[1.8][Java?] Loading function (math) from string.

[Ernio]

I am looking for either lib or idea how to.

 

I want to have formula for parameters like MaxHealth or other stats like Critical% be saved inside config.

I've alredy everything done to manipulate anything I want, now I need formula.

Simplified example:

Map<String, Integer> attributes; // map holding attributes of entity
//let's say there are those keys/values inside that map:
S, 100
A, 44
K, 90

public int getValueOf(Key key)
{
// Here I want to get formula loaded by config that for this "key"will be for example: "(S+A)*K" and I want this method to return right value.
}

 

Now - I am not stupid - it's very easy to write something like that using shitload of if-s and whatever else, but that all would operate on Strings and have significantly longer computation time than normal "return (S+A)*K" coded in Java.

 

I guess my question is - does anyone know a tool (if that is even possible) that would allow me to create (on config load) virtual method computing my value and give me near-JVM-standard computing time?

 

I hope it's clear what I am looking for.

[Draco18s]

https://www.google.com/#safe=off&q=how+to+write+a+compiler+for+a+trivial+language

[ItsAMysteriousYT]

You will have to write a Parser. Basicly a bunch of well suited if, while and for loops in which you check the function for errors and if there aren't any, then do the solving.

[Ernio]

You will have to write a Parser. Basicly a bunch of well suited if, while and for loops in which you check the function for errors and if there aren't any, then do the solving.

Now - I am not stupid - it's very easy to write something like that using shitload of if-s and whatever else, but that all would operate on Strings and have significantly longer computation time than normal "return (S+A)*K" coded in Java.

Parsing is goddamn slow, I need fast computation from String, like pre-prepared calculator.

 

Draco  - this is what I don't really feel like doing

Is there some library for such stuff? Must be (looking), maybe someone used such?

 

EDIT

And by fast I mean FPS-time (suitable to be ran per-tick or even render loop)

[Draco18s]

Draco  - this is what I don't really feel like doing

 

Tough.  Because that's what you're trying to do.

[ItsAMysteriousYT]

Yep And if youz write a good parser, it will be fast. Just set break; and if-stuff right and it will run fast.

[jabelar]

Why are you concerned about performance -- do you really need to run this every tick?

 

In terms of performance optimization, generally you should only worry about it if it is proven to be a problem. You shouldn't be stupid about performance, but you also shouldn't compromise the goal of making simple, logical, readable code unless truly necessary. A parser would be very logical and readable, so I'd only get fancy if needed.

[Ernio]

Here we go!

 

 

Note:

If any of you has something that you can honestly recommend on dynamic compilation - feel free to post. Right now I got some googles, slowly molding the idea of my quest here.

[AnZaNaMa]

Why the crap don't you just save these values in NBT...?

[Ernio]

I think you didn't understand what the topic is about. I don't save, I compute.

[jabelar]

How complicated and varied are your formulae? If there is any regularity you could come up with your own notation that is easy to transform, like how linear algebraic equations can be represented by a matrix.

 

I guess technically that is still a "parser" but it would be very easy to implement as a calculation.