Command system?

[Longor]

Hi!

I wanted to ask what kind of command system (parsing/processing) Vintage Story is using, and what it can do/what its restrictions are.

[Tyron]

Heya! If you are asking from a minecraft-style-command-system standpoint:

There's currently no commands available that would let you interact (setblock/testfor/etc styled) with the world and there's no command block. What we do have is:

• A lot of commands to help you administer the server and player privileges as well as commands useful during development
• A macro manager on the Client that let's you execute several commands at once using a keyboard shortcut. So you can e.g. map /time set day to CTRL+D - The idea is borrowed from World of Warcrafts Macro System, thats kind of the direction i want to go with this - as ways to automate your character (/equip, /say, /spell, /use, etc.)
• Server mods can freely register new commands and handle their response

I'm also undecided if a minecraft-style command system is something I should implement - the whole idea of it feels like an excuse for not having a mod api which Vintagestory has however. Conceptually it is also kinda ambiguous. I would rather go for either fully programmable blocks through Lua code or have let such commands be the actual blocks (teleport block, testfor block, setblock block, etc.). 

[Longor]

Well if that is the case, I would like to recommend something:

Use a custom LISP dialect for commands; that gives you a ton of power, versatility and possibilities, while still keeping the commands simple which is, in my personal opinion, the best thing about commands: You don't need to learn a entire scripting language for them, only bits and pieces and a brutally simple syntax.

Using something like a custom LISP dialect here makes things more streamlined, so the parsing of commands is never really ambiguous. This in turn can make auto-completion simpler, since you have a unified form of how commands are structured. Also, the syntax of LISP actually looks like the command syntax you can find everywhere, so there's no need to change your habits.

A simple dialect could be (here as EBNF):

command ::= EXPRESSION

EXPRESSION ::= OPERATOR (WORD | STRING | NUMBER | JSON | ENTITYSELECTOR | BLOCKSELECTOR | SUBEXPRESSION)

OPERATOR   ::= WORD
WORD       ::= ?Any sequence of characters, terminated by whitespace?
STRING     ::= '"' (?Sequence of characters without '"'?) '"'
NUMBER     ::= ?Insert Grammar for Numbers here?
JSON       ::= ?Insert Grammar for JSON Object here?

ENTITYSELECTOR ::= '@' SUBEXPRESSION
BLOCKSELECTOR  ::= '#' POSCOMP POSCOMP POSCOMP
POSCOMP        ::= (SUBEXPRESSION | ['~'] NUMBER)
SUBEXPRESSION  ::= '(' EXPRESSION ')'

I just wrote that grammar up, so don't throw that blindly into a parser generator!

Oh and before I forget: Vintage Story looks darn beautiful for being in the alpha stage

[Tyron]

Oh wow, haven't seen an EBNF for a few years now

If we go that far, wouldn't it make sense to just go all the way and use lua/c# expressions as commands? i.e. /command SetBlock("water", GetPlayerPosition(FindNearestPlayer()));
Thats more powerful, still pretty simple syntax and perhaps even less effort than implementing a custom parser.

 

14 minutes ago, Longor said:

Oh and before I forget: Vintage Story looks darn beautiful for being in the alpha stage

The magic of shaders and consistency  Thanks!

[Longor]

Well... lets compare the command you provided:

SetBlock("water", GetPlayerPosition(FindNearestPlayer()));

With a LISP-style variant (entity selector syntax just invented):

setblock @(type: "player", count: 1) "water"

Which one is simpler, and which one is faster to type, taking into account that you would have basic understandings of both variants?

[Tyron]

To be quite honest, the C# variant is simpler to read and understand. It immediately gives you an understanding what it does. With your lisp syntax command its not immediately clear what it does. I can also make the C# variant faster to type at the cost of intuitivness: setBlock("water", PlrPos(NearestPlr()))

I don't really see the gain of a LISP Syntax here

[Longor]

If you cant see any gains with a lisp syntax, then go ahead and use C#/Lua. Its your engine after all! 

One gain the lisp syntax has is that autocompletion is simpler to implement, since its just lists of data elements.