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ANTLR(1) PCCTS Manual Pages ANTLR(1)
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antlr - ANother Tool for Language Recognition
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antlr [_o_p_t_i_o_n_s] _g_r_a_m_m_a_r__f_i_l_e_s
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_A_n_t_l_r converts an extended form of context-free grammar into
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a set of C functions which directly implement an efficient
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form of deterministic recursive-descent LL(k) parser.
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Context-free grammars may be augmented with predicates to
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allow semantics to influence parsing; this allows a form of
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context-sensitive parsing. Selective backtracking is also
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available to handle non-LL(k) and even non-LALR(k) con-
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structs. _A_n_t_l_r also produces a definition of a lexer which
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can be automatically converted into C code for a DFA-based
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lexer by _d_l_g. Hence, _a_n_t_l_r serves a function much like that
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of _y_a_c_c, however, it is notably more flexible and is more
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integrated with a lexer generator (_a_n_t_l_r directly generates
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_d_l_g code, whereas _y_a_c_c and _l_e_x are given independent
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descriptions). Unlike _y_a_c_c which accepts LALR(1) grammars,
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_a_n_t_l_r accepts LL(k) grammars in an extended BNF notation -
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which eliminates the need for precedence rules.
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Like _y_a_c_c grammars, _a_n_t_l_r grammars can use automatically-
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maintained symbol attribute values referenced as dollar
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variables. Further, because _a_n_t_l_r generates top-down
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parsers, arbitrary values may be inherited from parent rules
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(passed like function parameters). _A_n_t_l_r also has a mechan-
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ism for creating and manipulating abstract-syntax-trees.
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There are various other niceties in _a_n_t_l_r, including the
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ability to spread one grammar over multiple files or even
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multiple grammars in a single file, the ability to generate
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a version of the grammar with actions stripped out (for
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documentation purposes), and lots more.
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Use up to _n symbols of lookahead when using compressed
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(linear approximation) lookahead. This type of looka-
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head is very cheap to compute and is attempted before
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full LL(k) lookahead, which is of exponential complex-
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ity in the worst case. In general, the compressed loo-
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kahead can be much deeper (e.g, -ck 10) _t_h_a_n _t_h_e _f_u_l_l
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_l_o_o_k_a_h_e_a_d (_w_h_i_c_h _u_s_u_a_l_l_y _m_u_s_t _b_e _l_e_s_s _t_h_a_n _4).
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-CC Generate C++ output from both ANTLR and DLG.
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-cr Generate a cross-reference for all rules. For each
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rule, print a list of all other rules that reference
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-e1 Ambiguities/errors shown in low detail (default).
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-e2 Ambiguities/errors shown in more detail.
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-e3 Ambiguities/errors shown in excruciating detail.
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Rename stdpccts.h header (turns on -gh) to file.
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Rename lexical output, parser.dlg, to file.
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Rename file with lexical mode definitions, mode.h, to
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Rename file which remaps globally visible symbols,
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Rename tokens.h to file.
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-ga Generate ANSI-compatible code (default case). This has
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not been rigorously tested to be ANSI XJ11 C compliant,
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but it is close. The normal output of _a_n_t_l_r is
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currently compilable under both K&R, ANSI C, and C++-
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this option does nothing because _a_n_t_l_r generates a
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bunch of #ifdef's to do the right thing depending on
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-gc Indicates that _a_n_t_l_r should generate no C code, i.e.,
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only perform analysis on the grammar.
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-gd C code is inserted in each of the _a_n_t_l_r generated pars-
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ing functions to provide for user-defined handling of a
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detailed parse trace. The inserted code consists of
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calls to the user-supplied macros or functions called
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zzTRACEIN and zzTRACEOUT. The only argument is a _c_h_a_r
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* pointing to a C-style string which is the grammar
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rule recognized by the current parsing function. If no
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definition is given for the trace functions, upon rule
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entry and exit, a message will be printed indicating
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that a particular rule as been entered or exited.
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-ge Generate an error class for each non-terminal.
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-gh Generate stdpccts.h for non-ANTLR-generated files to
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include. This file contains all defines needed to
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describe the type of parser generated by _a_n_t_l_r (e.g.
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how much lookahead is used and whether or not trees are
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constructed) and contains the header action specified
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-gk Generate parsers that delay lookahead fetches until
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needed. Without this option, _a_n_t_l_r generates parsers
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which always have _k tokens of lookahead available.
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-gl Generate line info about grammar actions in C parser of
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the form # _l_i_n_e "_f_i_l_e" which makes error messages from
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the C/C++ compiler make more sense as they will point
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into the grammar file not the resulting C file.
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Debugging is easier as well, because you will step
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through the grammar not C file.
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-gs Do not generate sets for token expression lists;
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instead generate a ||-separated sequence of
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LA(1)==_t_o_k_e_n__n_u_m_b_e_r. The default is to generate sets.
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-gt Generate code for Abstract-Syntax Trees.
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-gx Do not create the lexical analyzer files (dlg-related).
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This option should be given when the user wishes to
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provide a customized lexical analyzer. It may also be
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used in _m_a_k_e scripts to cause only the parser to be
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rebuilt when a change not affecting the lexical struc-
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ture is made to the input grammars.
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-k _n Set k of LL(k) to _n; i.e. set tokens of look-ahead
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Directory where output files should go (default=".").
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This is very nice for keeping the source directory
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clear of ANTLR and DLG spawn.
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-p The complete grammar, collected from all input grammar
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files and stripped of all comments and embedded
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actions, is listed to stdout. This is intended to aid
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in viewing the entire grammar as a whole and to elim-
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inate the need to keep actions concisely stated so that
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the grammar is easier to read. Hence, it is preferable
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to embed even complex actions directly in the grammar,
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rather than to call them as subroutines, since the sub-
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routine call overhead will be saved.
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-pa This option is the same as -p except that the output is
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annotated with the first sets determined from grammar
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Turn on the computation and hoisting of predicate con-
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Turn off the computation and hoisting of predicate con-
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text. This option makes 1.10 behave like the 1.06
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release with option -pr on. Context computation is off
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Limit the maximum number of tree nodes used by grammar
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analysis to _n. Occasionally, _a_n_t_l_r is unable to
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analyze a grammar submitted by the user. This rare
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situation can only occur when the grammar is large and
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the amount of lookahead is greater than one. A non-
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linear analysis algorithm is used by PCCTS to handle
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the general case of LL(k) parsing. The average com-
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plexity of analysis, however, is near linear due to
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some fancy footwork in the implementation which reduces
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the number of calls to the full LL(k) algorithm. An
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error message will be displayed, if this limit is
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reached, which indicates the grammar construct being
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analyzed when _a_n_t_l_r hit a non-linearity. Use this
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option if _a_n_t_l_r seems to go out to lunch and your disk
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start thrashing; try _n=10000 to start. Once the
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offending construct has been identified, try to remove
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the ambiguity that _a_n_t_l_r was trying to overcome with
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large lookahead analysis. The introduction of (...)?
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backtracking blocks eliminates some of these problems -
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_a_n_t_l_r does not analyze alternatives that begin with
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(...)? (it simply backtracks, if necessary, at run
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-w1 Set low warning level. Do not warn if semantic
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predicates and/or (...)? blocks are assumed to cover
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ambiguous alternatives.
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-w2 Ambiguous parsing decisions yield warnings even if
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semantic predicates or (...)? blocks are used. Warn if
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predicate context computed and semantic predicates
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incompletely disambiguate alternative productions.
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- Read grammar from standard input and generate stdin.c
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SPECIAL CONSIDERATIONS
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_A_n_t_l_r works... we think. There is no implicit guarantee of
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anything. We reserve no legal rights to the software known
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as the Purdue Compiler Construction Tool Set (PCCTS) - PCCTS
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is in the public domain. An individual or company may do
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whatever they wish with source code distributed with PCCTS
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or the code generated by PCCTS, including the incorporation
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of PCCTS, or its output, into commercial software. We
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encourage users to develop software with PCCTS. However, we
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do ask that credit is given to us for developing PCCTS. By
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"credit", we mean that if you incorporate our source code
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into one of your programs (commercial product, research pro-
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ject, or otherwise) that you acknowledge this fact somewhere
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in the documentation, research report, etc... If you like
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PCCTS and have developed a nice tool with the output, please
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mention that you developed it using PCCTS. As long as these
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guidelines are followed, we expect to continue enhancing
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this system and expect to make other tools available as they
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output C++ parser when C++ mode is used.
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output _d_l_g lexical analyzer.
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token string array, error sets and error support rou-
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tines. Not used in C++ mode.
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file that redefines all globally visible parser sym-
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bols. The use of the #parser directive creates this
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file. Not used in C++ mode.
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list of definitions needed by C files, not generated by
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PCCTS, that reference PCCTS objects. This is not gen-
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erated by default. Not used in C++ mode.
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output #_d_e_f_i_n_e_s for tokens used and function prototypes
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for functions generated for rules.
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pccts/antlr/antlr1.txt
