
           result = new Integer(m_integerValue);
@@ -38,11 +43,17 @@ Expression * ExpressionBuilder::build(Expression * matches[]) {
           break;
       }
       break;
+    case ExpressionBuilder::Action::BringUpWildcard:
+      // Build should never be called on BringUpWildcard action directly
+      assert(false);
+      break;
     case ExpressionBuilder::Action::Clone:
-      result = matches[m_matchIndex]->clone();
+      // It only makes sense to clone if the match has a single expression!
+      assert(matches[m_matchIndex].numberOfExpressions() == 1);
+      result = matches[m_matchIndex].expression(0)->clone();
       break;
     case ExpressionBuilder::Action::CallExternalGenerator:
-      result = m_generator(children_expressions, m_numberOfChildren);
+      result = m_generator(children_expressions, numberOfChildrenExpressions);
       break;
   }
   return result;
diff --git a/poincare/src/simplify/expression_builder.h b/poincare/src/simplify/expression_builder.h
index 0eb4488ad..77b18ef6e 100644
--- a/poincare/src/simplify/expression_builder.h
+++ b/poincare/src/simplify/expression_builder.h
@@ -2,6 +2,7 @@
 #define POINCARE_SIMPLIFY_EXPRESSION_BUILDER_H
 
 #include <poincare/expression.h>
+#include "expression_match.h"
 extern "C" {
 #include <stdint.h>
 }
@@ -11,11 +12,12 @@ class ExpressionBuilder {
   typedef Expression * (ExternalGenerator)(Expression ** parameters, int numberOfParameters);
 public:
   ExpressionBuilder * child(int i);
-  Expression * build(Expression * matches[]);
+  Expression * build(ExpressionMatch matches[]);
 
   enum class Action {
     BuildFromTypeAndValue,
     Clone,
+    BringUpWildcard,
     CallExternalGenerator
   };
 
@@ -32,7 +34,7 @@ public:
         char const * m_symbolName;
       };
     };
-    // m_action == Clone
+    // m_action == Clone or BringUpWildcard
     uint8_t m_matchIndex;
     // m_action == CallExternalGenerator
     ExternalGenerator * m_generator;
diff --git a/poincare/src/simplify/expression_match.cpp b/poincare/src/simplify/expression_match.cpp
new file mode 100644
index 000000000..5ddcb3a5e
--- /dev/null
+++ b/poincare/src/simplify/expression_match.cpp
@@ -0,0 +1,44 @@
+#include "expression_match.h"
+
+extern "C" {
+#include <assert.h>
+#include <stdlib.h>
+}
+
+#include <iostream>
+using namespace std;
+
+ExpressionMatch::ExpressionMatch() {
+  m_numberOfExpressions = 0;
+  m_expressions = nullptr;
+}
+
+ExpressionMatch::ExpressionMatch(Expression ** expressions, int numberOfExpressions) {
+  m_numberOfExpressions = numberOfExpressions;
+  m_expressions = (Expression**) malloc(m_numberOfExpressions * sizeof(ExpressionMatch*));
+  for (int i(0); i<numberOfExpressions; i++) {
+    m_expressions[i] = expressions[i];
+  }
+}
+
+ExpressionMatch::~ExpressionMatch() {
+  if (m_numberOfExpressions != 0) {
+    free(m_expressions);
+  }
+}
+
+Expression * ExpressionMatch::expression(int i) {
+  assert(i < m_numberOfExpressions);
+  return m_expressions[i];
+}
+
+int ExpressionMatch::numberOfExpressions() {
+  return m_numberOfExpressions;
+}
+
+ExpressionMatch& ExpressionMatch::operator=(ExpressionMatch&& other) {
+  m_numberOfExpressions = other.m_numberOfExpressions;
+  other.m_numberOfExpressions = 0; // Here we make sure that the memory containing the expressions is not freed.
+  m_expressions = other.m_expressions;
+  return *this;
+}
diff --git a/poincare/src/simplify/expression_match.h b/poincare/src/simplify/expression_match.h
new file mode 100644
index 000000000..31e8ae7e4
--- /dev/null
+++ b/poincare/src/simplify/expression_match.h
@@ -0,0 +1,22 @@
+#ifndef POINCARE_SIMPLIFY_EXPRESSION_MATCH_H
+#define POINCARE_SIMPLIFY_EXPRESSION_MATCH_H
+
+#include <poincare/expression.h>
+extern "C" {
+#include <stdint.h>
+}
+
+class ExpressionMatch {
+public:
+  ExpressionMatch();
+  ExpressionMatch(Expression ** expressions, int numberOfExpressions);
+  ~ExpressionMatch();
+  Expression * expression(int i);
+  int numberOfExpressions();
+  ExpressionMatch& operator=(ExpressionMatch&& other);
+private:
+  Expression ** m_expressions;
+  int m_numberOfExpressions;
+};
+
+#endif
diff --git a/poincare/src/simplify/expression_selector.cpp b/poincare/src/simplify/expression_selector.cpp
index 8c7a90df9..edee3d613 100644
--- a/poincare/src/simplify/expression_selector.cpp
+++ b/poincare/src/simplify/expression_selector.cpp
@@ -3,7 +3,7 @@ extern "C" {
 #include <assert.h>
 }
 
-int ExpressionSelector::match(Expression * e, ExpressionMatch ** matches) {
+int ExpressionSelector::match(Expression * e, ExpressionMatch * matches) {
   int numberOfMatches = 0;
 
   // Does the current node match?
@@ -11,7 +11,7 @@ int ExpressionSelector::match(Expression * e, ExpressionMatch ** matches) {
     case ExpressionSelector::Match::Any:
       // Yes, it always does!
       break;
-    case ExpressionSelector::Match::TypeAndValue:
+    case ExpressionSelector::Match::Type:
       if (e->type() != m_expressionType) {
         return 0;
       }
@@ -23,32 +23,26 @@ int ExpressionSelector::match(Expression * e, ExpressionMatch ** matches) {
   }
 
   // The current node does match. Let's add it to our matches
-  // FIXME
   matches[numberOfMatches++] = ExpressionMatch(&e, 1);
-  //matches[numberOfMatches++] = e;
-
-  // FIXME: For now we'll ignore the commutativity of the Selector
-  // which is definitely something *very* important
-  // Checking if "e" is commutative seems like a nice solution
 
   for (int i=0; i<m_numberOfChildren; i++) {
     ExpressionSelector * childSelector = this->child(i);
-    // To account for commutativity, we should have multiple possibilities for childExpression
     Expression * childExpression = e->operand(i);
+
     if (childSelector->m_match == ExpressionSelector::Match::WildCard) {
       assert(i == m_numberOfChildren-1); // Wildcards should be the last argument!
-      Expression * pouet[255];//TODO
-      for (int j=i; j<childSelector->numberOfOperands(); j++) {
-        pouet[j-i] = e->operand(j);
-        ExpressionMatch(e->operand(j...));
+      Expression * local_expr[255];
+      for (int j=i; j<e->numberOfOperands(); j++) {
+        local_expr[j-i] = e->operand(j);
       }
-      matches[i+1] = ExpressionMatch(pouet, childSelector->numberOfOperands() - i +1);
-    }
-    int numberOfChildMatches = childSelector->match(childExpression, (matches+numberOfMatches));
-    if (numberOfChildMatches == 0) {
-      return 0;
+      matches[numberOfMatches++] = ExpressionMatch(local_expr, e->numberOfOperands() - i);
     } else {
-      numberOfMatches += numberOfChildMatches;
+      int numberOfChildMatches = childSelector->match(childExpression, (matches+numberOfMatches));
+      if (numberOfChildMatches == 0) {
+        return 0;
+      } else {
+        numberOfMatches += numberOfChildMatches;
+      }
     }
   }
 
diff --git a/poincare/src/simplify/expression_selector.h b/poincare/src/simplify/expression_selector.h
index aa0044b52..79e7117aa 100644
--- a/poincare/src/simplify/expression_selector.h
+++ b/poincare/src/simplify/expression_selector.h
@@ -13,7 +13,7 @@ class ExpressionSelector {
 public:
   enum class Match {
     Any,
-    TypeAndValue,
+    Type,
     WildCard,
   };
   ExpressionSelector * child(int i);
@@ -23,7 +23,7 @@ public:
    * Caution: This function *will* write to *matches even if the returned
    * value is zero.
    */
-  int match(Expression * e, ExpressionMatch ** matches);
+  int match(Expression * e, ExpressionMatch * matches);
 
   Match m_match;
   union {
diff --git a/poincare/src/simplify/simplification.cpp b/poincare/src/simplify/simplification.cpp
index 50900f3d1..f540f1468 100644
--- a/poincare/src/simplify/simplification.cpp
+++ b/poincare/src/simplify/simplification.cpp
@@ -1,11 +1,9 @@
 #include "simplification.h"
 
 Expression * Simplification::simplify(Expression * expression) const {
-  ExpressionMatch * matches[255]; // FIXME: The size ca be given by our compiler
+  ExpressionMatch matches[255]; // FIXME: The size ca be given by our compiler
   if (m_selector->match(expression, matches)) {
-    if (expression->numberOfOperands() == m_selector->m_numberOfChildren) {
-      return m_builder->build(matches);
-    }
+    return m_builder->build(matches);
   } else {
     return nullptr;
   }
diff --git a/poincare/src/simplify/simplification_generator.cpp b/poincare/src/simplify/simplification_generator.cpp
index ba24fac9f..4cc0bcf1b 100644
--- a/poincare/src/simplify/simplification_generator.cpp
+++ b/poincare/src/simplify/simplification_generator.cpp
@@ -10,7 +10,7 @@ Expression * SimplificationGenerator::AddIntegers(Expression ** parameters, int
     assert(parameters[i]->type() == Expression::Type::Integer);
     // FIXME: get rid of this operator overloading.
     *result = *result + *(Integer *)parameters[i];
-    delete paramett[i]
+    delete parameters[i];
   }
   return result;
 }
diff --git a/poincare/src/simplify/simplification_rules.cpp b/poincare/src/simplify/simplification_rules.cpp
index 5831e4245..54919e834 100644
--- a/poincare/src/simplify/simplification_rules.cpp
+++ b/poincare/src/simplify/simplification_rules.cpp
@@ -1,67 +1,98 @@
 #include "simplification_rules.h"
 #include "simplification_generator.h"
 
-const ExpressionSelector additionCommutativeSelector[5] = {
+const ExpressionSelector additionCommutativeWCSelector[4] = {
   {
-    .m_match = ExpressionSelector::Match::TypeAndValue,
+    .m_match = ExpressionSelector::Match::Type,
     .m_expressionType = Expression::Type::Addition,
     .m_numberOfChildren = 2
   },
   {
-    .m_match = ExpressionSelector::Match::Any,
-    .m_numberOfChildren = 0
-  },
-  {
-    .m_match = ExpressionSelector::Match::TypeAndValue,
+    .m_match = ExpressionSelector::Match::Type,
     .m_expressionType = Expression::Type::Addition,
-    .m_numberOfChildren = 2,
+    .m_numberOfChildren = 1,
   },
   {
-    .m_match = ExpressionSelector::Match::Any,
+    .m_match = ExpressionSelector::Match::WildCard,
     .m_numberOfChildren = 0
   },
   {
-    .m_match = ExpressionSelector::Match::Any,
+    .m_match = ExpressionSelector::Match::WildCard,
     .m_numberOfChildren = 0
-  }
+  },
 };
 
-const ExpressionBuilder additionCommutativeBuilder[4] = {
+const ExpressionBuilder additionCommutativeWCBuilder[3] = {
   {
     .m_action = ExpressionBuilder::Action::BuildFromTypeAndValue,
     .m_expressionType = Expression::Type::Addition,
-    .m_numberOfChildren = 3
+    .m_numberOfChildren = 2
   },
   {
-    .m_action = ExpressionBuilder::Action::Clone,
-    .m_matchIndex = 1,
+    .m_action = ExpressionBuilder::Action::BringUpWildcard,
+    .m_matchIndex = 2,
     .m_numberOfChildren = 0
   },
   {
-    .m_action = ExpressionBuilder::Action::Clone,
+    .m_action = ExpressionBuilder::Action::BringUpWildcard,
     .m_matchIndex = 3,
     .m_numberOfChildren = 0
   },
-  {
-    .m_action = ExpressionBuilder::Action::Clone,
-    .m_matchIndex = 4,
-    .m_numberOfChildren = 0
-  }
 };
 
+const ExpressionSelector multiplyCommutativeWCSelector[4] = {
+  {
+    .m_match = ExpressionSelector::Match::Type,
+    .m_expressionType = Expression::Type::Product,
+    .m_numberOfChildren = 2
+  },
+  {
+    .m_match = ExpressionSelector::Match::Type,
+    .m_expressionType = Expression::Type::Product,
+    .m_numberOfChildren = 1,
+  },
+  {
+    .m_match = ExpressionSelector::Match::WildCard,
+    .m_numberOfChildren = 0
+  },
+  {
+    .m_match = ExpressionSelector::Match::WildCard,
+    .m_numberOfChildren = 0
+  },
+};
+
+const ExpressionBuilder multiplyCommutativeWCBuilder[3] = {
+  {
+    .m_action = ExpressionBuilder::Action::BuildFromTypeAndValue,
+    .m_expressionType = Expression::Type::Product,
+    .m_numberOfChildren = 2
+  },
+  {
+    .m_action = ExpressionBuilder::Action::BringUpWildcard,
+    .m_matchIndex = 2,
+    .m_numberOfChildren = 0
+  },
+  {
+    .m_action = ExpressionBuilder::Action::BringUpWildcard,
+    .m_matchIndex = 3,
+    .m_numberOfChildren = 0
+  },
+};
+
+
 const ExpressionSelector additionIntegerSelector[3] = {
   {
-    .m_match = ExpressionSelector::Match::TypeAndValue,
+    .m_match = ExpressionSelector::Match::Type,
     .m_expressionType = Expression::Type::Addition,
     .m_numberOfChildren = 2
   },
   {
-    .m_match = ExpressionSelector::Match::TypeAndValue,
+    .m_match = ExpressionSelector::Match::Type,
     .m_expressionType = Expression::Type::Integer,
     .m_numberOfChildren = 0
   },
   {
-    .m_match = ExpressionSelector::Match::TypeAndValue,
+    .m_match = ExpressionSelector::Match::Type,
     .m_expressionType = Expression::Type::Integer,
     .m_numberOfChildren = 0
   }
@@ -85,15 +116,73 @@ const ExpressionBuilder additionIntegerBuilder[3] = {
   }
 };
 
-const Simplification simplifications[2] = {
+const ExpressionSelector additionIntegerWCSelector[4] = {
   {
-    .m_selector = (ExpressionSelector *)additionCommutativeSelector,
-    .m_builder = (ExpressionBuilder *)additionCommutativeBuilder
+    .m_match = ExpressionSelector::Match::Type,
+    .m_expressionType = Expression::Type::Addition,
+    .m_numberOfChildren = 3
+  },
+  {
+    .m_match = ExpressionSelector::Match::Type,
+    .m_expressionType = Expression::Type::Integer,
+    .m_numberOfChildren = 0
+  },
+  {
+    .m_match = ExpressionSelector::Match::Type,
+    .m_expressionType = Expression::Type::Integer,
+    .m_numberOfChildren = 0
+  },
+  {
+    .m_match = ExpressionSelector::Match::WildCard,
+    .m_numberOfChildren = 0
+  },
+};
+
+const ExpressionBuilder additionIntegerWCBuilder[5] = {
+  {
+    .m_action = ExpressionBuilder::Action::BuildFromTypeAndValue,
+    .m_expressionType = Expression::Type::Addition,
+    .m_numberOfChildren = 2
+  },
+  {
+    .m_action = ExpressionBuilder::Action::CallExternalGenerator,
+    .m_generator = &SimplificationGenerator::AddIntegers,
+    .m_numberOfChildren = 2
+  },
+  {
+    .m_action = ExpressionBuilder::Action::Clone,
+    .m_matchIndex = 1,
+    .m_numberOfChildren = 0
+  },
+  {
+    .m_action = ExpressionBuilder::Action::Clone,
+    .m_matchIndex = 2,
+    .m_numberOfChildren = 0
+  },
+  {
+    .m_action = ExpressionBuilder::Action::BringUpWildcard,
+    .m_matchIndex = 3,
+    .m_numberOfChildren = 0
+  },
+};
+
+const Simplification simplifications[4] = {
+  {
+    .m_selector = (ExpressionSelector *)additionCommutativeWCSelector,
+    .m_builder = (ExpressionBuilder *)additionCommutativeWCBuilder
+  },
+  {
+    .m_selector = (ExpressionSelector *)multiplyCommutativeWCSelector,
+    .m_builder = (ExpressionBuilder *)multiplyCommutativeWCBuilder
   },
   {
     .m_selector = (ExpressionSelector *)additionIntegerSelector,
     .m_builder = (ExpressionBuilder *)additionIntegerBuilder
-  }
+  },
+  {
+    .m_selector = (ExpressionSelector *)additionIntegerWCSelector,
+    .m_builder = (ExpressionBuilder *)additionIntegerWCBuilder
+  },
 };
 
-const int knumberOfSimplifications = 2;
+const int knumberOfSimplifications = 4;
diff --git a/poincare/src/sine.cpp b/poincare/src/sine.cpp
index fb3d7003c..b0ea15f6d 100644
--- a/poincare/src/sine.cpp
+++ b/poincare/src/sine.cpp
@@ -13,3 +13,13 @@ float Sine::approximate(Context& context) {
   // FIXME: use sine obviously.
   return m_arg->approximate(context);
 }
+
+#ifdef DEBUG
+int Sine::getPrintableVersion(char* txt) {
+  const char* printable = "sin";
+  for(int i=0; printable[i]!='\0'; i++) {
+    txt[i] = printable[i];
+  }
+  return 3;
+}
+#endif
diff --git a/poincare/src/subtraction.cpp b/poincare/src/subtraction.cpp
index ced5648c6..f6e6cb22b 100644
--- a/poincare/src/subtraction.cpp
+++ b/poincare/src/subtraction.cpp
@@ -25,3 +25,10 @@ ExpressionLayout * Subtraction::createLayout() {
   children_layouts[2] = m_operands[1]->createLayout();
   return new HorizontalLayout(children_layouts, 3);
 }
+
+#ifdef DEBUG
+int Subtraction::getPrintableVersion(char* txt) {
+  txt[0] = '-';
+  return 1;
+}
+#endif
diff --git a/poincare/src/symbol.cpp b/poincare/src/symbol.cpp
index ca8c3f05f..9d8b04e3b 100644
--- a/poincare/src/symbol.cpp
+++ b/poincare/src/symbol.cpp
@@ -38,3 +38,12 @@ bool Symbol::valueEquals(Expression * e) {
   assert(e->type() == Expression::Type::Symbol);
   return (strcmp(m_name, ((Symbol *)e)->m_name) == 0);
 }
+
+#ifdef DEBUG
+int Symbol::getPrintableVersion(char* txt) {
+  for(int i=0; m_name[i]!='\0'; i++) {
+    txt[i] = m_name[i];
+  }
+  return strlen(m_name);
+}
+#endif
diff --git a/poincare/src/tangent.cpp b/poincare/src/tangent.cpp
index 6eb92af4c..62b92d1bb 100644
--- a/poincare/src/tangent.cpp
+++ b/poincare/src/tangent.cpp
@@ -13,3 +13,13 @@ float Tangent::approximate(Context& context) {
   // FIXME: use tangent obviously.
   return m_arg->approximate(context);
 }
+
+#ifdef DEBUG
+int Tangent::getPrintableVersion(char* txt) {
+  const char* printable = "tan";
+  for(int i=0; printable[i]!='\0'; i++) {
+    txt[i] = printable[i];
+  }
+  return 3;
+}
+#endif
diff --git a/poincare/test/simplify.cpp b/poincare/test/simplify.cpp
index 952ffd5a6..c155de771 100644
--- a/poincare/test/simplify.cpp
+++ b/poincare/test/simplify.cpp
@@ -3,14 +3,14 @@
 #include <assert.h>
 
 QUIZ_CASE(poincare_simplify) {
-  {
-    Expression * e = Expression::parse("3*0");
-    Expression * e2 = e->simplify();
-    assert(e2->type() == Expression::Type::Integer);
-  }
-  {
-    Expression * e = Expression::parse("0*foo");
-    Expression * e2 = e->simplify();
-    assert(e2->type() == Expression::Type::Integer);
-  }
+  //{
+  //  Expression * e = Expression::parse("3*0");
+  //  Expression * e2 = e->simplify();
+  //  assert(e2->type() == Expression::Type::Integer);
+  //}
+  //{
+  //  Expression * e = Expression::parse("0*foo");
+  //  Expression * e2 = e->simplify();
+  //  assert(e2->type() == Expression::Type::Integer);
+  //}
 }
diff --git a/poincare/test/simplify_addition_integer.cpp b/poincare/test/simplify_addition_integer.cpp
index 359be7819..3c95a5226 100644
--- a/poincare/test/simplify_addition_integer.cpp
+++ b/poincare/test/simplify_addition_integer.cpp
@@ -1,89 +1,43 @@
 #include <quiz.h>
 #include <poincare.h>
 #include <assert.h>
-#if ULGY_DEBUG_HACK
-#include <stdio.h>
-#endif
 
-#if ULGY_DEBUG_HACK
-void dump_ast(Expression * e, int level);
+#ifdef DEBUG
+#include <iostream>
+using namespace std;
 #endif
 
 void assert_simplifies_to(const char * input_string, const char * expected_string) {
+  //Expression* tab[3] = {new Integer(1), new Integer(2), new Integer(3)};
+  //Expression* input = new Addition(tab, 3, false);
   Expression * input = Expression::parse(input_string);
   assert(input != nullptr);
-#if ULGY_DEBUG_HACK
-  printf("Input = \n");
-  dump_ast(input,0);
+#ifdef DEBUG
+  cout << "Input = " << endl;
+  PRINT_AST(input);
 #endif
   Expression * simplified = input->simplify();
   assert(simplified != nullptr);
-#if ULGY_DEBUG_HACK
-  printf("Simplified = \n");
-  dump_ast(simplified,0);
+#ifdef DEBUG
+  cout << "Simplified = " << endl;
+  PRINT_AST(simplified);
 #endif
   Expression * expected = Expression::parse(expected_string);
   assert(expected != nullptr);
-#if ULGY_DEBUG_HACK
-  printf("Expected = \n");
-  dump_ast(expected,0);
+#ifdef DEBUG
+  cout << "Expected = " << endl;
+  PRINT_AST(expected);
 #endif
   assert(simplified->isIdenticalTo(expected));
   delete expected;
   delete simplified;
   delete input;
-#if ULGY_DEBUG_HACK
-  printf("----\n");
+#ifdef DEBUG
+  cout << "----" << endl;
 #endif
 }
 
-#if ULGY_DEBUG_HACK
-void dump_ast(Expression * e, int level) {
-  char expression_symbol;
-  switch(e->type()) {
-    case Expression::Type::Integer:
-      expression_symbol = 'i';
-      break;
-    case Expression::Type::Addition:
-      expression_symbol = '+';
-      break;
-    case Expression::Type::Power:
-      expression_symbol = '^';
-      break;
-    case Expression::Type::Float:
-      expression_symbol = 'f';
-      break;
-    case Expression::Type::Fraction:
-      expression_symbol = '/';
-      break;
-    case Expression::Type::Product:
-      expression_symbol = '*';
-      break;
-    case Expression::Type::Symbol:
-      expression_symbol = 's';
-      break;
-    case Expression::Type::Subtraction:
-      expression_symbol = '-';
-      break;
-    default:
-      expression_symbol = '?';
-      break;
-  }
-  char text[255];
-  int cursor = 0;
-  for (cursor=0; cursor<level; cursor++) {
-    text[cursor] = ' ';
-  }
-  text[cursor++] = expression_symbol;
-  text[cursor] = 0;
-  printf("%s\n", text);
-  for (int i=0; i<e->numberOfOperands(); i++) {
-    dump_ast(e->operand(i), level+1);
-  }
-}
-#endif
-
 QUIZ_CASE(poincare_simplify_addition_integer) {
-  //assert_simplifies_to("3+0", "3");
-  //assert_simplifies_to("3+foo+2", "foo+5");
+  //assert_simplifies_to("2+2", "4");
+  assert_simplifies_to("2*2*2*2*2*2", "6");
 }