EBNF causes java.lang.IllegalStateException

Question

To quote the Wikipedia:

Even EBNF can be described using EBNF. Consider below grammar (using conventions such as "-" to indicate set disjunction, "+" to indicate one or more matches, and "?" for optionality)

However, when I run the provided EBNF through PlantUML, I get:

You should send a mail to plantuml@gmail.com or post 
to https://plantuml.com/qa with this log 
(V1.2023.10beta2) java.lang.IllegalStateException

Answer 1

Hello P., and all,

It is [currently] normal.
→ Because current implementation use only 'ISO EBNF' form.

Then:

@startebnf
concatenation = ( S , factor , S , "," ? ) + ;
@endebnf

is not a ISO BNF form!

You must use ISO EBNF:

The Wikipedia [simplified] grammar (using conventions)	ISO EBNF
"+" to indicate one or more matches	{ }- form
"?" for optionality	[ ] form

Then here is the expected result:

@startebnf
concatenation = { S , factor , S , [","] }- ;
@endebnf

---

Or use RegEx, like:

@startregex
concatenation = (( S )( factor )( S ) ,?)+;
@endregex

---

See also doc. here:

• https://plantuml.com/ebnf
• https://plantuml.com/regex

If that can help,
Enjoy,
Regards,
Th.

Comments

I think we should look into common "extensions" like this at some point.