Table constructions in Lua are expensive, creating and destroying thousands of "vector" tables frame to frame in an engine can cause serious performance problems when Lua's GC is triggered; this is a vector library that attempts to solve this problem by interning construction and reusing references
It's not safe to modify a vector that may be referenced multiple times
so this library also implements reasonably efficent read-only data types
through the use of __index metamethods.
construction cost in the uncached case is ~2x more expensive but the same in the cached case, the real winnings comes from not having a destruction phase ever occur, e.g seeing 60% of GC frame to frame occur because of one-off vector constructions go away is quite significant, vector comparisons are ~20x faster since it's just object identity, i.e pointer comparison in the VM.
performance is made up by interning so if you're not careful you can
run out of memory rather quickly, make smart decisions when to call
clear_cache() on each of the vector caches.