On Apr 18, 12:09 am, Pavel Panchekha <[email protected]> wrote: > In general, I've been very happy with PLY, especially considering how > terrible most parser generators are to work with. But one thing that > I've really missed with PLY is EBNF. I know, I know, its not strictly > necessary. The thing is, in a language I'm writing I've got the > following EBNF rule: > > > index : [expr] [':' [expr]] [':' [expr]] > > Which properly represents a python index (array subscript). The thing > is, this one EBNF rule boils down to 10 BNF rules. It gets worse - > functions have several optional parts. About four. That boils down to > 16 rules. And I'm thinking of making another part of function > definitions optional. With EBNF, that's easy, just add brackets. But > with BNF, that means double the number of rules. > > Any possibility of EBNF somewhere down the pipe?
The PLY documentation includes an example of creating an "optional" rule for some token/subrule. This can be easily employed to write the above EBNF rule in a single PLY rule (assuming expr_opt already exists). Eli --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "ply-hack" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/ply-hack?hl=en -~----------~----~----~----~------~----~------~--~---
