Diff Tool Knows What You Mean

Jul 27, 2023

We will admit to not being particularly artistic, but we do remember an art teacher telling us that sometimes it is better to draw what isn't there instead of what's there — a concept known as negative space. [Wilfred] makes a similar point when explaining his "fantastic diff" tool called, appropriately, difftastic. He points out that when comparing two programs, the goal isn't so much to determine what changed, but rather what stayed the same. The more you can identify as the same, the less you have to show as a change.

The tool compares source code in a smart way, assisted by tree-sitter which has many different languages already parsed, at least well enough for this purpose. According to [Wilfred's] post the tool supports 44 different languages ranging from bash and YAML, Verilog to VHDL, and C++ to Rust, among others.

Of course, the tool by itself is worth taking note of. But the real gems in the write-up are things like tree-sitter and a lucid description of the algorithm (borrowed from autochrome) for working out the minimal set of changes.

The code is still under development and the output is not always as clear as he would like. Still, a pretty good tool and a great write-up on the development challenges.

Although Verilog and VHDL are a start, we really want diff for schematics. Oh, and PCB layouts, don't forget those,e either.