trying to create DSL to generate sequences ... here is what i did so far :
?start : expr
token : WORD
repeat_token : token ":" INT
tokens : (token | repeat_token)+
repeat : ":" INT
expr : "(" tokens | expr ")" repeat?
here is how the DSL look like :
(a b:2 (c d:3):2 ):3
[[a bb [[c ddd] [c ddd]] ] ... ]
I have problem with expr within expr ... ?
this fails:
(a:2 (b))
How do you see fitting (a:2 (b)) into your grammar? It doesn't seem like you can. Here's my logic:
The outer level has to be an expr because of the parens. In that expr you have both a repeat_token and another expr. I don't see anywhere that lets you have a sequence of elements that includes both repeat_tokens and exprs. Because of that, your input can't be parsed with your grammar.
As it is, a expr can only be in another expr all by itself, which doesn't seem very useful in general. That could only lead to extra sets of parentheses I think. What I think you need to do is allow an expr to be included in a tokens.
So then maybe:
?start : expr
token : WORD
repeat_token : token ":" INT
tokens : (token | repeat_token | expr)+
repeat : ":" INT
expr : "(" tokens ")" repeat?