Production operators are operators that can be used in a production statement.
| whitespace | add node and connect with previous node, if any, by a successor edge |
| > | connect node with previous by a successor edge |
| < | connect node with previous by a reverse successor edge |
| <-> | connect node with previous by successor edges in both directions |
| --- | connect node with previous by a successor edge if there does not yet exist such an edge in either direction |
| +>, <+, <+>, -+- | as before, but branch instead of successor edges |
| />, </, </>, -/- | as before, but refinement instead of successor edges |
| -e->, <-e-, <-e->, -e- with an int-valued expression e | as before, but edges of type e instead of successor edges |
| -n-> with a node-valued expression n | create a compound edge with n encoding the edge data |
| <-n- with a node-valued expression n | as before, but reverse direction |
| [, ] | define the starts and the end of a branch connected subgraph |