Re: [ANN] Lua 5.2.1 (work1) now available

[Rebel Neurofog <rebelneurofog@...>]

> Lua 5.2.1 (work1) is now available at
>        http://www.lua.org/work/lua-5.2.1-work1.tar.gz

First, the are some disadvantages I suppose:
1. No more simple pointer comparison in C to test string equality.
Following example shows why:
#include "lua.h"
#include "lauxlib.h"
#include <stdio.h>

int main ()
{
    lua_State *L = luaL_newstate ();
    char big_string[1024];
    memset (big_string, 'c', 1023);
    big_string[1023] = '\0';
    int i;
    for (i = 0; i < 10; i++)
        fprintf (stderr, "%p - this is supposed to be the same\n",
lua_pushstring (L, big_string));
    return 0;
}

Simple pointer comparison is needed for fast string constant to C enum
resolving.
This is very fast trick when string is pushed into Lua registry and
returned pointer
is saved into binary key matching structure created right after lua_newstate ().
Pointer to that key matching structure is resolved after getting
allocator user data
with lua_getallocf (). I may write such library if someone is
interested (I'm planning
to implement the method in my project but didn't get to this yet).
2. Such change may break reliance on fast comparisons of huge string
(say check for buffer equality in text editor). So this may hardly modify
optimization approaches by shifting bottle necks significantly.

Here's my vision:
1. Lua strings are currently perfect and should not be changed.
Experienced Lua programmers have detailed understanding where and how
(e. g., "table.concat ()")
Lua strings should be used and where shouldn't.
2. Situations with byte arrays (especially mutable) are usually worked out by
creating project-specific user-data based modules to work with.
Here's my way for example:
http://devel.nomrhis.net/Client_API_reference/modules/bytea
Of course it's not designed for mainstream Lua.
4. I think there should be standard common mainstream Lua module
(and also sandbox-safe as 'string', 'math' and 'table') for processing
mutable byte array
with fixed length given at creation time.
5. It is probably possible to implement reallocation of data block
given by lua_newuserdata ().
Although it may give problems with multithreaded Lua...

Conclusion:
Lua strings have significant advantages which shouldn't be broken by
intension to create
absolute universal data type for all things.
Instead standard mutable byte array should be implemented on top of user data.