{
  "name": "Value functions",
  "description": "A { \"call\": ... } expression invokes a value function registered in C# (RuleWrightBuilder.RegisterValueFunction(\"RoundTo\", ...)). The document names the function; the behaviour stays registered code, and an unregistered name fails at load. Calls work anywhere an expression does: action values, a condition's left-hand side, decision-table cells.",
  "rules": [
    {
      "id": "rounded-discount",
      "description": "call composes with the built-in operators: round(Total * 0.1) to 2 digits.",
      "condition": { "field": "Order.Total", "operator": "GreaterThanOrEqual", "value": 50 },
      "actions": [
        {
          "type": "setOutput",
          "target": "Discount",
          "value": {
            "call": "RoundTo",
            "operands": [
              { "op": "multiply", "operands": [ { "field": "Order.Total" }, 0.1 ] },
              2
            ]
          }
        }
      ]
    },
    {
      "id": "big-rounded-total",
      "description": "A call as a condition's computed left-hand side.",
      "condition": {
        "expression": { "call": "RoundTo", "operands": [ { "field": "Order.Total" }, 0 ] },
        "operator": "GreaterThanOrEqual",
        "value": 150
      },
      "actions": [
        { "type": "setOutput", "target": "BigOrder", "value": true }
      ]
    }
  ]
}