diff --git a/poincare/include/poincare/expression.h b/poincare/include/poincare/expression.h
index e6699ca1a..142b8966a 100644
--- a/poincare/include/poincare/expression.h
+++ b/poincare/include/poincare/expression.h
@@ -297,6 +297,7 @@ protected:
 
   /* Hierarchy */
   Expression parent() const; // TODO try to inline
+  Expression replaceWithUndefinedInPlace();
   void defaultSetChildrenInPlace(Expression other);
   void addChildAtIndexInPlace(TreeHandle t, int index, int currentNumberOfChildren) = delete;
   void removeChildAtIndexInPlace(int i) = delete;
diff --git a/poincare/src/addition.cpp b/poincare/src/addition.cpp
index b2b316994..f949c068a 100644
--- a/poincare/src/addition.cpp
+++ b/poincare/src/addition.cpp
@@ -175,9 +175,7 @@ Expression Addition::shallowReduce(ExpressionNode::ReductionContext reductionCon
       /* If there is a matrix in the children, the last child is a matrix. If
        * there is a ascalar, the first child is a scalar.
        * We forbid the addition of a matrix and a scalar. */
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
     // Create the addition matrix (in place of the first child)
     Matrix resultMatrix = static_cast<Matrix &>(firstChild);
@@ -191,9 +189,7 @@ Expression Addition::shallowReduce(ExpressionNode::ReductionContext reductionCon
       int currentM = currentMatrix.numberOfColumns();
       if (currentN != n || currentM != m) {
         // Addition of matrices of different dimensions -> undef
-        Expression result = Undefined::Builder();
-        replaceWithInPlace(result);
-        return result;
+        return replaceWithUndefinedInPlace();
       }
       // Dispatch the current matrix children in the created addition matrix
       for (int j = 0; j < n*m; j++) {
diff --git a/poincare/src/binomial_coefficient.cpp b/poincare/src/binomial_coefficient.cpp
index 343de9a9e..51f83857d 100644
--- a/poincare/src/binomial_coefficient.cpp
+++ b/poincare/src/binomial_coefficient.cpp
@@ -65,25 +65,19 @@ Expression BinomialCoefficient::shallowReduce(Context * context) {
   Expression c1 = childAtIndex(1);
 
   if (SortedIsMatrix(c0, context) || SortedIsMatrix(c1, context)) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
 
   if (c0.type() == ExpressionNode::Type::Rational) {
     Rational r0 = static_cast<Rational&>(c0);
     if (!r0.integerDenominator().isOne() || r0.isNegative()) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c1.type() == ExpressionNode::Type::Rational) {
     Rational r1 = static_cast<Rational&>(c1);
     if (!r1.integerDenominator().isOne() || r1.isNegative()) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c0.type() != ExpressionNode::Type::Rational || c1.type() != ExpressionNode::Type::Rational) {
@@ -95,9 +89,7 @@ Expression BinomialCoefficient::shallowReduce(Context * context) {
   Integer n = r0.signedIntegerNumerator();
   Integer k = r1.signedIntegerNumerator();
   if (n.isLowerThan(k)) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   /* If n is too big, we do not reduce in order to avoid too long computation.
    * The binomial coefficient will be approximatively evaluated later. */
diff --git a/poincare/src/confidence_interval.cpp b/poincare/src/confidence_interval.cpp
index db026ccd6..a0439125c 100644
--- a/poincare/src/confidence_interval.cpp
+++ b/poincare/src/confidence_interval.cpp
@@ -62,24 +62,18 @@ Expression ConfidenceInterval::shallowReduce(ExpressionNode::ReductionContext re
   Expression c0 = childAtIndex(0);
   Expression c1 = childAtIndex(1);
   if (SortedIsMatrix(c0, reductionContext.context()) || SortedIsMatrix(c1, reductionContext.context())) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   if (c0.type() == ExpressionNode::Type::Rational) {
     Rational r0 = static_cast<Rational&>(c0);
     if (r0.signedIntegerNumerator().isNegative() || Integer::NaturalOrder(r0.signedIntegerNumerator(), r0.integerDenominator()) > 0) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c1.type() == ExpressionNode::Type::Rational) {
     Rational r1 = static_cast<Rational&>(c1);
     if (!r1.integerDenominator().isOne() || r1.signedIntegerNumerator().isNegative()) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c0.type() != ExpressionNode::Type::Rational || c1.type() != ExpressionNode::Type::Rational) {
diff --git a/poincare/src/derivative.cpp b/poincare/src/derivative.cpp
index 52cb396ce..99e821b13 100644
--- a/poincare/src/derivative.cpp
+++ b/poincare/src/derivative.cpp
@@ -146,9 +146,7 @@ Expression Derivative::shallowReduce(Context * context) {
       || SortedIsMatrix(childAtIndex(1), context)
       || SortedIsMatrix(childAtIndex(2), context))
   {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   // TODO: to be implemented diff(+) -> +diff() etc
   return *this;
diff --git a/poincare/src/division_quotient.cpp b/poincare/src/division_quotient.cpp
index f62a6b240..cffae83bc 100644
--- a/poincare/src/division_quotient.cpp
+++ b/poincare/src/division_quotient.cpp
@@ -46,24 +46,18 @@ Expression DivisionQuotient::shallowReduce() {
   Expression c0 = childAtIndex(0);
   Expression c1 = childAtIndex(1);
   if (c0.type() == ExpressionNode::Type::Matrix || c1.type() == ExpressionNode::Type::Matrix) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   if (c0.type() == ExpressionNode::Type::Rational) {
     Rational r0 = static_cast<Rational &>(c0);
     if (!r0.integerDenominator().isOne()) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c1.type() == ExpressionNode::Type::Rational) {
     Rational r1 = static_cast<Rational &>(c1);
     if (!r1.integerDenominator().isOne()) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c0.type() != ExpressionNode::Type::Rational || c1.type() != ExpressionNode::Type::Rational) {
diff --git a/poincare/src/division_remainder.cpp b/poincare/src/division_remainder.cpp
index 9f0f13c01..14b5723ec 100644
--- a/poincare/src/division_remainder.cpp
+++ b/poincare/src/division_remainder.cpp
@@ -47,24 +47,18 @@ Expression DivisionRemainder::shallowReduce() {
   Expression c0 = childAtIndex(0);
   Expression c1 = childAtIndex(1);
   if (c0.type() == ExpressionNode::Type::Matrix || c1.type() == ExpressionNode::Type::Matrix) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   if (c0.type() == ExpressionNode::Type::Rational) {
     Rational r0 = static_cast<Rational &>(c0);
     if (!r0.integerDenominator().isOne()) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c1.type() == ExpressionNode::Type::Rational) {
     Rational r1 = static_cast<Rational &>(c1);
     if (!r1.integerDenominator().isOne()) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c0.type() != ExpressionNode::Type::Rational || c1.type() != ExpressionNode::Type::Rational) {
diff --git a/poincare/src/expression.cpp b/poincare/src/expression.cpp
index 9b98414b7..d881bb6e3 100644
--- a/poincare/src/expression.cpp
+++ b/poincare/src/expression.cpp
@@ -1,9 +1,9 @@
 #include <poincare/expression.h>
 #include <poincare/expression_node.h>
-#include <poincare/rational.h>
 #include <poincare/opposite.h>
-#include <poincare/undefined.h>
+#include <poincare/rational.h>
 #include <poincare/symbol.h>
+#include <poincare/undefined.h>
 #include <poincare/variable_context.h>
 #include <ion.h>
 #include <ion/unicode/utf8_helper.h>
@@ -240,6 +240,12 @@ Expression Expression::parent() const {
   return static_cast<Expression &>(p);
 }
 
+Expression Expression::replaceWithUndefinedInPlace() {
+  Expression result = Undefined::Builder();
+  replaceWithInPlace(result);
+  return result;
+}
+
 void Expression::defaultSetChildrenInPlace(Expression other) {
   assert(numberOfChildren() == other.numberOfChildren());
   for (int i = 0; i < numberOfChildren(); i++) {
diff --git a/poincare/src/factor.cpp b/poincare/src/factor.cpp
index 52b67dfd4..059f7091b 100644
--- a/poincare/src/factor.cpp
+++ b/poincare/src/factor.cpp
@@ -67,9 +67,7 @@ Expression Factor::shallowReduce() {
     }
   }
   if (childAtIndex(0).type() == ExpressionNode::Type::Matrix) { // TODO LEA SortedIsMatrix?
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   return *this;
 }
@@ -77,9 +75,7 @@ Expression Factor::shallowReduce() {
 Expression Factor::shallowBeautify(ExpressionNode::ReductionContext reductionContext) {
   Expression c = childAtIndex(0);
   if (c.type() != ExpressionNode::Type::Rational) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   Rational r = static_cast<Rational &>(c);
   if (r.isZero()) {
@@ -88,17 +84,13 @@ Expression Factor::shallowBeautify(ExpressionNode::ReductionContext reductionCon
   }
   Multiplication numeratorDecomp = createMultiplicationOfIntegerPrimeDecomposition(r.unsignedIntegerNumerator(), reductionContext.context(), reductionContext.complexFormat(), reductionContext.angleUnit());
   if (numeratorDecomp.numberOfChildren() == 0) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   Expression result = numeratorDecomp.squashUnaryHierarchyInPlace();
   if (!r.integerDenominator().isOne()) {
     Multiplication denominatorDecomp = createMultiplicationOfIntegerPrimeDecomposition(r.integerDenominator(), reductionContext.context(), reductionContext.complexFormat(), reductionContext.angleUnit());
     if (denominatorDecomp.numberOfChildren() == 0) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
     result = Division::Builder(result, denominatorDecomp.squashUnaryHierarchyInPlace());
   }
diff --git a/poincare/src/factorial.cpp b/poincare/src/factorial.cpp
index f5f6c5a64..5e12fa7cb 100644
--- a/poincare/src/factorial.cpp
+++ b/poincare/src/factorial.cpp
@@ -91,9 +91,7 @@ Expression Factorial::shallowReduce(ExpressionNode::ReductionContext reductionCo
   if (c.type() == ExpressionNode::Type::Rational) {
     Rational r = c.convert<Rational>();
     if (!r.integerDenominator().isOne() || r.sign() == ExpressionNode::Sign::Negative) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
     if (Integer(k_maxOperandValue).isLowerThan(r.unsignedIntegerNumerator())) {
       return *this;
@@ -105,9 +103,7 @@ Expression Factorial::shallowReduce(ExpressionNode::ReductionContext reductionCo
   }
   if (c.type() == ExpressionNode::Type::Constant) {
     // e! = undef, i! = undef, pi! = undef
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   return *this;
 }
diff --git a/poincare/src/function.cpp b/poincare/src/function.cpp
index d7e98e09b..25ddbeb38 100644
--- a/poincare/src/function.cpp
+++ b/poincare/src/function.cpp
@@ -138,9 +138,7 @@ Expression Function::shallowReduce(ExpressionNode::ReductionContext reductionCon
     return e.deepReduce(reductionContext);
   }
   if (!reductionContext.symbolicComputation()) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   return *this;
 }
diff --git a/poincare/src/great_common_divisor.cpp b/poincare/src/great_common_divisor.cpp
index 2086df496..32ee6155c 100644
--- a/poincare/src/great_common_divisor.cpp
+++ b/poincare/src/great_common_divisor.cpp
@@ -60,24 +60,18 @@ Expression GreatCommonDivisor::shallowReduce() {
   Expression c0 = childAtIndex(0);
   Expression c1 = childAtIndex(1);
   if (c0.type() == ExpressionNode::Type::Matrix || c1.type() == ExpressionNode::Type::Matrix) { //TODO LEA SortedIsMatrix ?
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   if (c0.type() == ExpressionNode::Type::Rational) {
     Rational r0 = static_cast<Rational &>(c0);
     if (!r0.integerDenominator().isOne()) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c1.type() == ExpressionNode::Type::Rational) {
     Rational r1 = static_cast<Rational&>(c1);
     if (!r1.integerDenominator().isOne()) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c0.type() != ExpressionNode::Type::Rational || c1.type() != ExpressionNode::Type::Rational) {
diff --git a/poincare/src/integral.cpp b/poincare/src/integral.cpp
index 6542fe855..661bfa879 100644
--- a/poincare/src/integral.cpp
+++ b/poincare/src/integral.cpp
@@ -225,9 +225,7 @@ Expression Integral::shallowReduce(Context * context) {
       || SortedIsMatrix(childAtIndex(2), context)
       || SortedIsMatrix(childAtIndex(3), context))
   {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   return *this;
 }
diff --git a/poincare/src/least_common_multiple.cpp b/poincare/src/least_common_multiple.cpp
index af091c500..33a32fdc9 100644
--- a/poincare/src/least_common_multiple.cpp
+++ b/poincare/src/least_common_multiple.cpp
@@ -64,24 +64,18 @@ Expression LeastCommonMultiple::shallowReduce() {
   Expression c0 = childAtIndex(0);
   Expression c1 = childAtIndex(1);
   if (c0.type() == ExpressionNode::Type::Matrix || c1.type() == ExpressionNode::Type::Matrix) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   if (c0.type() == ExpressionNode::Type::Rational) {
     Rational r0 = static_cast<Rational &>(c0);
     if (!r0.integerDenominator().isOne()) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c1.type() == ExpressionNode::Type::Rational) {
     Rational r1 = static_cast<Rational &>(c1);
     if (!r1.integerDenominator().isOne()) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c0.type() != ExpressionNode::Type::Rational || c1.type() != ExpressionNode::Type::Rational) {
diff --git a/poincare/src/logarithm.cpp b/poincare/src/logarithm.cpp
index 7d2387362..2386e4084 100644
--- a/poincare/src/logarithm.cpp
+++ b/poincare/src/logarithm.cpp
@@ -111,9 +111,7 @@ Expression Logarithm::shallowReduce(ExpressionNode::ReductionContext reductionCo
   }
 
   if (SortedIsMatrix(childAtIndex(1), reductionContext.context())) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
 
   Expression c = childAtIndex(0);
@@ -220,15 +218,11 @@ Expression Logarithm::simpleShallowReduce(Context * context, Preferences::Comple
   Expression b = childAtIndex(1);
   // log(0,0)->Undefined
   if (c.type() == ExpressionNode::Type::Rational && b.type() == ExpressionNode::Type::Rational && static_cast<Rational &>(b).isZero() && static_cast<Rational &>(c).isZero()) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   // log(x,1)->Undefined
   if (b.type() == ExpressionNode::Type::Rational && static_cast<Rational &>(b).isOne()) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   bool infiniteArg = c.recursivelyMatches(Expression::IsInfinity, context);
   // log(x,x)->1 with x != inf and log(inf,inf) = undef
@@ -251,9 +245,7 @@ Expression Logarithm::simpleShallowReduce(Context * context, Preferences::Comple
       bool infiniteBase = b.recursivelyMatches(Expression::IsInfinity, context);
       // Special case: log(0,inf) -> undef
       if (infiniteBase) {
-        Expression result = Undefined::Builder();
-        replaceWithInPlace(result);
-        return result;
+        return replaceWithUndefinedInPlace();
       }
       bool isNegative = true;
       Expression result;
diff --git a/poincare/src/matrix_identity.cpp b/poincare/src/matrix_identity.cpp
index 79f6112e8..c015030d8 100644
--- a/poincare/src/matrix_identity.cpp
+++ b/poincare/src/matrix_identity.cpp
@@ -47,22 +47,19 @@ Expression MatrixIdentity::shallowReduce(ExpressionNode::ReductionContext reduct
     if (e.isUndefined()) {
       return e;
     }
-
-    Expression c = childAtIndex(0);
-    if (!c.isRationalOne()) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
-    }
-    Integer dimension = static_cast<Rational &>(c).signedIntegerNumerator();
-    if (Integer::NaturalOrder(dimension, Integer(Integer::k_maxExtractableInteger)) > 0) {
-      return *this;
-    }
-    int dim = dimension.extractedInt();
-    Expression result = Matrix::CreateIdentity(dim);
-    replaceWithInPlace(result);
-    return result;
   }
+  Expression c = childAtIndex(0);
+  if (!c.isRationalOne()) {
+    return replaceWithUndefinedInPlace();
+  }
+  Integer dimension = static_cast<Rational &>(c).signedIntegerNumerator();
+  if (Integer::NaturalOrder(dimension, Integer(Integer::k_maxExtractableInteger)) > 0) {
+    return *this;
+  }
+  int dim = dimension.extractedInt();
+  Expression result = Matrix::CreateIdentity(dim);
+  replaceWithInPlace(result);
+  return result;
 }
 
 }
diff --git a/poincare/src/multiplication.cpp b/poincare/src/multiplication.cpp
index 3bfdbc1ab..c3c8bf636 100644
--- a/poincare/src/multiplication.cpp
+++ b/poincare/src/multiplication.cpp
@@ -297,9 +297,7 @@ Expression Multiplication::privateShallowReduce(ExpressionNode::ReductionContext
       int currentM = currentMatrix.numberOfColumns();
       if (currentM != n) {
         // Matrices dimensions do not match for multiplication
-        Expression result = Undefined::Builder();
-        replaceWithInPlace(result);
-        return result;
+        return replaceWithUndefinedInPlace();
       }
       /* Create the matrix resulting of the multiplication of the current matrix
        * and the result matrix
diff --git a/poincare/src/nth_root.cpp b/poincare/src/nth_root.cpp
index 1a577dbe3..a3bddbf73 100644
--- a/poincare/src/nth_root.cpp
+++ b/poincare/src/nth_root.cpp
@@ -72,9 +72,7 @@ Expression NthRoot::shallowReduce(ExpressionNode::ReductionContext reductionCont
     }
   }
   if (childAtIndex(0).type() == ExpressionNode::Type::Matrix || childAtIndex(1).type() == ExpressionNode::Type::Matrix) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   Expression invIndex = Power::Builder(childAtIndex(1), Rational::Builder(-1));
   Power p = Power::Builder(childAtIndex(0), invIndex);
diff --git a/poincare/src/permute_coefficient.cpp b/poincare/src/permute_coefficient.cpp
index 459636603..62e0d66c8 100644
--- a/poincare/src/permute_coefficient.cpp
+++ b/poincare/src/permute_coefficient.cpp
@@ -60,24 +60,18 @@ Expression PermuteCoefficient::shallowReduce() {
   Expression c0 = childAtIndex(0);
   Expression c1 = childAtIndex(1);
   if (c0.type() == ExpressionNode::Type::Matrix || c1.type() == ExpressionNode::Type::Matrix) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   if (c0.type() == ExpressionNode::Type::Rational) {
     Rational r0 = static_cast<Rational &>(c0);
     if (!r0.integerDenominator().isOne() || r0.sign() == ExpressionNode::Sign::Negative) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c1.type() == ExpressionNode::Type::Rational) {
     Rational r1 = static_cast<Rational &>(c1);
     if (!r1.integerDenominator().isOne() || r1.sign() == ExpressionNode::Sign::Negative) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c0.type() != ExpressionNode::Type::Rational || c1.type() != ExpressionNode::Type::Rational) {
diff --git a/poincare/src/power.cpp b/poincare/src/power.cpp
index 71107ed3c..48f4e35d3 100644
--- a/poincare/src/power.cpp
+++ b/poincare/src/power.cpp
@@ -292,9 +292,7 @@ Expression Power::shallowReduce(ExpressionNode::ReductionContext reductionContex
 
   // Step 0: Handle matrices
   if (index.type() == ExpressionNode::Type::Matrix) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   if (base.type() == ExpressionNode::Type::Matrix) {
     Matrix matrixBase = static_cast<Matrix &>(base);
@@ -302,9 +300,7 @@ Expression Power::shallowReduce(ExpressionNode::ReductionContext reductionContex
         || !static_cast<Rational &>(index).integerDenominator().isOne()
         || matrixBase.numberOfRows() != matrixBase.numberOfColumns())
     {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
     Integer exponent = static_cast<Rational &>(index).signedIntegerNumerator();
     if (exponent.isNegative()) {
@@ -359,9 +355,7 @@ Expression Power::shallowReduce(ExpressionNode::ReductionContext reductionContex
     if (b.isZero()) {
       // 0^0 = undef or (±inf)^0 = undef
       if ((childAtIndex(0).type() == ExpressionNode::Type::Rational && childAtIndex(0).convert<Rational>().isZero()) || childAtIndex(0).type() == ExpressionNode::Type::Infinity) {
-        Expression result = Undefined::Builder();
-        replaceWithInPlace(result);
-        return result;
+        return replaceWithUndefinedInPlace();
       }
       // x^0
       if (reductionContext.target() == ExpressionNode::ReductionTarget::User || childAtIndex(0).isNumber()) {
@@ -393,9 +387,7 @@ Expression Power::shallowReduce(ExpressionNode::ReductionContext reductionContex
       }
       // 0^x with x < 0 = undef
       if (childAtIndex(1).sign(reductionContext.context()) == ExpressionNode::Sign::Negative) {
-        Expression result = Undefined::Builder();
-        replaceWithInPlace(result);
-        return result;
+        return replaceWithUndefinedInPlace();
       }
     }
     // 1^x = 1 if x != ±inf
diff --git a/poincare/src/prediction_interval.cpp b/poincare/src/prediction_interval.cpp
index cf67a1d87..dee435bbb 100644
--- a/poincare/src/prediction_interval.cpp
+++ b/poincare/src/prediction_interval.cpp
@@ -57,24 +57,18 @@ Expression PredictionInterval::shallowReduce(ExpressionNode::ReductionContext re
   Expression c0 = childAtIndex(0);
   Expression c1 = childAtIndex(1);
   if (c0.type() == ExpressionNode::Type::Matrix || c1.type() == ExpressionNode::Type::Matrix) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   if (c0.type() == ExpressionNode::Type::Rational) {
     Rational r0 = static_cast<Rational &>(c0);
     if (r0.sign() == ExpressionNode::Sign::Negative || Integer::NaturalOrder(r0.unsignedIntegerNumerator(), r0.integerDenominator()) > 0) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c1.type() == ExpressionNode::Type::Rational) {
     Rational r1 = static_cast<Rational &>(c1);
     if (!r1.integerDenominator().isOne() || r1.sign() == ExpressionNode::Sign::Negative) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
   }
   if (c0.type() != ExpressionNode::Type::Rational || c1.type() != ExpressionNode::Type::Rational) {
@@ -83,9 +77,7 @@ Expression PredictionInterval::shallowReduce(ExpressionNode::ReductionContext re
   Rational r0 = static_cast<Rational &>(c0);
   Rational r1 = static_cast<Rational &>(c1);
   if (!r1.integerDenominator().isOne() || r1.sign() == ExpressionNode::Sign::Negative || r0.sign() == ExpressionNode::Sign::Negative || Integer::NaturalOrder(r0.unsignedIntegerNumerator(), r0.integerDenominator()) > 0) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   /* [r0-1.96*sqrt(r0*(1-r0)/r1), r0+1.96*sqrt(r0*(1-r0)/r1)]*/
   // Compute numerator = r0*(1-r0)
diff --git a/poincare/src/round.cpp b/poincare/src/round.cpp
index 6895d0fec..ea6f8ae1b 100644
--- a/poincare/src/round.cpp
+++ b/poincare/src/round.cpp
@@ -46,9 +46,7 @@ Expression Round::shallowReduce(ExpressionNode::ReductionContext reductionContex
     }
   }
   if (childAtIndex(1).type() == ExpressionNode::Type::Matrix) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   if (childAtIndex(0).type() == ExpressionNode::Type::Matrix) {
     return mapOnMatrixFirstChild(reductionContext);
@@ -59,9 +57,7 @@ Expression Round::shallowReduce(ExpressionNode::ReductionContext reductionContex
     Rational r1 = childAtIndex(0).convert<Rational>();
     Rational r2 = childAtIndex(1).convert<Rational>();
     if (!r2.integerDenominator().isOne()) {
-      Expression result = Undefined::Builder();
-      replaceWithInPlace(result);
-      return result;
+      return replaceWithUndefinedInPlace();
     }
     const Rational ten = Rational::Builder(10);
     if (Power::RationalExponentShouldNotBeReduced(ten, r2)) {
diff --git a/poincare/src/sequence.cpp b/poincare/src/sequence.cpp
index 693878760..c6dd14e2f 100644
--- a/poincare/src/sequence.cpp
+++ b/poincare/src/sequence.cpp
@@ -56,9 +56,7 @@ Expression Sequence::shallowReduce() {
   }
   assert(childAtIndex(1).type() != ExpressionNode::Type::Matrix);
   if (childAtIndex(2).type() == ExpressionNode::Type::Matrix || childAtIndex(3).type() == ExpressionNode::Type::Matrix) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   return *this;
 }
diff --git a/poincare/src/sign_function.cpp b/poincare/src/sign_function.cpp
index 5a0c30504..dc8549513 100644
--- a/poincare/src/sign_function.cpp
+++ b/poincare/src/sign_function.cpp
@@ -63,9 +63,7 @@ Expression SignFunction::shallowReduce(ExpressionNode::ReductionContext reductio
   }
   Expression child = childAtIndex(0);
   if (child.type() == ExpressionNode::Type::Matrix) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   Rational resultSign = Rational::Builder(1);
   ExpressionNode::Sign s = child.sign(reductionContext.context());
diff --git a/poincare/src/square_root.cpp b/poincare/src/square_root.cpp
index 7aef0720b..f49603a0e 100644
--- a/poincare/src/square_root.cpp
+++ b/poincare/src/square_root.cpp
@@ -52,9 +52,7 @@ Expression SquareRoot::shallowReduce(ExpressionNode::ReductionContext reductionC
   }
   Expression c = childAtIndex(0);
   if (c.type() == ExpressionNode::Type::Matrix) {
-    Expression result = Undefined::Builder();
-    replaceWithInPlace(result);
-    return result;
+    return replaceWithUndefinedInPlace();
   }
   Power p = Power::Builder(c, Rational::Builder(1, 2));
   replaceWithInPlace(p);