人人都愛奴兒
Stack
Manipulation(Offical API reforence 3.3 Stack Manipulation)
The API o?ers the following functions for basic stack manipulation:
void lua_settop (lua_State *L, int index);
void lua_pushvalue (lua_State *L, int index);
void lua_remove (lua_State *L, int index);
void lua_insert (lua_State *L, int index);
void lua_replace (lua_State *L, int index);
As an example, if the stack starts as 10 20 30 40 50* (from bottom to top; the ‘*’ marks the top), then
lua_pushvalue(L, 3) --> 10 20 30 40 50 30*
lua_pushvalue(L, -1) --> 10 20 30 40 50 30 30*
lua_remove(L, -3) --> 10 20 30 40 30 30*
lua_remove(L, 6) --> 10 20 30 40 30*
lua_insert(L, 1) --> 30 10 20 30 40*
lua_insert(L, -1) --> 30 10 20 30 40* (no effect)
lua_replace(L, 2) --> 30 40 20 30*
lua_settop(L, -3) --> 30 40*
lua_settop(L, 6) --> 30 40 nil nil nil nil*
在lua.h中有macro：
#define lua_pop(L,n) lua_settop(L, -(n)-1)
則
pop(n)==settop(-n-1)
settop(n)==pop(-n-1) == push(n)
曰:出棧幾個元素，相當于將這個數字加一，然后用和的相反數作為棧頂;從棧頂往下數了幾個數標記為棧頂，則將這個數加一，然后用這個和數出棧。好比公司要擴招了，就招n個伢，那就將n個伢入棧，工號一個個的加，加n次。或者要裁員了，就裁m個伢，則按順序將工號最大的前面m個伢遣散了，老員工暫時不動，公司裁員后的最大的工號嘛就將裁員人數加一后，往下數這個數，數到哪個，哪個就是工號最大的伢了。
Querying(Offical lua api reference 3.4 Querying the Stack)
To check the type of a stack element, the following functions are available:
int lua_type (lua_State *L, int index);
int lua_isnil (lua_State *L, int index);
int lua_isboolean (lua_State *L, int index);
int lua_isnumber (lua_State *L, int index);
int lua_isstring (lua_State *L, int index);
int lua_istable (lua_State *L, int index);
int lua_isfunction (lua_State *L, int index);
int lua_iscfunction (lua_State *L, int index);
int lua_isuserdata (lua_State *L, int index);
int lua_islightuserdata (lua_State *L, int index);
The API also contains functions to compare two values in the stack:
int lua_equal (lua_State *L, int index1, int index2);
int lua_rawequal (lua_State *L, int index1, int index2);
int lua_lessthan (lua_State *L, int index1, int index2);
曰:黃帝生眾人，眾人生萬物，萬物生八卦，八卦生努爾盞，lua棧就是眾生能觸摸到的祖先的氣。你可以在奴兒盞里隨心所欲的玩，逾矩的玩，窺視那些終生像:忠奸善惡，數串表函，是不是三聚氰胺防腐劑，是不是裸官醉駕二次碾壓.
取棧值(offical api 3.5 Getting Values from the Stack)
To translate a value in the stack to a speci?c C type, you can use the following conversion functions:
int lua_toboolean (lua_State *L, int index);
lua_Number lua_tonumber (lua_State *L, int index);
const char *lua_tostring (lua_State *L, int index);
size_t lua_strlen (lua_State *L, int index);
lua_CFunction lua_tocfunction (lua_State *L, int index);
void *lua_touserdata (lua_State *L, int index);
lua_State *lua_tothread (lua_State *L, int index);
void *lua_topointer (lua_State *L, int index);
曰:可以將盞里的東西讀出來:數、串、真、假、函、線、針。不管盞里放的是神馬五谷雜糧，都可以讀出來啦。
存棧(offical api reference 3.6 Pushing Values onto the Stack)
The API has the following functions to push C values onto the stack:
void lua_pushboolean (lua_State *L, int b);
void lua_pushnumber (lua_State *L, lua_Number n);
void lua_pushlstring (lua_State *L, const char *s, size_t len);
void lua_pushstring (lua_State *L, const char *s);
void lua_pushnil (lua_State *L);
void lua_pushcfunction (lua_State *L, lua_CFunction f);
void lua_pushlightuserdata (lua_State *L, void *p);
曰:五谷雜糧都可以往盞里裝。最好是五年藏梅花上的雪，夏日收在盞里。
棧指針(offical api reference 3.2 The Stack and Indices)
A positive index represents an absolute stack position (starting at 1);
a negative index represents an o?set from the top of the stack.
We say that an index is valid if it lies between 1 and the stack top (that is, if 1 <= abs(index) <= top).
At any time, you can get the index of the top element by calling lua_gettop:
int lua_gettop (lua_State *L);
grows the stack size to top + extra elements:
int lua_checkstack (lua_State *L, int extra);
Whenever Lua calls C, it ensures that at least LUA_MINSTACK stack positions are available.LUA_MINSTACK is de?ned in lua.h
as 20
More formally, we de?ne an acceptable index as follows:
(index < 0 && abs(index) <= top) || (index > 0 && index <= stackspace)
Note that 0 is never an acceptable index
曰:
取棧中頂元指針的值，這個值既指明了棧中頂元的指針，也同時等于棧元的總數。
你有責任使用有效的棧針，不要隨便拿個針就到處戳。
可以增加棧，但不能收縮棧。
0針是不能被接受的，不要用0針到處戳。