Re: [PROPOSAL] a new function: table.proto()

[steve donovan <steve.j.donovan@...>]

On Tue, May 4, 2010 at 1:00 PM, Paul Hudson <phudson@pobox.com> wrote:
> examples. Is improving this step actually something that would make a
> noticeable difference?

Well, let's expose lua_creatable:

[[
// xtable.c
#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>

static int l_createtable (lua_State *L) {
  int narr = luaL_optint(L,1,0);         // initial array slots, default 0
  int nrec = luaL_optint(L,2,0);   // intial array of hash slots, default 0
  lua_createtable(L,narr,nrec);
  return 1;
}

static const luaL_reg xtable[] = {
    {"create",l_createtable},
    {NULL,NULL}
};

LUALIB_API int luaopen_xtable(lua_State *L)
{
    luaL_register (L, "xtable", xtable);
    return 1;
}
]]

The resulting test:
[[
require 'xtable'
local create = xtable.create

for i = 1, 10000000 do
    local t = create(0,5)  -- 5 hash slots
    t.a = i; t.b = i; t.c = i; t.d = i; t.e = i
end
]]

takes 8.9 sec

whereas

[[
for i = 1, 10000000 do
    local t = {}
    t.a = i; t.b = i; t.c = i; t.d = i; t.e = i
end
]]

takes 18.2 sec

Whether this would actually make a serious difference in a real
application, I don't know.

But the point is that we don't need to add to the public API to get
this functionality exposed.

steve d,