bison/doc/figs/example-reduce.txt

       .------------------.
       |     State 1      |
       | 3 a: "0" . [";"] |
       | 4 b: "0" . ["."] |
       `------------------'
             /     \
            /       \ ["."]
           /         \
          v           v
         / \         / \
        / R \       / R \
(green) \ 3 /       \ 4 / (green)
         \ /         \ /