But a lot of the time it wasn't really about programming as such—it was about, what is the idea? What are we trying to do with this dataflow analysis, anyway? You try to say in a clear way what this step of the program is meant to do. So we spent quite a lot of time just being clear on what the inputs and the outputs are and working on the data types of the inputs and the outputs. Just getting the data types right, already you've said quite a lot about what your program does. A surprisingly large amount, in fact.