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Fix some comments concerning LR(0) versus LALR(1).

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Stop equating LR(0) with nondeterminism and LALR(1) with
determinism.  That is, if all states are consistent, then LR(0)
tables are deterministic.  On the other hand, LALR(1) tables
might be nondeterministic before conflict resolution, and GLR
permits LALR(1) tables to remain nondeterministic.
* src/LR0.c, src/LR0.h: Here.
* src/lalr.c, src/lalr.h: Here.
* src/main.c (main): Here.
* src/state.c, src/state.h: Here.

* src/ielr.h (ielr): In preconditions, expect LR(0) not LALR(1)
parser tables.
This commit is contained in:
Joel E. Denny
2010-01-04 14:13:43 -05:00
parent 1462fcee1e
commit 1c4ad777cb
9 changed files with 32 additions and 17 deletions
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17
ChangeLog
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@@ -1,3 +1,20 @@
2010-01-04 Joel E. Denny <jdenny@clemson.edu>
Fix some comments concerning LR(0) versus LALR(1).
Stop equating LR(0) with nondeterminism and LALR(1) with
determinism. That is, if all states are consistent, then LR(0)
tables are deterministic. On the other hand, LALR(1) tables
might be nondeterministic before conflict resolution, and GLR
permits LALR(1) tables to remain nondeterministic.
* src/LR0.c, src/LR0.h: Here.
* src/lalr.c, src/lalr.h: Here.
* src/main.c (main): Here.
* src/state.c, src/state.h: Here.
* src/ielr.h (ielr): In preconditions, expect LR(0) not LALR(1)
parser tables.
2010-01-04 Joel E. Denny <jdenny@clemson.edu>
maint: run "make update-copyright"

6
src/LR0.c
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@@ -1,4 +1,4 @@
/* Generate the nondeterministic finite state machine for Bison.
/* Generate the LR(0) parser states for Bison.
Copyright (C) 1984, 1986, 1989, 2000-2002, 2004-2007, 2009-2010 Free
Software Foundation, Inc.
@@ -329,8 +329,8 @@ set_states (void)
/*-------------------------------------------------------------------.
| Compute the nondeterministic finite state machine (see state.h for |
| details) from the grammar. |
| Compute the LR(0) parser states (see state.h for details) from the |
| grammar. |
`-------------------------------------------------------------------*/
void

3
src/LR0.h
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@@ -1,4 +1,5 @@
/* Generate the nondeterministic finite state machine for bison,
/* Generate the LR(0) parser states for Bison.
Copyright (C) 1984, 1986, 1989, 2000-2002, 2009-2010 Free Software
Foundation, Inc.

4
src/ielr.h
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@@ -26,8 +26,8 @@
/**
* \pre
* - \c ::states is of size \c ::nstates and defines an LALR(1) parser for
* the users's grammar.
* - \c ::states is of size \c ::nstates and defines an LR(0) parser
* for the users's grammar.
* - \c ::ntokens is the number of tokens in the grammar.
* \post
* - \c ::states is of size \c ::nstates (which might be greater than

3
src/lalr.c
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@@ -19,8 +19,7 @@
along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* Compute how to make the finite state machine deterministic; find
which rules need lookahead in each state, and which lookahead
/* Find which rules need lookahead in each state, and which lookahead
tokens they accept. */
#include <config.h>

3
src/lalr.h
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@@ -33,8 +33,7 @@
/** Build the LALR(1) automaton.
Compute how to make the finite state machine deterministic; find
which rules need lookahead in each state, and which lookahead
Find which rules need lookahead in each state, and which lookahead
tokens they accept.
Also builds:

9
src/main.c
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@@ -97,15 +97,14 @@ main (int argc, char *argv[])
nullable_compute ();
timevar_pop (TV_SETS);
/* Convert to nondeterministic finite state machine. In file LR0.
See state.h for more info. */
/* Compute LR(0) parser states. See state.h for more info. */
timevar_push (TV_LR0);
generate_states ();
timevar_pop (TV_LR0);
/* Make it deterministic by computing lookahead sets. Except when LALR(1) is
requested, split states to eliminate LR(1)-relative inadequacies. In file
lalr and ielr. */
/* Add lookahead sets to parser states. Except when LALR(1) is
requested, split states to eliminate LR(1)-relative
inadequacies. */
ielr ();
/* Find and record any conflicts: places where one token of

2
src/state.c
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@@ -1,4 +1,4 @@
/* Type definitions for nondeterministic finite state machine for Bison.
/* Type definitions for the finite state machine for Bison.
Copyright (C) 2001-2007, 2009-2010 Free Software Foundation, Inc.

2
src/state.h
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@@ -1,4 +1,4 @@
/* Type definitions for nondeterministic finite state machine for Bison.
/* Type definitions for the finite state machine for Bison.
Copyright (C) 1984, 1989, 2000-2004, 2007, 2009-2010 Free Software
Foundation, Inc.