Reference Statements

Statements Reference

This document provides a complete reference for all statement types in ARO.

ARO Statement

The fundamental statement type following the Action-Result-Object pattern.

Syntax

Action [article] <result> preposition [article] <object> [modifiers].

Components

Component	Required	Description
Action	Yes	Plain action verb (no angle brackets)
Article	No	a, an, or the
Result	Yes	Output variable
Preposition	Yes	Relationship word
Object	Yes	Input/target
Modifiers	No	where, with, on, when clauses

Examples

Extract the <user-id> from the <request: parameters>.
Create a <user> with <user-data>.
Return an <OK: status> for the <request>.
Store the <order> into the <order-repository>.
Retrieve the <user> from the <repository> where id = <user-id>.
Start the <http-server> on port 8080.

Publish Statement

Makes a variable globally accessible across feature sets.

Syntax

Publish as <alias> <variable>.

Components

Component	Description
alias	Name to publish under
variable	Variable to publish

Example

Read the <config> from the <file: "./config.json">.
Publish as <app-config> <config>.

Guarded Statement (when)

Conditionally executes a statement based on a condition. If the condition is false, the statement is skipped.

Syntax

Action the <result> preposition the <object> when <condition>.

Conditions

Condition	Description
<var> is <value>	Equality
<var> is not <value>	Inequality
<var> is empty	Null/empty check
<var> is not empty	Has value
<var> exists	Value exists
<var> is null	Null check
<var> > <value>	Greater than
<var> < <value>	Less than
<var> >= <value>	Greater or equal
<var> <= <value>	Less or equal
<cond1> and <cond2>	Both true
<cond1> or <cond2>	Either true
not <cond>	Negation

Examples

(* Return not found only when user is empty *)
Return a <NotFound: status> for the <missing: user> when <user> is empty.

(* Send notification only when user has email *)
Send the <notification> to the <user: email> when <user: email> exists.

(* Log admin access only for admins *)
Log <admin-access> to the <audit> when <user: role> = "admin".

(* Early exit on invalid input *)
Return a <BadRequest: status> for the <invalid: amount> when <amount> <= 0.

(* Combined conditions *)
Grant the <access> for the <user> when <user: active> is true and <user: verified> is true.

Usage Pattern

(PUT /users/{id}: User API) {
    Extract the <user-id> from the <request: parameters>.
    Extract the <updates> from the <request: body>.

    (* Early exit guards *)
    Return a <BadRequest: status> for the <missing: id> when <user-id> is empty.
    Return a <BadRequest: status> for the <missing: data> when <updates> is empty.

    (* Continue with valid input *)
    Retrieve the <user> from the <repository> where id = <user-id>.
    Return a <NotFound: status> for the <missing: user> when <user> is empty.

    Transform the <updated-user> from the <user> with <updates>.
    Store the <updated-user> into the <repository>.
    Return an <OK: status> with <updated-user>.
}

Match Statement

Pattern matching for multiple cases.

Syntax

match <variable> {
    case <value1> {
        (* statements *)
    }
    case <value2> {
        (* statements *)
    }
    otherwise {
        (* fallback statements *)
    }
}

Case with Guard

match <variable> {
    case <value> where <condition> {
        (* statements *)
    }
}

Example

match <status> {
    case "pending" {
        Log "Order is pending" to the <console>.
    }
    case "shipped" {
        Log "Order has shipped" to the <console>.
        Emit an <OrderShipped: event> with <order>.
    }
    case "delivered" {
        Log "Order delivered" to the <console>.
        Emit an <OrderDelivered: event> with <order>.
    }
    otherwise {
        Log "Unknown status" to the <console>.
    }
}

Pattern Matching with Guards

match <user: subscription> {
    case <premium> where <user: credits> > 0 {
        Grant the <premium-features> for the <user>.
        Deduct the <credit> from the <user: account>.
    }
    case <premium> {
        Notify the <user> about the <low-credits>.
        Grant the <basic-features> for the <user>.
    }
    case <basic> {
        Grant the <basic-features> for the <user>.
    }
    otherwise {
        Redirect the <user> to the <subscription-page>.
    }
}

Return Statement

Exits the feature set with a response.

Syntax

Return [article] <status> [with <data>] [for <context>].

Status Codes

Status	HTTP Code	Usage
OK	200	Successful request
Created	201	Resource created
Accepted	202	Async operation started
NoContent	204	Success, no body
BadRequest	400	Invalid input
Unauthorized	401	Auth required
Forbidden	403	Access denied
NotFound	404	Not found
Conflict	409	Resource conflict
UnprocessableEntity	422	Validation failed
TooManyRequests	429	Rate limited
InternalError	500	Server error
ServiceUnavailable	503	Service down

Examples

Return an <OK: status> with <data>.
Return a <Created: status> with <resource>.
Return a <NoContent: status> for the <deletion>.
Return a <BadRequest: status> with <validation: errors>.
Return a <NotFound: status> for the <missing: user>.
Return a <Forbidden: status> for the <unauthorized: access>.

Comment

Adds documentation to code.

Syntax

(* comment text *)

Examples

(* This is a single-line comment *)

(*
   This is a
   multi-line comment
*)

(* Comments can be (* nested *) *)

(Process Order: Order Processing) {
    (* Extract order data from request *)
    Extract the <order-data> from the <request: body>.

    (* Validate before processing *)
    Validate the <order-data> for the <order-schema>.

    (* Store and return *)
    Store the <order> into the <repository>.
    Return a <Created: status> with <order>.
}

Where Clause

Filters data in retrieval and deletion.

Syntax

... where <field> = <value>
... where <field> = <value> and <field2> = <value2>

Examples

Retrieve the <user> from the <repository> where id = <user-id>.
Retrieve the <orders> from the <repository> where status = "pending".
Retrieve the <users> from the <repository> where role = "admin" and active = true.
Delete the <sessions> from the <repository> where userId = <user-id>.

With Clause

Provides additional data or parameters.

Syntax

... with <variable>
... with <object-literal>
... with <string-literal>

Examples

Create the <user> with <user-data>.
Create the <config> with { debug: true, port: 8080 }.
Transform the <updated> from the <user> with <updates>.
Send the <message> to the <connection> with "Hello, World!".
Log "Application started" to the <console>.

On Clause

Specifies ports for network operations.

Syntax

... on port <number>

Examples

Start the <http-server> on port 8080.
Listen on port 9000 as <socket-server>.
Connect to <host: "localhost"> on port 5432 as <database>.

When Clause

Conditionally executes a statement.

Syntax

Action the <result> preposition the <object> when <condition>.

Examples

Return a <NotFound: status> for the <user> when <user> is empty.
Log "Low stock" to the <console> when <stock> < 10.
Send the <alert> to the <admin: email> when <errors> > <threshold>.

Statement Order

Statements execute sequentially from top to bottom:

(Process Request: Handler) {
    (* 1. First *)
    Extract the <data> from the <request: body>.

    (* 2. Second *)
    Validate the <data> for the <schema>.

    (* 3. Third *)
    Create the <result> with <data>.

    (* 4. Fourth *)
    Store the <result> into the <repository>.

    (* 5. Fifth - ends execution *)
    Return a <Created: status> with <result>.

    (* Never executed - after return *)
    Log "This won't run" to the <console>.
}

Statement Termination

All statements end with a period (.):

(* Correct *)
Extract the <data> from the <request>.
Return an <OK: status> with <data>.

(* Incorrect - missing period *)
Extract the <data> from the <request>

Match blocks use braces without periods on closing brace:

match <status> {
    case "active" {
        Return an <OK: status>.  (* Period on inner statement *)
    }
}  (* No period on closing brace *)