Co-evolution as the key for live programming

The promise of live programming is to shorten or even break the infamous edit-compile-run cycle, providing live feedback on a program's envisioned behavior while it is being written. Several live programming languages and environments exist, from venerable examples (Smalltalk, LISP) to more recent efforts like Ruby. In most cases either the IDE comes as an afterthought, after the language is designed, or novel languages are made to fit into existing IDEs. We pursue a middle ground by co-evolving both a language and its IDE: we are developing a novel live programming language, called Moon, from scratch, and are concurrently building its IDE. We illustrate our efforts so far and discuss our overall vision.