Advent of Code 2019 solutions in Ruby.
Advent of Code puzzles are usually standalone, but this year half of them built on an "Intcode" virtual machine. The Intcode "language" (if you will) is defined, and the VM is incrementally constructed, over puzzles 2, 5, and 9. Our final implementation, in which the VM is a function that yields to an associated block for I/O, was developed in puzzle 11 and reused thereafter.