Variables

Nodora has three kinds of names you can use inside a rule:

• Locals — named results of an expression, scoped to the rule.
• Outputs — locals also exposed in the evaluation result.
• input — the implicit, read-only object passed at evaluation time.

Local bindings

rule Example {
    is_adult = input.age >= 18
    in_us    = input.country == "us"
    eligible = is_adult && in_us
}

Each name is bound by a single = assignment. Names must be declared before use — forward references are rejected by the semantic analyzer.

Bindings are immutable. Reassigning a name is a compile-time error:

rule Bad {
    x = 1
    x = 2   // error: duplicate definition
}

There are no let, var, or const keywords — every assignment is a fresh, immutable binding.

Outputs

Prefixing an assignment with out adds it to the rule's result map under the same name:

rule Approval {
    eligible = input.age >= 18 && input.email_verified
    out approved = eligible
}

Output names must be unique. The value of an output can still be referenced by later statements just like a local.

A rule with no out statements is valid — it simply returns an empty outputs map and is only useful for its emitted signals.

The input object

input is reserved. It always has type object and is provided by the caller of the evaluator:

rule Demo {
    name    = input.user.name           // dot access
    role    = input["user"]["role"]     // bracket access
    first   = input.tags[0]             // array index
}

Reading a missing field returns undefined. undefined propagates through arithmetic, comparison and most built-ins, so partial inputs generally do not produce evaluation errors — they produce undefined outputs, which are omitted from the result.

Scope

Every rule has its own scope. Names declared inside one rule are not visible in another:

rule A { x = 1 }
rule B { y = x }   // error: 'x' is not defined

Naming

Identifiers start with a letter or underscore and contain letters, digits, or underscores. The keywords listed in Basics cannot be used as names, and input is reserved.