| From phr Tue Jul 8 10:36:19 1986 |
| Date: Tue, 8 Jul 86 00:52:24 EDT |
| From: phr (Paul Rubin) |
| To: riferguson%watmath.waterloo.edu@CSNET-RELAY.ARPA, tower |
| Subject: Re: Bison documentation? |
| |
| The main difference between Bison and Yacc that I know of is that |
| Bison supports the @N construction, which gives you access to |
| the starting and ending line number and character number associated |
| with any of the symbols in the current rule. |
| |
| Also, Bison supports the command '%expect N' which says not to mention |
| the conflicts if there are N shift/reduce conflicts and no reduce/reduce |
| conflicts. |
| |
| The differences in the algorithms stem mainly from the horrible |
| kludges that Johnson had to perpetrate to make Yacc fit in a PDP-11. |
| |
| Also, Bison uses a faster but less space-efficient encoding for the |
| parse tables (see Corbett's PhD thesis from Berkeley, "Static |
| Semantics in Compiler Error Recovery", June 1985, Report No. UCB/CSD |
| 85/251), and more modern technique for generating the lookahead sets. |
| (See Frank DeRemer and Thomas Pennello, "Efficient Computation of |
| LALR(1) Look-Ahead Sets", ACM Transactions on Programming Languages |
| and Systems (TOPLAS) 4, 4 (October 1982), 615-649. Their |
| technique is the standard one now.) |
| |
| paul rubin |
| free software foundation |
| |
| |
| [DeRemer-Pennello reference corrected by Paul Eggert <eggert@cs.ucla.edu>, |
| 2004-06-21.] |
