diff --git a/doomsday/libs/core/include/de/data/string.h b/doomsday/libs/core/include/de/data/string.h
index faf1ad743a..bb0db01f9f 100644
--- a/doomsday/libs/core/include/de/data/string.h
+++ b/doomsday/libs/core/include/de/data/string.h
@@ -443,7 +443,7 @@ class DENG2_PUBLIC String : public QString
     static void advanceFormat(String::const_iterator &i,
                               String::const_iterator const &end);
 
-    static String join(QList<String> const &stringList, String const &sep = String());
+    static String join(QList<String> const &stringList, String const &sep = {});
 };
 
 /**
diff --git a/doomsday/libs/core/include/de/libcore.h b/doomsday/libs/core/include/de/libcore.h
index 8bc570366a..7945067fa8 100644
--- a/doomsday/libs/core/include/de/libcore.h
+++ b/doomsday/libs/core/include/de/libcore.h
@@ -650,6 +650,17 @@ inline OutContainer map(const InContainer &input, Func func) {
     return out;
 }
 
+template <typename OutContainer, typename InContainer>
+inline OutContainer map(const InContainer &input,
+                         std::function<typename OutContainer::value_type (
+                             typename InContainer::value_type const &)> func) {
+    OutContainer out;
+    for (auto i = input.begin(); i != input.end(); ++i) {
+        out.push_back(func(*i));
+    }
+    return out;
+}
+
 template <typename ContainerType>
 inline ContainerType filter(ContainerType const &c,
                             std::function<bool (typename ContainerType::value_type const &)> func) {
diff --git a/doomsday/libs/core/src/data/string.cpp b/doomsday/libs/core/src/data/string.cpp
index f25bdc2bc3..403dd20c53 100644
--- a/doomsday/libs/core/src/data/string.cpp
+++ b/doomsday/libs/core/src/data/string.cpp
@@ -609,9 +609,9 @@ void String::advanceFormat(String::const_iterator &i, String::const_iterator con
     }
 }
 
-String String::join(QList<String> const &stringList, String const &sep)
+String String::join(StringList const &stringList, String const &sep)
 {
-    if (stringList.isEmpty()) return "";
+    if (stringList.isEmpty()) return {};
 
     String joined;
     QTextStream os(&joined);