Structured Program Generation Techniques

So, you can write a program that generates other programs. Sorry, . . . not impressed. You want to impress me? Make sure your program-generating program only produces well-formed programs. What is “well-formed”, you ask? Well, let’s start with “it parses”. Then let’s get to “. . . and type-checks”. You want to really impress me? Give me an expressive language for program generators in which any program you write will only generate well-formed programs. In this briefing, we will sample the state-of-the-art in program generation relative to the above important goal. If we want to establish program generation as a general-purpose, disciplined methodology, instead of an ad hoc hack, we should be able to check the generator once and immediately validate the well-formedness of anything it might generate. This is a modular safety property for meta-programs, much akin to static typing for regular programs. Some of the emphasis will be on our own work on “class morphing” (or just “morphing”): the statically-safe adaptation of the contents of a class, depending on other classes supplied as parameters. Along the way, lots of other techniques will be discussed and contrasted, from different template facilities, to syntactically-safe program generation, to program staging techniques.