The Genesis of Mix: Early Days of Self-Applicable Partial Evaluation (Invited Contribution)

Forty years ago development started on Mix, a partial evaluator designed specifically for the purpose of self-application. The effort, led by Neil D. Jones at the University of Copenhagen, eventually demonstrated that non-trivial compilers could be generated automatically by applying a partial evaluator to itself. The possibility, in theory, of such self-application had been known for more than a decade, but remained unrealized by the start of 1984. We describe the genesis of Mix, including the research environment, the challenges, and the main insights that led to success. We emphasize the critical role played by program annotation as a pre-processing step, later automated in the form of binding-time analysis.