Question: would it make sense to be able to add a fact whose functions can be called without a fact prefix

[tpihl]

Is your feature request related to a problem? Please describe.
I really like the functions we can put in rules. But based on the actual rule engine implementatiton it may make sense to be able to add more functions not related to a fact (since there is no fact data, only functions).

I'm currently using facts like "helper" or "action" or similar, but it really remove some of the readability/flow in the rule. One example from one of my "then" sections where "helper" only raise questions when the rule is read by humans:

fact1.Data1 = helper.CalculateSomethingMakeingSenseInThisRuleengine(fact1.Data2)

or in a "with" statement

helper.EstimatedValueOf(fact1) > 7

Describe the solution you'd like
fact1.Data1 = CalculateSomethingMakeingSenseInThisRuleengine(fact1.Data2)

EstimatedValueOf(fact1) > 7

Describe alternatives you've considered
Not really, only a question on possible improved readability and simplification of rules (by adding some magic)

Additional context
Same context as my other question #172

[newm4n]

HI @tpihl

The helper approach is the intended approach by design for users to define their own function.
If you wish to have it as a built-in function,

Solution 1 : You can simply fork this repo and add your custom function in ast/BuiltInFunctions.go.

Instead of using github.com/hyperjumptech/grule-rule-engine, you use your own repo.

Its quite common to do this way, as you may observe many people fork this project to do it this way. You can create a PR if you think the function is generic enough for other user to use. I think this is the simplest, fastest alternative.

Solution 2 : To add func into data context (Its an idea, not yet implemented in current version), as in.

// create an anonymous function
myfunc = func (param string) {
    ...
} 

// add the function into data context
dataCtx.add("MyFunc", myFunc)

and from the rule you can use

then
     MyFunc("Something");

I have few downside in this approach, you have to add the function everytime you create Datacontext, to make the function
available every-time. I will consider to implement this though...

[tpihl]

Hi newwm4n,

That makes sense. Running with my own fork isn't really my thing, i think this is good software and that should be visible.

The solution to add the function in every call is the same no matter if it's a helper or not, so not really a downside, is it?

Would if be possible to add the function when you create the knowledge-library?
It would then be part of the new instance and be ideally part on the same level as the rules parsed (i'd like to keep custom funktions on the same level as the rules they support).

If not, i'd be happy happy with adding the function to every fact, no problem. I already have a wrapper handlingen the different facts for some other reasons.

[newm4n]

Would if be possible to add the function when you create the knowledge-library?

No, i'm afraid not.