I really liked the Go standard library (or at least from around 1.4-ish, it might have gotten more complicated now). I liked that it was actually possible to r

I really liked the Go standard library (or at least from around 1.4-ish, it might have gotten more complicated now). I liked that it was actually possible to read it and understand what was going on. In a similar vein, P. J. Plauger's version of the The Standard C Library is nice because even if it might not be especially optimized(?), you can actually read the code and understand the concepts that the standard library is based on. Software Tools by Kernighan and Plauger would also be great except that you have to translate from the RatFor dialect of Fortran or Pascal to use the code examples. Even so, I used its implementation of Ed, to create a partial clone in PowerShell that let me do remote file editing on Windows via Powershell when that was the only access that was available. So even over 4 decades and various operating systems removed, there are still concepts in there that are useful. Jonesforth is also a great and mind blowing code base although I'm not sure where the canonical repository is currently.