Re: Self-awareness of functions?
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- Subject: Re: Self-awareness of functions?
- From: Luis Carvalho <lexcarvalho@...>
- Date: 2010年12月30日 11:57:12 -0500
Dirk Laurie wrote:
<snip>
> Trouble is, I can't see a way to write a C function "self" that
> can be imported into the global namespace and would achieve this.
> "self" would have to be an implicitly defined local variable
> referring to the function under construction, created by the Lua
> compiler: in effect, a reserved word.
<snip>
I missed the "C" part. Here's one solution, just for completeness:
/* self.c */
#include <lua.h>
static int self (lua_State *L) {
int n = lua_gettop(L);
lua_Debug ar;
lua_getstack(L, 1, &ar); /* function calling `self' */
lua_getinfo(L, "f", &ar); /* push function */
lua_insert(L, -(n+1));
lua_call(L, n, LUA_MULTRET);
return lua_gettop(L);
}
int luaopen_self (lua_State *L) {
lua_pushcfunction(L, self);
return 1;
}
Test:
Lua 5.1.4 Copyright (C) 1994-2008 Lua.org, PUC-Rio
> self = require"self" -- fine as long as you don't use ":"
> f = function(n) if n<2 then return 1 end return n*self(n-1) end
> print(f(5))
120
> fib = function(n) if n<3 then return n-1 end return self(n-1) +
self(n-2) end
> print(fib(10))
34
Another option is a getter:
static int getself (lua_State *L) {
lua_Debug ar;
lua_getstack(L, 1, &ar); /* function calling `self' */
lua_getinfo(L, "f", &ar); /* push function */
return 1;
}
Cheers,
Luis
--
Computers are useless. They can only give you answers.
-- Pablo Picasso
--
Luis Carvalho (Kozure)
lua -e 'print((("lexcarvalho@NO.gmail.SPAM.com"):gsub("(%u+%.)","")))'