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9e6e7ed2b2
removing the old "look-ahead" spelling. Update previous look-ahead/lookahead change reports. * REFERENCES: look-ahead -> lookahead (since that's what he actually wrote). * doc/refcard.tex: look ahead -> lookahead, look-ahead -> lookahead
34 lines
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34 lines
1.3 KiB
Plaintext
From phr Tue Jul 8 10:36:19 1986
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Date: Tue, 8 Jul 86 00:52:24 EDT
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From: phr (Paul Rubin)
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To: riferguson%watmath.waterloo.edu@CSNET-RELAY.ARPA, tower
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Subject: Re: Bison documentation?
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The main difference between Bison and Yacc that I know of is that
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Bison supports the @N construction, which gives you access to
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the starting and ending line number and character number associated
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with any of the symbols in the current rule.
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Also, Bison supports the command `%expect N' which says not to mention
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the conflicts if there are N shift/reduce conflicts and no reduce/reduce
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conflicts.
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The differences in the algorithms stem mainly from the horrible
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kludges that Johnson had to perpetrate to make Yacc fit in a PDP-11.
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Also, Bison uses a faster but less space-efficient encoding for the
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parse tables (see Corbett's PhD thesis from Berkeley, "Static
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Semantics in Compiler Error Recovery", June 1985, Report No. UCB/CSD
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85/251), and more modern technique for generating the lookahead sets.
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(See Frank DeRemer and Thomas Pennello, "Efficient Computation of
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LALR(1) Look-Ahead Sets", ACM Transactions on Programming Languages
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and Systems (TOPLAS) 4, 4 (October 1982), 615-649. Their
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technique is the standard one now.)
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paul rubin
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free software foundation
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[DeRemer-Pennello reference corrected by Paul Eggert <eggert@cs.ucla.edu>,
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2004-06-21.]
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