add "split" into standard library

Subject: add &quot;split&quot; into standard library
From: Hugo &lt;tkokof@ ... &gt;
Date: Sat, 1 Jun 2019 11:24:24 +0800 (CST)

Hi, everyone

Lua standard library do not provide "split" function, and there are a lot of implementations with different limitations, there is even a wiki about this topic(http://lua-users.org/wiki/SplitJoin).

I've wonder since a "join"(table.join) function is there, then why isn't a "split" function ?

After some searchings, I've found a related(and old) answer from Roberto : http://lua-users.org/lists/lua-l/2002-11/msg00157.html.

Seems the reason is just because trivial performance gain ?

I'm curious about more details (in my case(maybe not in common), "split" is commonly used and should be defined well).

And there is also a common(and big) question here : What is the basis of deciding which function should be added into standard library and which should not ?

tkokof1