Running a LUA script one part at a time

Engines and Middleware Programming

Started by lawnjelly December 03, 2012 08:07 PM

2 comments, last by Endurion 11 years, 4 months ago

2,021

Author

December 03, 2012 08:07 PM

Hiya, I have some experience writing my own scripting languages in the past, but wanted to have a go at using LUA for a little 2d rpg type game.

It was very easy to get it loading a script and running it within the game, so far so good.

Next stage is, instead of running an entire script at once (via lua_pcall), I want to be able to run through a script, up until it reaches certain time consuming functions, when I want to pause the script until the c++ tells it to resume again.

Here's the flow:

monster.lua:



TextOut("Hello I am a monster")

Wait(5)

TextOut("Now I'm going to eat you")

Wait(2)

MoveToPlayer()

TextOut("Yum yum")

So within most scripts run by characters etc, I need to pause the script, get on with running the rest of the game, other scripts etc, then resume again when the wait condition is satisfied.

The example above has 2 'waiting' functions, Wait (number of seconds), and MoveToPlayer (which may take a varying amount of time).

Hopefully this should make sense.

Does anyone have any idea how I should achieve this in lua? I'm having inkling feelings it may be to do with the yield and resume commands, but I haven't seen any decent explanations.

Many thanks.

wqking

778

December 04, 2012 04:00 AM

Pseudo code, you must polish it...



Lua code

function taskA()

    TextOut("Hello I am a monster")

    Wait("A", 5)

    TextOut("Now I'm going to eat you")

    Wait("A", 2)

    MoveToPlayer()

    TextOut("Yum yum")

end

function Wait(what, period)

    CppWait(what, period)

    coroutine.yield()

end

function resumeA()

    coroutine.resume(coA)

end

-- main code

coA = coroutine.create(taskA)



C++ code

void CppWait(std::string what, int period)

{

    // add period to some condition list by "what"

}

void YourGameLoop()

{

    if(condition for taskA is met) {

	    callLuaCode(resumeA);

    }

}

Hope the code explains itself.
Note: I never used Lua coroutine before...

https://www.kbasm.com -- My personal website

https://github.com/wqking/eventpp eventpp -- C++ library for event dispatcher and callback list

https://github.com/cpgf/cpgf cpgf library -- free C++ open source library for reflection, serialization, script binding, callbacks, and meta data for OpenGL Box2D, SFML and Irrlicht.

lawnjelly

2,021

Author

December 04, 2012 09:16 AM

Ahha!

Thanks wqking, that seems to make a lot more sense.

I thought it should be able to do it, just wasn't sure of the syntax. Surprising that I couldn't find more tutorials on this, as it's such a basic necessity for scripting in a game. But maybe I just didn't know what to google for before.

Endurion

5,545

December 04, 2012 05:04 PM

Also a hint: You can return a value to C via yield and pass a parameter in via resume. This may come in handy for the Wait function.

Fruny: Ftagn! Ia! Ia! std::time_put_byname! Mglui naflftagn std::codecvt eY'ha-nthlei!,char,mbstate_t>

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