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This article introduces the relevant knowledge of "how to use the Lua function in CAccord +". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

1. Brief introduction

This time we mainly talk about how to define functions by Lua and then call them in C or C++. Here we will not deal with the object problem of C++, but only discuss the parameters of the calling function, return values and the use of global variables.

two。

Here, we first define a simple add () in e12.lua. XPerry y is the two parameters of the addition, and return returns the added result directly.

Example e12.lua

-- add two numbers function add (x, y) return x + y end

In the previous time, we said that lua_dofile () can execute the lua file directly in C. Because there is only one add () function defined in this program, the result is not direct after the program is executed, and the effect is the same as defining a function in C.

Lua functions can have multiple arguments or return values, all of which are implemented by stack. When you need to call a function, push the function onto the stack, then press all the parameters sequentially, and then call the function with lua_call (). After the function returns, the return value is also stored in the stack. This procedure is the same as assembling the process of performing function calls.

Example e13.cpp is an example of calling the Lua function above

# include extern "C" {/ / this is a C++ program, so extern "C", / / because the header files of lua are all # include "lua.h" # include "lualib.h" # include "lauxlib.h"} / * the Lua interpreter * / lua_State* L; int luaadd (int x, int y) {int sum; / * the function name * / lua_getglobal (L, "add") / * the first argument * / lua_pushnumber (L, x); / * the second argument * / lua_pushnumber (L, y); / * call the function with 2 arguments, return 1 result * / lua_call (L, 2, 1); / * get the result * / sum = (int) lua_tonumber (L,-1); lua_pop (L, 1); return sum;} int main (int argc, char * argv []) {int sum; / * initialize Lua * / L = lua_open () / * load Lua base libraries * / lua_baselibopen (L); / * load the script * / lua_dofile (L, "e12.lua"); / * call the add function * / sum = luaadd (10,15); / * print the result * / printf ("The sum is% d\ n", sum); / * cleanup Lua * / lua_close (L); return 0;}

Program description:

We talked about the process of main last time, so this time we will only talk about the process of luaadd.

* first stack the add function with lua_getglobal ()

* then use lua_pushnumber () to stack XBI y in turn.

* then call lua_call () and tell the programs that there are two parameters and a return value

* then we retrieve the return value from the top of the stack and use lua_tonumber ()

* We use lua_pop () to clear the return value

Running result:

The sum is 25

Compiling method

Save the program as e13.cpp under Linux

Gmail + e13.cpp-llua-llualib-o E13

. / e13

Compiling method under VC

* create an empty Win32 Console Application Project first

* add e13.cpp to the project

* Click project setting, and then set the link option, plus two additional libraries of lua.lib lualib.lib

3. Global variable

We used lua_getglobal () above, but we didn't go into detail. Here we give two small examples of global variables.

The function of lua_getglobal () is to push the values of global variables in lua onto the stack.

Lua_getglobal (L, "z")

Z = (int) lua_tonumber (L, 1)

Lua_pop (L, 1)

Suppose a global variable z is defined in the Lua program, and this Mini Program takes the value of z out and puts it into the variable z of C.

In addition, there is a corresponding function lua_setglobal () in Lua, which populates the specified global variable with the value at the top of the stack.

Lua_pushnumber (L, 10)

Lua_setglobal (L, "z")

For example, in this Mini Program section, the global variable z in lua is set to 10. If z is not defined in lua, a

The global variable z is also set to 10.

This is the end of the introduction of "how to use the Lua function in CAccord Category +". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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