Example for the DA.Logic module

The DA.Logic module seems to be interesting, but it’s not immediately obvious to me how I can use it.

Could you show me an example?

I think the formulas Formula t from DA.Logic are best thought of as limited serializable functions (t -> Bool) -> Bool. A common option is Formula Text where your texts are some sort of identifiers (I’ve seen asset ids used but really anything works). You can store that formula on a template e.g. as eligibility rules and then evaluate it in a choice via interpret where you map each t to a boolean.

I don’t have a publicly available example unfortunately.

Thank you!

I leave this question open for a few days in case somebody can show me concrete examples.

This is what I could come up with based on your explanation:

module Logic where 

import DA.Logic
import Daml.Script

a = Proposition "abrakadabra" 
h = Proposition "hocuspocus"
d = Proposition "dracaeris"
e = Proposition "expectopatronum"

truthFunction : Text -> Optional Bool 
truthFunction "abrakadabra" = Some True 
truthFunction "hocuspocus" = Some False 
truthFunction "dracaeris" = Some False 
truthFunction _ = None

formula1 = disj [a,h,d]
formula2 = conj [a,h,d]
formula3 = disj [a,h,e]

test = script do 
    debug $ "formula1 interpreted: " <> show (interpret truthFunction formula1)
    debug $ "formula2 interpreted: " <> show (interpret truthFunction formula2)
    debug $ "formula3 interpreted: " <> show (interpret truthFunction formula3)

Results:

Trace: 
  "formula1 interpreted: Right True"
  "formula2 interpreted: Right False"
  "formula3 interpreted: Right True"