jac-walker-patterns

Define a walker with has fields for state, add can abilities with with NodeType entry clauses that fire on arrival, and drive movement with visit [-->]. Spawn it with root spawn Walker() and read results from result.reports.

Declare a typed report channel with has reports: list[T] = [] and call report X once, typically from an exit ability after traversal completes. Omitting the = [] default makes reports a required spawn parameter and every spawn fails with E1050.

skip ends only the current ability while the walker continues processing its visit queue. disengage halts the entire walker immediately and discards queued visits, making it the right choice for search-style early exits.

The report statement both appends to result.reports and prints each value to stdout, which causes doubled output. Accumulate matches in a has list during traversal and report once from an exit ability instead of reporting per match.

If a walker never calls visit and only runs one entry ability that reports a value, it should be a def:pub function. Parameters replace has fields, a typed return replaces report, and callers avoid the result.reports unwrap.

Use visit [here-->[?:Type, field == value]] else { ... } where the else body runs only when the visit enqueued nothing. Inside else, connect a fresh node with ++> and visit it so the same downstream ability runs whether the node was found or created.