Crown Docs

The docs frontend now supports fenced railroad blocks for grammar-style syntax diagrams.

Use this when a Mermaid flowchart would be too broad and you want to explain a concrete production rule, token pattern, or mini-language shape.

How the block works

the fence language is railroad
the block body is JSON
the JSON maps directly to the supported railroad-diagrams node types
a top-level array is treated as Diagram(items) automatically
bare strings inside items become Terminal(...)

Supported node types

Type	Required fields	Notes
`Terminal`	`text`	Literal token or fixed keyword
`NonTerminal`	`text`	Production or placeholder label
`Comment`	`text`	Annotation text
`Skip`	none	Empty branch / spacer
`Sequence`	`items`	Concatenation
`Choice`	`items`	Optional `normal` chooses the straight path
`Optional`	`item`	Optional `skip: "skip"` keeps omission on the main line
`OneOrMore`	`item`	Optional `repeat` item between repetitions
`ZeroOrMore`	`item`	Optional `repeat` and `skip` just like the library
`Diagram`	`items`	Explicit root
`ComplexDiagram`	`items`	Explicit complex root

Source example

[
  { "type": "NonTerminal", "text": "identifier" },
  {
    "type": "ZeroOrMore",
    "item": {
      "type": "Sequence",
      "items": [".", { "type": "NonTerminal", "text": "identifier" }]
    }
  }
]

Rendered example

Rendering railroad diagram…

Choice example