projects / bison.git / blame
| Commit | Line | Data |
|---|---|---|
| 07f68b11 RS |
1 | From phr Tue Jul 8 10:36:19 1986 |
| 2 | Date: Tue, 8 Jul 86 00:52:24 EDT | |
| 3 | From: phr (Paul Rubin) | |
| 4 | To: riferguson%watmath.waterloo.edu@CSNET-RELAY.ARPA, tower | |
| 5 | Subject: Re: Bison documentation? | |
| 6 | ||
| 7 | The main difference between Bison and Yacc that I know of is that | |
| 8 | Bison supports the @N construction, which gives you access to | |
| 9 | the starting and ending line number and character number associated | |
| 10 | with any of the symbols in the current rule. | |
| 11 | ||
| 12 | Also, Bison supports the command `%expect N' which says not to mention | |
| 13 | the conflicts if there are N shift/reduce conflicts and no reduce/reduce | |
| 14 | conflicts. | |
| 15 | ||
| 16 | The differences in the algorithms stem mainly from the horrible | |
| 17 | kludges that Johnson had to perpetrate to make Yacc fit in a PDP-11. | |
| 18 | ||
| 19 | Also, Bison uses a faster but less space-efficient encoding for the | |
| 20 | parse tables (see Corbett's PhD thesis from Berkeley, "Static | |
| 21 | Semantics in Compiler Error Recovery", June 1985, Report No. UCB/CSD | |
| 22 | 85/251), and more modern technique for generating the lookahead sets. | |
| 23 | (See "Efficient Construction of LALR(1) Lookahead Sets" by F. DeRemer | |
| 24 | and A. Pennello, in ACM TOPLS Vol 4 No 4, October 1982. Their | |
| 25 | technique is the standard one now.) | |
| 26 | ||
| 27 | paul rubin | |
| 28 | free software foundation | |
| 29 | ||
| 30 |