CODEWITHSUNDEEP
bisonbnfebnf
Nitrate
Nitrate

Reputation: 359

Extended BNF to BNF translation

I have this grammar in EBNF notation:

expr -> expr (opt1 | opt2 | opt3) expr

And i want to convert it to BNF to use it in Bison but i get shift/reduce errors in this:

expr : expr opt1 expr | expr opt2 expr | expr opt3 expr

I guess i misunderstood something along the way. Any help?

Thanks

Upvotes: 0

Views: 939

Answers (1)

Attila
Attila

Reputation: 28782

How about

expr: expr optexpr expr
optexpr: opt1 | opt2 | opt3

The shift/reduce erros are due to the overlapping expr prefixes. By introducing another definition, the parsing of expr becomes unambiguous.

Upvotes: 3

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