|LR(0) and Lookaheads firstname.lastname@example.org (Will) (2001-11-04)|
|Re: LR(0) and Lookaheads email@example.com (Thant Tessman) (2001-11-08)|
|Re: LR(0) and Lookaheads firstname.lastname@example.org (J.H.Jongejan) (2001-11-08)|
|Date:||4 Nov 2001 23:54:14 -0500|
|Organization:||Excite@Home - The Leader in Broadband http://home.com/faster|
|Posted-Date:||04 Nov 2001 23:54:14 EST|
The new dragon book gives an algorithm for constructing parsing tables
for LR(1) grammars. The '1' is suppose to be 1 lookahead. If you can
construct such an LR(1) parsing table without conflicts for a given
grammar, then the grammar is LR(1) grammar.
Is lookahead and the current input symbol the same thing?
I had thought that LR(0) was just another way of saying SLR(1) because
in constructing SLR(1) grammars, LR(0) items are used. However I am
wrong. As a matter of fact, LR(0) grammars are "smaller" than SLR(1)
grammars. So how do I test a grammar to see if it is LR(0) grammar
(i.e. where in the new dragon is this explained ... how do you
construct a LR(0) parsing table)? Also the '0' in LR(0) grammars means
0 lookahead? That does not make sense, unless I am not understanding
what lookahead means. If you don't look at any input symbols, how are
you suppose to parse the input string?
Thanks in advance.
Return to the
Search the comp.compilers archives again.