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ANTLR(1) PCCTS Manual Pages ANTLR(1)
NAME
antlr - ANother Tool for Language Recognition
SYNTAX
antlr [_o_p_t_i_o_n_s] _g_r_a_m_m_a_r__f_i_l_e_s
DESCRIPTION
_A_n_t_l_r 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) con-
structs. _A_n_t_l_r also produces a definition of a lexer which
can be automatically converted into C code for a DFA-based
lexer by _d_l_g. Hence, _a_n_t_l_r serves a function much like that
of _y_a_c_c, however, it is notably more flexible and is more
integrated with a lexer generator (_a_n_t_l_r directly generates
_d_l_g code, whereas _y_a_c_c and _l_e_x are given independent
descriptions). Unlike _y_a_c_c which accepts LALR(1) grammars,
_a_n_t_l_r accepts LL(k) grammars in an extended BNF notation -
which eliminates the need for precedence rules.
Like _y_a_c_c grammars, _a_n_t_l_r grammars can use automatically-
maintained symbol attribute values referenced as dollar
variables. Further, because _a_n_t_l_r generates top-down
parsers, arbitrary values may be inherited from parent rules
(passed like function parameters). _A_n_t_l_r also has a mechan-
ism for creating and manipulating abstract-syntax-trees.
There are various other niceties in _a_n_t_l_r, 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 looka-
head is very cheap to compute and is attempted before
full LL(k) lookahead, which is of exponential complex-
ity in the worst case. In general, the compressed loo-
kahead can be much deeper (e.g, -ck 10) _t_h_a_n _t_h_e _f_u_l_l
_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).
-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 _a_n_t_l_r is
currently compilable under both K&R, ANSI C, and C++-
this option does nothing because _a_n_t_l_r generates a
bunch of #ifdef's to do the right thing depending on
the language.
-gc Indicates that _a_n_t_l_r should generate no C code, i.e.,
only perform analysis on the grammar.
-gd C code is inserted in each of the _a_n_t_l_r generated pars-
ing 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 _c_h_a_r
* 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 _a_n_t_l_r (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, _a_n_t_l_r generates parsers
which always have _k tokens of lookahead available.
-gl Generate line info about grammar actions in C parser of
the form # _l_i_n_e "_f_i_l_e" 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)==_t_o_k_e_n__n_u_m_b_e_r. 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 _m_a_k_e scripts to cause only the parser to be
rebuilt when a change not affecting the lexical struc-
ture 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 elim-
inate 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 sub-
routine 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 con-
text.
-prc off
Turn off the computation and hoisting of predicate con-
text. 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, _a_n_t_l_r 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 non-
linear analysis algorithm is used by PCCTS to handle
the general case of LL(k) parsing. The average com-
plexity 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 _a_n_t_l_r hit a non-linearity. Use this
option if _a_n_t_l_r 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 _a_n_t_l_r was trying to overcome with
large lookahead analysis. The introduction of (...)?
backtracking blocks eliminates some of these problems -
_a_n_t_l_r 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
_A_n_t_l_r 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 pro-
ject, 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 _d_l_g lexical analyzer.
err.c
token string array, error sets and error support rou-
tines. Not used in C++ mode.
remap.h
file that redefines all globally visible parser sym-
bols. 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 gen-
erated by default. Not used in C++ mode.
tokens.h
output #_d_e_f_i_n_e_s for tokens used and function prototypes
for functions generated for rules.
SEE ALSO
dlg(1), pccts(1)
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