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RedHat 9 (Linux i386) - man page for antlr (redhat section 1)

ANTLR(1)				PCCTS Manual Pages				 ANTLR(1)

NAME
       antlr - ANother Tool for Language Recognition

SYNTAX
       antlr [options] grammar_files

DESCRIPTION
       Antlr  converts	an  extended form of context-free grammar into a set of C functions which
       directly implement an efficient form  of  deterministic	recursive-descent  LL(k)  parser.
       Context-free  grammars  may  be	augmented with predicates to allow semantics to influence
       parsing; this allows a form of context-sensitive parsing.  Selective backtracking is  also
       available to handle non-LL(k) and even non-LALR(k) constructs.  Antlr also produces a def-
       inition of a lexer which can be automatically converted into C code for a DFA-based  lexer
       by  dlg.   Hence,  antlr  serves a function much like that of yacc, however, it is notably
       more flexible and is more integrated with a lexer generator (antlr directly generates  dlg
       code, whereas yacc and lex are given independent descriptions).	Unlike yacc which accepts
       LALR(1) grammars, antlr accepts LL(k) grammars in an extended BNF notation -- which elimi-
       nates the need for precedence rules.

       Like  yacc grammars, antlr grammars can use automatically-maintained symbol attribute val-
       ues referenced as dollar variables.  Further, because antlr  generates  top-down  parsers,
       arbitrary  values  may  be  inherited from parent rules (passed like function parameters).
       Antlr also has a mechanism for creating and manipulating abstract-syntax-trees.

       There are various other niceties in antlr, including the ability  to  spread  one  grammar
       over  multiple files or even multiple grammars in a single file, the ability to generate a
       version of the grammar with actions stripped out (for documentation  purposes),	and  lots
       more.

OPTIONS
       -ck n  Use  up  to  n  symbols  of  lookahead when using compressed (linear approximation)
	      lookahead.  This type of lookahead is very cheap to compute and is attempted before
	      full  LL(k)  lookahead,  which  is of exponential complexity in the worst case.  In
	      general, the compressed lookahead can be much deeper (e.g, -ck 10)  than	the  full
	      lookahead (which usually must be less than 4).

       -CC    Generate C++ output from both ANTLR and DLG.

       -cr    Generate a cross-reference for all rules.  For each rule, print a list of all other
	      rules that reference it.

       -e1    Ambiguities/errors shown in low detail (default).

       -e2    Ambiguities/errors shown in more detail.

       -e3    Ambiguities/errors shown in excruciating detail.

       -fe file
	      Rename err.c to file.

       -fh file
	      Rename stdpccts.h header (turns on -gh) to file.

       -fl file
	      Rename lexical output, parser.dlg, to file.

       -fm file
	      Rename file with lexical mode definitions, mode.h, to file.

       -fr file
	      Rename file which remaps globally visible symbols, remap.h, to file.

       -ft file
	      Rename tokens.h to file.

       -ga    Generate ANSI-compatible code (default case).  This has not been rigorously  tested
	      to  be  ANSI XJ11 C compliant, but it is close.  The normal output of antlr is cur-
	      rently compilable under both K&R, ANSI C, and C++--this option does nothing because
	      antlr  generates	a  bunch  of #ifdef's to do the right thing depending on the lan-
	      guage.

       -gc    Indicates that antlr should generate no C code, i.e., only perform analysis on  the
	      grammar.

       -gd    C  code is inserted in each of the antlr generated parsing functions to provide for
	      user-defined handling of a detailed parse trace.	The  inserted  code  consists  of
	      calls  to  the  user-supplied  macros or functions called zzTRACEIN and zzTRACEOUT.
	      The only argument is a char * pointing to a C-style string  which  is  the  grammar
	      rule recognized by the current parsing function.	If no definition is given for the
	      trace functions, upon rule entry and exit, a message  will  be  printed  indicating
	      that a particular rule as been entered or exited.

       -ge    Generate an error class for each non-terminal.

       -gh    Generate	stdpccts.h  for non-ANTLR-generated files to include.  This file contains
	      all defines needed to describe the type of parser generated by antlr (e.g. how much
	      lookahead is used and whether or not trees are constructed) and contains the header
	      action specified by the user.

       -gk    Generate parsers that delay lookahead fetches until needed.  Without  this  option,
	      antlr generates parsers which always have k tokens of lookahead available.

       -gl    Generate	line  info  about  grammar  actions in C parser of the form # line "file"
	      which makes error messages from the C/C++ compiler make more  sense  as  they  will
	      point into the grammar file not the resulting C file.  Debugging is easier as well,
	      because you will step through the grammar not C file.

       -gs    Do not generate sets for token expression lists; instead	generate  a  ||-separated
	      sequence of LA(1)==token_number.	The default is to generate sets.

       -gt    Generate code for Abstract-Syntax Trees.

       -gx    Do  not  create  the  lexical  analyzer files (dlg-related).  This option should be
	      given when the user wishes to provide a customized lexical analyzer.  It	may  also
	      be  used	in  make scripts to cause only the parser to be rebuilt when a change not
	      affecting the lexical structure is made to the input grammars.

       -k n   Set k of LL(k) to n; i.e. set tokens of look-ahead (default==1).

       -o dir Directory where output files should go (default=".").  This is very nice for  keep-
	      ing the source directory clear of ANTLR and DLG spawn.

       -p     The  complete  grammar,  collected from all input grammar files and stripped of all
	      comments and embedded actions, is listed to stdout.  This is  intended  to  aid  in
	      viewing  the  entire  grammar  as a whole and to eliminate the need to keep actions
	      concisely stated so that the grammar is easier to read.  Hence, it is preferable to
	      embed  even  complex  actions  directly in the grammar, rather than to call them as
	      subroutines, since the subroutine call overhead will be saved.

       -pa    This option is the same as -p except that the output is annotated  with  the  first
	      sets determined from grammar analysis.

       -prc on
	      Turn on the computation and hoisting of predicate context.

       -prc off
	      Turn off the computation and hoisting of predicate context.  This option makes 1.10
	      behave like the 1.06 release with option -pr on.	Context  computation  is  off  by
	      default.

       -rl n  Limit  the  maximum  number of tree nodes used by grammar analysis to n.	Occasion-
	      ally, antlr is unable to analyze a grammar submitted by the user.  This rare situa-
	      tion  can  only  occur  when  the  grammar  is large and the amount of lookahead is
	      greater than one.  A nonlinear analysis algorithm is used by PCCTS  to  handle  the
	      general  case  of  LL(k)	parsing.  The average complexity of analysis, however, is
	      near linear due to some fancy footwork in the implementation which reduces the num-
	      ber  of  calls to the full LL(k) algorithm.  An error message will be displayed, if
	      this limit is reached, which indicates the grammar construct  being  analyzed  when
	      antlr  hit  a non-linearity.  Use this option if antlr seems to go out to lunch and
	      your disk start thrashing; try n=10000 to start.	Once the offending construct  has
	      been identified, try to remove the ambiguity that antlr was trying to overcome with
	      large lookahead analysis.  The introduction of (...)?  backtracking  blocks  elimi-
	      nates some of these problems -- antlr does not analyze alternatives that begin with
	      (...)? (it simply backtracks, if necessary, at run time).

       -w1    Set low warning level.  Do not warn if semantic predicates and/or (...)? blocks are
	      assumed to cover ambiguous alternatives.

       -w2    Ambiguous  parsing  decisions  yield warnings even if semantic predicates or (...)?
	      blocks are used.	Warn if predicate context computed and semantic predicates incom-
	      pletely disambiguate alternative productions.

       -      Read grammar from standard input and generate stdin.c as the parser file.

SPECIAL CONSIDERATIONS
       Antlr  works...	 we  think.   There  is no implicit guarantee of anything.  We reserve no
       legal rights to the software known as the Purdue Compiler Construction Tool Set (PCCTS) --
       PCCTS  is  in  the public domain.  An individual or company may do whatever they wish with
       source code distributed with PCCTS or the code generated by PCCTS, including the  incorpo-
       ration  of  PCCTS, or its output, into commercial software.  We encourage users to develop
       software with PCCTS.  However, we do ask that credit is given to us for developing  PCCTS.
       By  "credit",  we  mean	that if you incorporate our source code into one of your programs
       (commercial product, research project, or otherwise) that you acknowledge this fact  some-
       where  in the documentation, research report, etc...  If you like PCCTS and have developed
       a nice tool with the output, please mention that you developed it using PCCTS.  As long as
       these  guidelines  are followed, we expect to continue enhancing this system and expect to
       make other tools available as they are completed.

FILES
       *.c    output C parser.

       *.cpp  output C++ parser when C++ mode is used.

       parser.dlg
	      output dlg lexical analyzer.

       err.c  token string array, error sets and error support routines.  Not used in C++ mode.

       remap.h
	      file that redefines all globally visible parser symbols.	The use  of  the  #parser
	      directive creates this file.  Not used in C++ mode.

       stdpccts.h
	      list of definitions needed by C files, not generated by PCCTS, that reference PCCTS
	      objects.	This is not generated by default.  Not used in C++ mode.

       tokens.h
	      output #defines for tokens used and function prototypes for functions generated for
	      rules.

SEE ALSO
       dlg(1), pccts(1)

ANTLR					  September 1995				 ANTLR(1)


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