# 27.3: a field a column mirrors is written only by a @RowVerb, which keeps the column with it
import "ludic.base"
program RowReducerColumn {
  property Deer {
    @Column x: int = 0
    fear: int = 0
  }
  state Herd { deer: Table<Deer> = null }
  action Push { @Target who: int = -1, dx: int = 1 }
  reducer Deer in Herd.deer on Push(r: mut Row<Deer>, a: Push) { r.rec.x += a.dx }
  entry { print(1) }
}