* Changes from version 4.0 to 5.0
-------------------------------
Language:
+ lexical scoping.
+ Lua coroutines.
+ standard libraries now packaged in tables.
+ tags replaced by metatables and tag methods replaced by metamethods,
stored in metatables.
+ proper tail calls.
+ each function can have its own global table, which can be shared.
+ new __newindex metamethod, called when we insert a new key into a table.
+ new block comments: --[[ ... ]].
+ new generic for.
+ new weak tables.
+ new boolean type.
+ new syntax "local function".
+ (f()) returns the first value returned by f.
+ {f()} fills a table with all values returned by f.
+ \n ignored in [[\n .
+ fixed and-or priorities.
+ more general syntax for function definition (e.g. function a.x.y:f()...end).
+ more general syntax for function calls (e.g. (print or write)(9)).
+ new functions (time/date, tmpfile, unpack, require, load*, etc.).
API:
+ chunks are loaded by using lua_load; new luaL_loadfile and luaL_loadbuffer.
+ introduced lightweight userdata, a simple "void*" without a metatable.
+ new error handling protocol: the core no longer prints error messages;
all errors are reported to the caller on the stack.
+ new lua_atpanic for host cleanup.
+ new, signal-safe, hook scheme.
Implementation:
+ new license: MIT.
+ new, faster, register-based virtual machine.
+ support for external multithreading and coroutines.
+ new and consistent error message format.
+ the core no longer needs "stdio.h" for anything (except for a single
use of sprintf to convert numbers to strings).
+ lua.c now runs the environment variable LUA_INIT, if present. It can
be "@filename", to run a file, or the chunk itself.
+ support for user extensions in lua.c.
sample implementation given for command line editing.
+ new dynamic loading library, active by default on several platforms.
+ safe garbage-collector metamethods.
+ precompiled bytecodes checked for integrity (secure binary dostring).
+ strings are fully aligned.
+ position capture in string.find.
+ read('*l') can read lines with embedded zeros.
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