Most days I scan the web for relevant or interesting stuff and today I found a real treasure. A website where they have curated a list of C and C++ single file libraries. That is libraries that are not multiple files but mostly one. I say mostly because there are a few with 2 or 3 files.
The bulk are in C++ but there are a large number of C/C++ and quite a number of C. All have their licensing; these are open source but licences vary a bit.
It’s worth a trawl through the List. For instance there’s an interpreter for a BASIC dialect scripting language,