EBNF → SVG — Railroad Diagram Generation

The toolchain turns an EBNF grammar into one SVG railroad diagram per production. It chains a Java tool and two ooRexx scripts:

grammar.ebnf → rr.war (Java) → XHTML with embedded SVGs
             → extract_svg_from_rr_xhtml.rex → individual .svg files

ebnf2svg.rex is the orchestrator: it runs rr.war and then calls the extractor. You invoke only ebnf2svg.rex.

Prerequisites

ooRexx — the scripts use ooRexx-specific syntax and will not run on other Rexx interpreters.
Java 11+ on the PATH. On Debian/Ubuntu: apt-get install -y default-jre-headless.

Getting the toolchain

Put all three files in one directory (referred to as bin/ below).

rr.war — the Railroad Diagram Generator, by Gunther Rademacher. The download is a zip that contains rr.war; extract it:

curl -L -o rr.zip https://www.bottlecaps.de/rr/download/rr-2.6-java11.zip
unzip rr.zip rr.war -d bin/

The exact version may differ; check https://www.bottlecaps.de/rr for the current download. rr.war is an executable war (java -jar rr.war), so Java is all it needs.

The two ooRexx scripts — from the Rexx Parser distribution:

curl -L -o bin/ebnf2svg.rex \
  https://rexx.epbcn.com/rexx-parser/bin/ebnf2svg.rex
curl -L -o bin/extract_svg_from_rr_xhtml.rex \
  https://rexx.epbcn.com/rexx-parser/bin/extract_svg_from_rr_xhtml.rex

ebnf2svg.rex locates rr.war next to itself by default (override with --rr), and finds the extractor through the standard Rexx search order — so the simplest setup is all three in the same directory.

Usage

rexx bin/ebnf2svg.rex grammar

The argument is the grammar's path without the .ebnf extension — the script appends .ebnf itself. So grammar reads grammar.ebnf.

One SVG file is written per production, named after the production, in the same directory as the EBNF file.

Options:

--rr <path> — path to rr.war, if it is not next to ebnf2svg.rex.
--help, -h — usage.

If the extractor is not in the same directory as the orchestrator, point REXX_PATH at its directory so the search order can find it:

REXX_PATH=/path/to/bin rexx /path/to/bin/ebnf2svg.rex grammar

EBNF format

W3C-style EBNF, one production per line:

production_name ::= definition
Statement ::= 'IF' Expression 'THEN' Statement ( 'ELSE' Statement )?

Elements: 'KEYWORD' (terminal), name (non-terminal), ( ... | ... ) (alternatives), ? (optional), * (zero or more), + (one or more), [0-9] (character class), /* ... */ (comments).

Each production yields one SVG named after it (e.g. Statement.svg).

Notes

The orchestrator runs rr.war with -suppressebnf (no EBNF text beside the diagram) and -noinline (do not fold single-literal productions into their references), then extracts each embedded SVG into its own file with CRLF line endings. On success it exits zero; on error it prints a diagnostic and exits with a code identifying the failure: 2 bad usage (--rr without a path), 3 EBNF not found, 4 rr.war not found, 5 Java not found, 6 cannot create temp file, 7 rr.war error, 8 no output.