Lua Five Features

 As several people have suggested, the next version will be 5.0. We are
 still planning to realease it (at least an alpha version) by May, but we
 are not sure we will be able to do that. Anyway, we are trying to fix
 some decisions. So, following is a list of the main differences from
 lua4.1w4 to Lua 5.0. Most of them have been discussed in the list
 already.
 
 - "generic for": will have an implicit state, so that for several common
 uses you don't need a new closure for each `for'.
 
 - co-routines: basically as it is, but we will try to allow for `yield's
 inside linehooks.
 
 - metatables: as it is now, but the keys will be prefixed with '__'
 (e.g. __gettable, __settable, etc.) The main idea is to facilitate
 finding parts of the code that deal with metatables.
 
 - error handling: we will probably change functions related to error
 handling (dostring/dofile, call, etc.). We will have a proposal soon.
 
 - standard libraries: standard libraries now use "namespaces". So,
 strfind now is str.find, sin is math.sin, fileopen is io.open. Some
 basic functions (type, assert, error, etc.) are still global. We also
 changed the io library; e.g. files act as objects (f = io.open(...);
 f:read(...); f:write(...)).
 
 - declaration of globals: we introduced global declarations:
 
     global a,b,c
     global a,b,c in T
     global in T        -- change the default
 
 So, "global in nil" forces declarations for every variable;
 "global in {}" puts all undeclared variables into a private table;
 "global sin, cos in math" allows the unqualified use of the
 names "sin" and "cos".
 
 - we introduced a "lightweight userdata", which is a value and not an
 object.
 
 - require: the path now specifies "templates", instead of directories.
 For instance, require "A" with path "./?.lua;./?.lc;/usr/local/?/init.lua" 
 will look for "./A.lua", "./A.lc", and "/usr/local/A/init.lua".
 
 
 What is still missing?
 
 - "partial orders": the bug in comparisons with NaN must be solved. That
 implies in not reducing other comparisons to "lt", and so probably the
 solution will also change the "lt" tag method.
 
 - the declaration "global in nil" forces the declaration of *all* names.
 So, even basic functions like "type" and "error" should be declared. It
 would be good to have some scheme to "pre-declare" some identifiers...
 
 -- Roberto