Buteau, Sacristin and Muller's target article raises the pertinent issue of how to describe a sustained undergraduate course on computational thinking and programming for mathematical learning. There is so little work on this issue that it is worthwhile to reflect on this study and to raise questions regarding the options and tools available or needed to understand sustained constructionist activity. Here, I focus on questions regarding how to understand the instructor's craft knowledge in practice and what constructionist mathematical learning may look like when programming is at the service of engagement with mathematical concepts.