Vis
A vi-like editor based on Plan 9's structural regular expressions
... be conveniently expressed using Lua in the form of LPG. The editor core is written in a reasonable amount of clean (your mileage may vary), modern and legacy-free C code, enabling it to run in resource-constrained environments. The implementation should be easy to hack on and encourage experimentation. There is also a Lua API for in-process extensions. Vis strives to be simple and focuses on its core task: efficient text management.