do we really need a visualizer?IMO, the question about “visualization” might be rhetorical - visualization of what? Debugging belongs to the realm of creativity, not of clockwork engineering. Debugging is iteration. Debugging is notation-specific. Debugging is paradigm-specific. For example, if you Design a system using, say, the OO paradigm, you want a debugger that shows you the OO-iness of your code, not, say, machine-level single-stepping from a completely different paradigm. @Kartik Agaram’s Handmade-network video reminds me of a long-standing je ne sais quoi I’ve had about GVL . Kind of a projectional editing REPL (based on simplistic-SVG?).
, which has various affordances for tinkering with what's happening in the running program. I've written a couple of interactive interpreter/emulator systems for small architectures to make it easier to live code embedded systems. (When I taught Operating Systems at uni, I'd always have the students deal with the pain of working directly with the slow hardware before introducing cross-compilation, then emulation, on faster hardware to help them develop an intuition for when to make those decisions in real life.)