Return to the
comp.compilers page.
Search the
comp.compilers archives again.
| Related articles |
|---|
| how to eliminate this left recursion hammeron56@yahoo.com (Mike) (2005-07-22) |
| Re: how to eliminate this left recursion codeworker@free.fr (=?iso-8859-1?q?C=E9dric_LEMAIRE?=) (2005-07-26) |
| Re: how to eliminate this left recursion cfc@shell01.TheWorld.com (Chris F Clark) (2005-07-26) |
| Re: how to eliminate this left recursion owong@castortech.com (Oliver Wong) (2005-07-26) |
| From: | Chris F Clark <cfc@shell01.TheWorld.com> |
| Newsgroups: | comp.compilers |
| Date: | 26 Jul 2005 13:17:52 -0400 |
| Organization: | The World Public Access UNIX, Brookline, MA |
| References: | 05-07-083 |
| Keywords: | parse |
| Posted-Date: | 26 Jul 2005 13:17:52 EDT |
Mike wrote:
> I understand how to eliminate left-recursion when a grammar rule
> looks like this: a->ab | c
...
> ERE_expression : one_character_ERE
> | '^'
> | '$'
> | '(' extended_reg_exp ')'
> | ERE_expression ERE_dupl_symbol
> ;
It is of the form a -> ab | c
a : ERE_expression
b : ERE_dupl_symbol
c : one_character_ERE
| '^'
| '$'
| '(' extended_reg_exp ')'
Now, apply the transformation as you know it...
It it were truly of the form a -> ab with no other alternative(s), then
unless b -> null, there is no solution, and if b -> null there is only
one solution a -> null.
Hope this helps,
-Chris
*****************************************************************************
Chris Clark Internet : compres@world.std.com
Compiler Resources, Inc. Web Site : http://world.std.com/~compres
23 Bailey Rd voice : (508) 435-5016
Berlin, MA 01503 USA fax : (978) 838-0263 (24 hours)
------------------------------------------------------------------------------
Return to the
comp.compilers page.
Search the
comp.compilers archives again.