diff --git a/poincare/include/poincare/expression.h b/poincare/include/poincare/expression.h
index 3d5940e45..b99621c2a 100644
--- a/poincare/include/poincare/expression.h
+++ b/poincare/include/poincare/expression.h
@@ -12,6 +12,7 @@ typedef void (Expression::*ExpressionAction)(void);
 
 class Expression {
   public:
+    static Expression * parse(char * string);
     void recursiveDraw();
     void recursiveLayout();
     KDRect m_frame;
diff --git a/poincare/src/expression.cpp b/poincare/src/expression.cpp
index f4eb90ce6..70182352e 100644
--- a/poincare/src/expression.cpp
+++ b/poincare/src/expression.cpp
@@ -4,7 +4,7 @@
 
 int poincare_expression_yyparse(yyscan_t scanner, Expression ** expressionOutput);
 
-void CreateFromString(char * string) {
+Expression * Expression::parse(char * string) {
   yyscan_t scanner;
   YY_BUFFER_STATE buf;
   poincare_expression_yylex_init(&scanner);
@@ -13,12 +13,16 @@ void CreateFromString(char * string) {
   poincare_expression_yyparse(scanner, &expression);
 
 
-  expression->recursiveLayout();
-  expression->m_frame.origin = KDPOINT(0, 100);
-  expression->recursiveDraw();
-
   poincare_expression_yy_delete_buffer(buf, scanner);
   poincare_expression_yylex_destroy(scanner);
+
+  return expression;
+}
+
+bool Expression::identicalTo(Expression * e) {
+  // By default, two expression are not identical.
+  // This should obviously be overriden in subclasses!
+  return false;
 }
 
 
diff --git a/src/hello.cpp b/src/hello.cpp
index 9f9213f2e..34e4b2f1d 100644
--- a/src/hello.cpp
+++ b/src/hello.cpp
@@ -16,7 +16,11 @@ void hello() {
     if (character == '.') {
       input[index] = 0;
       index = 0;
-      CreateFromString(input);
+      Expression * e = Expression::parse(input);
+      e->recursiveLayout();
+      e->m_frame.origin = KDPOINT(0, 100);
+      e->recursiveDraw();
+      //FIXME delete e;
     } else {
       if (index == 0) {
         KDFillRect((KDRect){