Predicator

Predicator is a safe (does not eval code), admin or business user facing predicate engine. It turns a string predicate like "score >= 600 or (score > 580 and monthly_income > 9000)" along with a supplied context into a true or false. This predicate can be stored as an attribute of a model (ex: an Offer model could store a predicate indicating if it is available to a customer).

This project provides a Go Evaluator - the parsing and compilation needs to happen in Ruby or JavaScript.

Usage

Assuming Predicator compiled the string score >= 600 or (score > 580 and income > 9000) to the instructions:

[
  [ "load", "score" ],
  [ "to_int" ],
  [ "lit", 600 ],
  [ "compare", "GTE" ],
  [ "jtrue", 11 ],
  [ "load", "score" ],
  [ "to_int" ],
  [ "lit", 580 ],
  [ "compare", "GT" ],
  [ "jfalse", 5 ],
  [ "load", "income" ],
  [ "to_int" ],
  [ "lit", 9000 ],
  [ "compare", "GT" ]
]

Simple usage:

data := make(map[string]interface{}, 8)
e := NewEvaluator(instructions, data)
result := e.result()
// result is now set to false

Now add data to make the predicate pass:

data := make(map[string]interface{}, 8)
data["score"] = 590;
data["income"] = 9500;
e := NewEvaluator(instructions, data)
result := e.result()
// result is now set to false

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/riddler/predicator-go. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The library is available as open source under the terms of the MIT License.