diff --git a/src/script/dependency.cpp b/src/script/dependency.cpp
index 911dda1a..60edc8f1 100644
--- a/src/script/dependency.cpp
+++ b/src/script/dependency.cpp
@@ -22,11 +22,11 @@ extern ScriptValueP dependency_dummy;
 // A dummy type used during dependency analysis,
 // it simply supresses all error messages.
 class DependencyDummy : public ScriptIterator {
-  public:
-  virtual ScriptType type() const { return SCRIPT_DUMMY; }
-  virtual String typeName() const { return _("dummy"); }
-  virtual ScriptValueP next(ScriptValueP*) { return ScriptValueP(); }
-  virtual ScriptValueP dependencyName(const ScriptValue&, const Dependency&) const { return dependency_dummy; }
+public:
+  ScriptType type() const override { return SCRIPT_DUMMY; }
+  String typeName() const override { return _("dummy"); }
+  ScriptValueP next(ScriptValueP*,int*) override { return ScriptValueP(); }
+  ScriptValueP dependencyName(const ScriptValue&, const Dependency&) const override { return dependency_dummy; }
 };
 
 ScriptValueP dependency_dummy(new DependencyDummy);
@@ -43,19 +43,19 @@ public:
     : a(a), b(b)
   {}
   
-  virtual ScriptType type() const { return SCRIPT_DUMMY; }
-  virtual String typeName() const { return _("union of ") + a->typeName() + _(" and ") + b->typeName(); }
+  ScriptType type() const override { return SCRIPT_DUMMY; }
+  String typeName() const override { return _("union of ") + a->typeName() + _(" and ") + b->typeName(); }
   
-  virtual ScriptValueP dependencies(Context& ctx, const Dependency& dep) const {
+  ScriptValueP dependencies(Context& ctx, const Dependency& dep) const override {
     return unified( a->dependencies(ctx,dep), b->dependencies(ctx,dep));
   }
-  virtual ScriptValueP makeIterator(ScriptValueP thisP) const {
+  ScriptValueP makeIterator(const ScriptValueP& thisP) const override {
     return unified(a->makeIterator(a), b->makeIterator(b));
   }
-  virtual ScriptValueP dependencyMember(const String& name, const Dependency& dep) const {
+  ScriptValueP dependencyMember(const String& name, const Dependency& dep) const override {
     return unified(a->dependencyMember(name,dep), b->dependencyMember(name,dep));
   }
-  virtual ScriptValueP dependencyName(const ScriptValue& container, const Dependency& dep) const {
+  ScriptValueP dependencyName(const ScriptValue& container, const Dependency& dep) const override {
     return unified(a->dependencyName(container,dep), b->dependencyName(container,dep));
   }
 private:
diff --git a/src/script/to_value.hpp b/src/script/to_value.hpp
index 2f1c1d87..82163aca 100644
--- a/src/script/to_value.hpp
+++ b/src/script/to_value.hpp
@@ -75,7 +75,7 @@ struct ScriptIterator : public ScriptValue {
   CompareWhat compareAs(String&, void const*&) const override;
 
   /// Return the next item for this iterator, or ScriptValueP() if there is no such item
-  ScriptValueP next(ScriptValueP* key_out = nullptr) override = 0;
+  ScriptValueP next(ScriptValueP* key_out = nullptr, int* index_out = nullptr) override = 0;
   ScriptValueP makeIterator(const ScriptValueP& thisP) const override;
 };
 
@@ -98,9 +98,10 @@ template <typename Collection>
 class ScriptCollectionIterator : public ScriptIterator {
 public:
   ScriptCollectionIterator(const Collection* col) : pos(0), col(col) {}
-  ScriptValueP next(ScriptValueP* key_out) override {
+  ScriptValueP next(ScriptValueP* key_out, int* index_out) override {
     if (pos < col->size()) {
       if (key_out) *key_out = to_script((int)pos);
+      if (index_out) *index_out = (int)pos;
       return to_script(col->at(pos++));
     } else {
       return ScriptValueP();
diff --git a/src/script/value.cpp b/src/script/value.cpp
index a64f0ca1..1b8d9ece 100644
--- a/src/script/value.cpp
+++ b/src/script/value.cpp
@@ -46,7 +46,7 @@ ScriptValueP ScriptValue::eval(Context&, bool) const {
   return delay_error(ScriptErrorConversion(typeName(), _TYPE_("function")));
 }
 
-ScriptValueP ScriptValue::next(ScriptValueP* key_out) {
+ScriptValueP ScriptValue::next(ScriptValueP* key_out, int* index_out) {
   throw InternalError(_("Can't convert from ")+typeName()+_(" to iterator"));
 }
 ScriptValueP ScriptValue::makeIterator(const ScriptValueP&) const {
@@ -183,9 +183,10 @@ public:
   ScriptRangeIterator(int start, int end)
     : pos(start), start(start), end(end)
   {}
-  ScriptValueP next(ScriptValueP* key_out) override {
+  ScriptValueP next(ScriptValueP* key_out, int* index_out) override {
     if (pos <= end) {
       if (key_out) *key_out = to_script(pos-start);
+      if (index_out) *index_out = (int)pos;
       return to_script(pos++);
     } else {
       return ScriptValueP();
@@ -288,6 +289,22 @@ ScriptValueP to_script(double v) {
 
 // ----------------------------------------------------------------------------- : String type
 
+String quote_string(String const& str) {
+  String out;
+  out.reserve(str.size() + 2);
+  out += _('"');
+  FOR_EACH_CONST(c, str) {
+    if      (c == _('"') || c == _('\\')) { out += _('\\'); out += c; }
+    else if (c == _('\1')) out += _("\\<");
+    else if (c == _('\n')) out += _("\\n");
+    else if (c == _('\r')) out += _("\\r");
+    else if (c == _('\t')) out += _("\\t");
+    else out += c;
+  }
+  out += _('"');
+  return out;
+}
+
 // String values
 class ScriptString : public ScriptValue {
 public:
@@ -295,6 +312,9 @@ public:
   ScriptType type() const override { return SCRIPT_STRING; }
   String typeName() const override { return _TYPE_("string") + _(" (\"") + (value.size() < 30 ? value : value.substr(0,30) + _("...")) + _("\")"); }
   String toString() const override { return value; }
+  String toCode() const override {
+    return quote_string(value);
+  }
   double toDouble() const override {
     double d;
     if (value.ToDouble(&d)) {
@@ -437,10 +457,15 @@ String ScriptCollectionBase::toCode() const {
   String ret = _("[");
   bool first = true;
   ScriptValueP it = makeIterator();
-  while (ScriptValueP v = it->next()) {
+  ScriptValueP key;
+  int index = -1;
+  while (ScriptValueP v = it->next(&key,&index)) {
     if (!first) ret += _(",");
     first = false;
-    // todo: include keys
+    if (index == -1) {
+      ret += key->toCode();
+      ret += _(":");
+    }
     ret += v->toCode();
   }
   ret += _("]");
@@ -454,12 +479,14 @@ class ScriptCustomCollectionIterator : public ScriptIterator {
 public:
   ScriptCustomCollectionIterator(ScriptCustomCollection const* col, ScriptValueP const& col_owned)
     : col(col), col_owned(col_owned), pos(0), it(col->key_value.begin()) {}
-  ScriptValueP next(ScriptValueP* key_out) override {
+  ScriptValueP next(ScriptValueP* key_out, int* index_out) override {
     if (pos < col->value.size()) {
       if (key_out) *key_out = to_script((int)pos);
+      if (index_out) *index_out = (int)pos;
       return col->value.at(pos++);
     } else if (it != col->key_value.end()) {
       if (key_out) *key_out = to_script(it->first);
+      if (index_out) *index_out = -1;
       return (it++)->second;
     } else {
       return ScriptValueP();
@@ -498,14 +525,14 @@ class ScriptConcatCollectionIterator : public ScriptIterator {
 public:
   ScriptConcatCollectionIterator(const ScriptValueP& itA, const ScriptValueP& itB)
     : itA(itA), itB(itB) {}
-  ScriptValueP next(ScriptValueP* key_out) override {
+  ScriptValueP next(ScriptValueP* key_out, int* index_out) override {
     if (itA) {
-      ScriptValueP v = itA->next(key_out);
+      ScriptValueP v = itA->next(key_out, index_out);
       if (v) return v;
       else   itA = ScriptValueP();
     }
     // TODO: somehow fix up the keys
-    return itB->next(key_out);
+    return itB->next(key_out, index_out);
   }
 private:
   ScriptValueP itA, itB;
diff --git a/src/script/value.hpp b/src/script/value.hpp
index 281f9cb5..268896ad 100644
--- a/src/script/value.hpp
+++ b/src/script/value.hpp
@@ -104,8 +104,10 @@ public:
     */
   virtual ScriptValueP makeIterator(const ScriptValueP& thisP = ScriptValueP()) const;
   /// Return the next item for this iterator, or ScriptValueP() if there is no such item
-  /** If key_out != 0, then it will recieve the key of the item */
-  virtual ScriptValueP next(ScriptValueP* key_out = nullptr);
+  /** If key_out != nullptr, then it will receive the key of the item
+   *  If index_out != nullptr, then it will receive to index of the item if it is in an indexable container
+  */
+  virtual ScriptValueP next(ScriptValueP* key_out = nullptr, int* index_out = nullptr);
   /// Return the number of items in this value (assuming it is a collection)
   virtual int itemCount() const;
   /// Get a member at the given index
diff --git a/test/script/script-functions.mse-script b/test/script/script-functions.mse-script
index 9d7287bc..f1602550 100644
--- a/test/script/script-functions.mse-script
+++ b/test/script/script-functions.mse-script
@@ -93,6 +93,7 @@ assert( length([]) == 0)
 assert( length([1]) == 1)
 assert( length([1,2]) == 2)
 assert( length([a:1,b:2]) == 2)
+assert( length([1,2,3] + [4,5]) == 5)
 assert( length("") == 0)
 assert( length("1") == 1)
 assert( length("12") == 2)
@@ -183,7 +184,7 @@ assert(to_code("abc") == "\"abc\"")
 assert(to_code("\\\<\n\r\t") == "\"\\\\\\<\\n\\r\\t\"")
 assert(to_code(1) == "1")
 assert(to_code([1,2,3]) == "[1,2,3]")
-assert(to_code([x:"y"]) == "[x:\"y\"]")
+assert(to_code([x:"y"]) == "[\"x\":\"y\"]")
 
 # count_chosen
 assert( count_chosen("")                                 ==  0 )