neilparikh / rules-engine

A rule engine for allowing users to rules over data in your application

Running the example

$ stack build
$ cat example.txt | stack exec rules-engine-exe

Usage

You can find an example of how use this in app/Main.hs.

The flow is:

1. Use parseRule to receive an Either ParseError Rule.
2. If you have a Right rule, pass that to validateRule, along with a list of all the valid actions, and a list of all the valid variables.
   • This is a separate function call, so that you can surface a failure to the user.
3. If validateRule returns True, pass the rule, along with Map from variable names to their value, a Map from actions, to their callback functions, and a context value to pass to the callback if it is triggered.
   • This context value is useful if you are running the rule against multiple sets of data, so that you can distinguish which data set triggered the rule.

rules-engine's Issues

Use phantom types/newtypes to ensure that only validated rules can be executed

Have validateRule return a value of type ValidatedRule (a newtype wrapper around rule with the constructor hidden), and then have runRule take in a ValidatedRule.

Replace read in intParser with maybeRead