To derive a program for a given specification R means to find an artifact P that satisfies two conditions: P is executable in some programming language; and P is correct with respect to R. Refinement-based program derivation achieves this goal in a stepwise manner by enhancing executability while preserving correctness until we achieve complete executability. In this paper. we argue t... https://foldlyers.shop/product-category/baritone-ukulele/