0
  "Γ" := rules • "sum" [0-0]
  "sum" := rules • "sum" "plus" "sum" [0-0]
  "sum" := lexemes • "INT" [0-0]
1
  "sum" := lexemes "INT" • [0-1]
  "Γ" := rules "sum" • [0-1]
  "sum" := rules "sum" • "plus" "sum" [0-1]
  "plus" := lexemes • "PLUS" [1-1]