This backend outputs a scanner as a DOT document, for looking at the DFA while working on a set of rules. See scanner generator backends for the other backends.
A node is a state of the automaton, drawn as a double circle when it accepts a rule, and the arrow with no source marks the state a scan starts in. An edge is a transition, labelled with the characters it is taken on.
Render it with Graphviz:
golr scanner --frontend golr --frontend-file-path calculator.golr --backend dot --backend-file-path scanner.dot
dot -Tsvg scanner.dot -o scanner.svg