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1.1 ! root 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%[email protected], 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:
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