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Geek Culture / Need example of scripting

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zenassem
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Location: Long Island, NY
Posted: 24th Sep 2008 09:22 Edited at: 24th Sep 2008 09:26
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<Meant for this post to under the Dark Basic Pro board.>

QUESTION/Request
So I would be truly appreciative if anyone could give me the equivalent of a "Hello World" example of scripting with DBPro. I don't necessarily need it to be in any particular scripting language, and a simple custom script/parse will also due.

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Why am I asking?
Here's a bit of irony. I understand the reasons for scripting, and the idea behind it; separating game logic from the core engine, making modifiable scenarios, being able to see things in action on the fly, not having to recompile the entire program to make a game logic change, etc...

SO I know it's something I would like to incorporate into my development. BUT....

I just don't understand how to put it into practice. Everything I google just gets to involved in the specifics of a scripting language, or too heavily involved with another language that I just don't seem to get it. Also, I'm not sure how or why scripting is different then me reading data from files into my game (except for the fact that I can't really type "Spawn ("gnome",param,param,param...)" and see it happen.

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Van B
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Posted: 24th Sep 2008 09:26
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Zotoaster has made several examples of scripting, you should check those out first - I think one of them is being featured in this months newsletter, but code snippets should be the place to look.


Health, Ammo, and bacon and eggs!
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zenassem
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Posted: 24th Sep 2008 09:27
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thx Van B, I'll check it out now.

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NeX the Fairly Fast Ferret
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Posted: 24th Sep 2008 11:08
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The way the darkSMASH script parser worked was to first remove spaces, then scan the whole file into a two dimensional array with commands and then up to eight parameters using ( and , and ) to split up commands. It was dead quick.

The best way in which to divide a script up like this is to read it in one byte at a time, storing the bytes until the character the program is looking for is found.

The darkSMASH script system was pretty simplistic although it did have if/endif blocks. Start small. Begin by just making your parser split a list of commands into strings in an array, and then have an interpreter fly through that array.

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Roxas
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Posted: 24th Sep 2008 17:35
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Nex thats really how i did it on my Flare Engine tho later i made compiler for scripts too that compiled script to machine code and was lighting fast lol. I dont remember the site but there was good site to learn scripting and make compiler for scripts etc. Someone posted it to these forums.

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Zotoaster
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Posted: 24th Sep 2008 19:51
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That's the most efficient way really to make any scripting system. Once you understand all the steps required, it's rather simple. You start with the lexer/tokenizer, which as Nex said, should split the script into little "words". The compiler should read those words and make a list of simple instructions, with 0 or a few parameters. I recommend for extra speed you don't store the instructions or parameters as strings though (unless the parameter itself is supposed to be a string), but more like a value representing an instruction. i.e., the instruction "push" might have a value 1, and "print" have a value of 2. You might have an instruction list such as:


... which would of course print "hello world" to the screen.

All it takes then is to interpret the bytecodes one by one to execute the script.


I'm considering writing a tutorial on this, heheh

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NeX the Fairly Fast Ferret
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Posted: 24th Sep 2008 19:59
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The arena scripts for darkSMASH did do that in fact, because code was being interpreted every frame. The commands were converted to a list of bytecode, each of which had a pointer pointing at a memblock with parameters...

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Zotoaster
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Posted: 24th Sep 2008 20:08 Edited at: 24th Sep 2008 20:11
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Quote: " each of which had a pointer pointing at a memblock with parameters"


That's rather clever I think. It depends what you want to do as far as compiling though. Sometimes you might want somewhat game-specific scriping systems, in which case you could use a SIMD (single instruction multiple data) instruction list, as you did. I tend to try and make mine rather flexible, so mine don't require many parameters (never found myself using more than two), so for that reason I just have a UDT to store instructions with their parameters, such as:


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