Several recent projects attempt to blur the line between static and dynamic typing by adding optional type declarations to scripting languages. These declarations support a strategy of gradual typing, in which programmers initially write in a traditional scripting style and then add declarations incrementally to increase reliability or decrease run-time cost. Learn about the Dart, Hack, and TypeScript languages, promoted by Google, Facebook, and Microsoft, respectively. What are your impressions? How easy do you think it will be in practice to retrofit declarations into programs originally developed without them?