On 2004 nov 22, at 17:48, Frank-Andre Riess wrote:
Hi there folks,
once again, I've got a question related to Happy (I've got version 1.13 at the moment). Maybe, it's even more a question on formal languages, but well... How can I write a grammar that can cope with user-defined operators (of different precedences/associativities) and compound expression like function calls, if-then-else- and case-statements and the like. I tried to write it down straight forwardly, but failed terribly (alas, I didn't keep it, so I can't show you - if someone of you is versed in this issue, I can try to explain the language's constructs).
One way of doing this using combinator based parsing (where you can generate parsers dynamically) is to read the fixity declarations, and to use the result of this to build the precedence parser. This idea has been sketched in:
S. D. Swierstra and P. R. Azero Alcocer. Fast, Error Correcting Parser Combinators: a Short Tutorial. In J. Pavelka, G. Tel, and M. Bartosek, editors, SOFSEM'99 Theory and Practice of Informatics, 26th Seminar on Current Trends in Theory and Practice of Informatics, volume 1725 of LNCS, pages 111--129, November 1999.
If you do not have access to this I will be happy to send it to you,
Doaitse Swierstra
Thank you very much. I don't know much about combinator based parsing, however (or maybe just therefor) I'm interested in having a closer look at it. I'd be obliged if you sent me your paper.