Languages as first-class citizens (vision paper)

In this paper, we introduce languages as first-class citizens as a sub-paradigm of language-oriented programming. In this approach, language definitions are in the context of a general purpose programming language with the same status as any other expression. In particular, language definitions are elevated to be run-time values, that can be assigned to variables, passed to functions, returned by functions, and inserted into lists, to name a few possibilities. This approach offers flexible features in the run-time creation and modification of languages, and may promote new idioms in language-oriented programming. As a proof of concept, we have designed and implemented lang-n-play, a functional language with languages as first-class citizens. We present the features of lang-n-play with an example, and show that they naturally enable dynamic programming scenarios.