Control flow

Summary

Control flow in Point appears inside calculation and rule bodies: loops, accumulation, and conditionals in label blocks.

Syntax

Iteration

record Cart Item
  unit price: Int
  quantity: Int

rule line totals
  input items: List<Cart Item>
  output total: Int
  total starts at 0
  for each item in items
    add item.unit price * item.quantity to total
  return total

Mutation in rules and calculations

rule adjust score
  input score: Int
  output total: Int
  total starts at score
  add 10 to total
  subtract 5 from total
  set total to 0
  return total

Conditional adds in rules

record Deploy Signals
  has bundle id: Bool

rule deploy readiness
  input signals: Deploy Signals
  output score: Int
  score starts at 0
  add 30 when signals.has bundle id
  return score

Labels

label score status
  input score: Int
  output Text
  when score >= 90 return "excellent"
  otherwise return "keep going"

Semantics

for each requires a List<T> iterable. Rule outputs initialized with starts at are mutable; calculation outputs using is are typically single assignment unless mutation forms are used.

Compiler note

for each requires a List<T>. Rule accumulators initialized with starts at may use add to, subtract from, and set to inside the body.

Example

From examples/cart-total.point:

module Checkout

record Cart Item
  name: Text
  unit price: Int
  quantity: Int

rule cart total
  input items: List<Cart Item>
  output total: Int
  total starts at 0
  for each item in items
    add item.unit price * item.quantity to total
  return total

Common mistakes

for each over a non-list (iteration-type-mismatch)
Assigning to an immutable binding (immutable-assignment)

Agent diagnostic notes

Loop diagnostics point at the for each span with repair text when the iterable is wrong
After fixing control flow, re-run point check-json before touching unrelated blocks