xenial (1) antlr.1.gz

Provided by: pccts_1.33MR33-6_amd64 bug

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 definition 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 eliminates the need for precedence
       rules.

       Like yacc grammars, antlr grammars can use automatically-maintained symbol attribute values 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 currently 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 language.

       -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 keeping 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.   Occasionally,  antlr  is
              unable  to  analyze  a grammar submitted by the user.  This rare situation 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  number
              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
              eliminates 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 incompletely 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 incorporation 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  somewhere  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)