#Moon PolicyForge

Explainable rule decisions, implemented in MoonBit with a JSON CLI and reusable library API.

Repository: https://github.com/123123213weqw/moon-policyforge
Package: 123123213weqw/moon_policyforge@0.1.0
License: Apache-2.0
Release scope: 0.1.0 initial implementation. The broader competition proposal in docs/proposal.md is a reference design, not a claim that every planned capability is implemented.

#Implemented

An expression lexer and precedence parser; numeric/string/boolean literals; dotted fact paths; arithmetic and comparisons; strict boolean short circuit; exists/len/contains/lower/abs; finite arithmetic; evaluation budgets; rule priority; first/all/unique decisions; conflict flags; per-record errors; condition traces; rule-set diff.

#Build and run

Use MoonBit and Node.js 24. The core library supports JS, wasm, wasm-gc and native; the filesystem/HTTP/process CLI is JS only.

moon update
moon build --target js
moon run cmd/main --target js -- examples/scenario-1.json
node _build/js/debug/build/cmd/main/main.js examples/scenario-1.json

Pass - to read a UTF-8 JSON request from stdin. A single request must be at most 16 MiB. Successful requests print one JSON result; invalid requests exit nonzero. The host runner is a separate process and does not edit the input request file.

#Library use

moon add 123123213weqw/moon_policyforge@0.1.0

In the consumer's moon.pkg:

import {
  "123123213weqw/moon_policyforge" @engine,
  "moonbitlang/core/json",
}

fn example(request : Json) -> Json raise {
  @engine.execute(request)
}

execute(Json) -> Json raise is the standard JSON boundary. from_json, Value::to_json, and run(Value) -> Value raise provide a typed semantic value interface. Object ordering is not significant; numeric values use finite Double. Public domain functions are listed in pkg.generated.mbti.

#Tests

moon test --target js
moon test --target wasm
moon test --target wasm-gc
moon test --target native  # requires a C compiler
moon build --target js
node scripts/check.mjs
python -B scripts/reference.py

There are 9 checked fixture cases in tests/cases.json, executed both in MoonBit white-box tests and through the actual Node CLI. Independent reference checks use Python's standard library or separately written algorithms. Fixtures are synthetic and are not presented as production adoption evidence. See input and output examples and current boundaries.

#Current boundaries

A custom bounded expression language. No arbitrary code execution, loops, user functions or external I/O. Runtime types are checked; static type inference is not included. All matching rule outputs are evaluated even in first mode, and first selects the highest-priority match; equal priority uses rule ID order. Unique produces conflict and null decision on multiple matches. Facts are caller supplied. Traces can include fact values, so redact sensitive facts before storing reports.

See source and dependency attribution. This release does not establish competition eligibility or organizer acceptance.

InputError

source

pub(all) suberror InputError {
  InputError(String)
} derive(Eq, Show)

Evaluation

source

type Evaluation

Expression

source

pub(all) enum Expression {
  Literal(Value)
  Variable(String)
  Unary(String, Expression)
  Binary(String, Expression, Expression)
  Call(String, Array[Expression])
}

Parser

source

type Parser

Rule

source

type Rule

Value

source

pub(all) enum Value {
  Null
  Bool(Bool)
  Number(Double)
  String(String)
  Array(Array[Value])
  Object(Map[String, Value])
} derive(Eq, @moonbitlang/core/debug.Debug
Debug)

Value::stringify

source

fn Value::stringify(self : Value) -> String

Value::to_json

source

fn Value::to_json(self : Value) -> Json

compile

source

fn compile(source : String) -> Expression raise

evaluate_expression

source

fn evaluate_expression(source : String, facts : Value, budget? : Int) -> Value raise

execute

source

fn execute(request : Json) -> Json raise

from_json

source

fn from_json(value : Json) -> Value

run

source

fn run(request : Value) -> Value raise

Source Files

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moon_policyforge

#Moon PolicyForge

#Implemented

#Build and run

#Library use

#Tests

#Current boundaries

#InputError

#Evaluation

#Expression

#Parser

#Rule

#Value

#Value::stringify

#Value::to_json

#compile

#evaluate_expression

#execute

#from_json

#run

Source Files

InputError

Evaluation

Expression

Parser

Rule

Value

Value::stringify

Value::to_json

compile

evaluate_expression

execute

from_json

run