We see all the "railroad paths" through the syntactic combinations. Because it's not a recursive grammar, it's practical to unfold everything in one diagram. Instead of bubbles and arrows, he marked it up with LaTeX nested parentheses in 2D.
The whole guide is somewhat similar in flavor to the cheat sheets in mathematics books (trig identities, derivatives, integrals, useful equations, and so on).
https://en.wikipedia.org/wiki/Syntax_diagram
If we google for "syntax diagram" or "railroad diagram" there are better examples, like this one: https://i.stack.imgur.com/uDoc4.gif
We see all the "railroad paths" through the syntactic combinations. Because it's not a recursive grammar, it's practical to unfold everything in one diagram. Instead of bubbles and arrows, he marked it up with LaTeX nested parentheses in 2D.
The whole guide is somewhat similar in flavor to the cheat sheets in mathematics books (trig identities, derivatives, integrals, useful equations, and so on).