{"ID":2868758,"CreatedAt":"2026-06-01T04:54:23.091178241Z","UpdatedAt":"2026-06-01T04:54:23.091178241Z","DeletedAt":null,"paper_url":"https://arxiv.org/abs/2509.15834","arxiv_id":"2509.15834","title":"Automatic layout of railroad diagrams","abstract":"Railroad diagrams (also called \"syntax diagrams\") are a common, intuitive visualization of grammars, but limited tooling and a lack of formal attention to their layout mostly confines them to hand-drawn documentation. We present the first formal treatment of railroad diagram layout along with a principled, practical implementation. We characterize the problem as compiling a *diagram language* (specifying conceptual components and how they connect and compose) to a *layout language* (specifying basic graphical shapes and their sizes and positions). We then implement a compiler that performs *line wrapping* to meet a target width, as well as vertical *alignment* and horizontal *justification* per user-specified policies. We frame line wrapping as an optimization problem, where we describe principled dimensions of optimality and implement corresponding heuristics. For front-end evaluation, we show that our diagram language is well-suited for common applications by describing how regular expressions and Backus-Naur form can be compiled to it. For back-end evaluation, we argue that our compiler is practical by comparing its output to diagrams laid out by hand and by other tools.","short_abstract":"Railroad diagrams (also called \"syntax diagrams\") are a common, intuitive visualization of grammars, but limited tooling and a lack of formal attention to their layout mostly confines them to hand-drawn documentation. We present the first formal treatment of railroad diagram layout along with a principled, practical im...","url_abs":"https://arxiv.org/abs/2509.15834","url_pdf":"https://arxiv.org/pdf/2509.15834v1","authors":"[\"Shardul Chiplunkar\",\"Clément Pit-Claudel\"]","published":"2025-09-19T10:13:03Z","proceeding":"cs.PL","tasks":"[\"cs.PL\"]","methods":"[]","has_code":false}