ludic/examples/ecs/world_scan.ludic

# world_scan.ludic — EV2b reflection: scan the world and identify each entity by
# MODEL, by name (replaces tests/mod_c/world_scan.c). world_count / world_kind /
# world_model_id let a mod walk every entity and pick out a model's instances, then
# read their fields with world_get. Two Units (hp 50, 60) → count 2, sum 110.
program WorldScan {
  property Health { hp: int = 0, max: int = 0 }
  model Unit { Health }
  @Public @OnSpawn(Unit) handler Init { Health.hp = Health.max }

  entry {
    spawn Unit { Health { max: 50 } }
    spawn Unit { Health { max: 60 } }
    let H  = world_prop_id("Health")
    let hp = world_field_id(H, "hp")
    let Um = world_model_id("Unit")
    let n  = world_count()
    var count = 0
    var sum   = 0
    var e = 0
    while e < n {
      if world_kind(e) == Um {
        count += 1
        sum += world_get(e, H, hp)
      }
      e += 1
    }
    print(count)   # 2
    print(sum)     # 110
  }
}