<p>The language parser code created by Lemon is very robust and
is well-suited for use in internet-facing applications that need to
-safely process maliciously crafted inputs.
+safely process maliciously crafted inputs.</p>
<p>The "lemon.exe" command-line tool itself works great when given a valid
input grammar file and almost always gives helpful
<p>The main goal of Lemon is to translate a context free grammar (CFG)
for a particular language into C code that implements a parser for
that language.
-The program has two inputs:
+The program has two inputs:</p>
<ul>
<li>The grammar specification.
<li>A parser template file.
</ul>
-Typically, only the grammar specification is supplied by the programmer.
+<p>Typically, only the grammar specification is supplied by the programmer.
Lemon comes with a default parser template which works fine for most
applications. But the user is free to substitute a different parser
template if desired.</p>
<p>Depending on command-line options, Lemon will generate up to
-three output files.
+three output files.</p>
<ul>
<li>C code to implement the parser.
<li>A header file defining an integer ID for each terminal symbol.
<li>An information file that describes the states of the generated parser
automaton.
</ul>
-By default, all three of these output files are generated.
+<p>By default, all three of these output files are generated.
The header file is suppressed if the "-m" command-line option is
used and the report file is omitted when "-q" is selected.</p>
<p>The grammar specification file uses a ".y" suffix, by convention.
In the examples used in this document, we'll assume the name of the
grammar file is "gram.y". A typical use of Lemon would be the
-following command:
+following command:</p>
<pre>
lemon gram.y
</pre>
-This command will generate three output files named "gram.c",
+<p>This command will generate three output files named "gram.c",
"gram.h" and "gram.out".
The first is C code to implement the parser. The second
is the header file that defines numerical values for all
<p>The behavior of Lemon can be modified using command-line options.
You can obtain a list of the available command-line options together
-with a brief explanation of what each does by typing
+with a brief explanation of what each does by typing</p>
<pre>
lemon "-?"
</pre>
-As of this writing, the following command-line options are supported:
+<p>As of this writing, the following command-line options are supported:</p>
<ul>
<li><b>-b</b>
Show only the basis for each parser state in the report file.
<p>Before a program begins using a Lemon-generated parser, the program
must first create the parser.
-A new parser is created as follows:
+A new parser is created as follows:</p>
<pre>
void *pParser = ParseAlloc( malloc );
</pre>
-The ParseAlloc() routine allocates and initializes a new parser and
+<p>The ParseAlloc() routine allocates and initializes a new parser and
returns a pointer to it.
The actual data structure used to represent a parser is opaque —
its internal structure is not visible or usable by the calling routine.
subroutine used to allocate memory. Typically this means malloc().</p>
<p>After a program is finished using a parser, it can reclaim all
-memory allocated by that parser by calling
+memory allocated by that parser by calling</p>
<pre>
ParseFree(pParser, free);
</pre>
-The first argument is the same pointer returned by ParseAlloc(). The
+<p>The first argument is the same pointer returned by ParseAlloc(). The
second argument is a pointer to the function used to release bulk
memory back to the system.</p>
<p>After a parser has been allocated using ParseAlloc(), the programmer
must supply the parser with a sequence of tokens (terminal symbols) to
be parsed. This is accomplished by calling the following function
-once for each token:
+once for each token:<p>
<pre>
Parse(pParser, hTokenID, sTokenData, pArg);
</pre>
-The first argument to the Parse() routine is the pointer returned by
+<p>The first argument to the Parse() routine is the pointer returned by
ParseAlloc().
The second argument is a small positive integer that tells the parser the
type of the next token in the data stream.
to the action routines without having to use global variables.</p>
<p>A typical use of a Lemon parser might look something like the
-following:
+following:</p>
<pre>
1 ParseTree *ParseFile(const char *zFilename){
2 Tokenizer *pTokenizer;
17 return sState.treeRoot;
18 }
</pre>
-This example shows a user-written routine that parses a file of
+<p>This example shows a user-written routine that parses a file of
text and returns a pointer to the parse tree.
(All error-handling code is omitted from this example to keep it
simple.)
some kind of structure that contains details about each token,
such as its complete text, what line it occurs on, etc.</p>
-<p>This example also assumes the existence of structure of type
+<p>This example also assumes the existence of a structure of type
ParserState that holds state information about a particular parse.
An instance of such a structure is created on line 6 and initialized
on line 10. A pointer to this structure is passed into the Parse()
the ParserState structure is left pointing to the root of the parse
tree.</p>
-<p>The core of this example as it relates to Lemon is as follows:
+<p>The core of this example as it relates to Lemon is as follows:</p>
<pre>
ParseFile(){
pParser = ParseAlloc( malloc );
ParseFree(pParser, free );
}
</pre>
-Basically, what a program has to do to use a Lemon-generated parser
+<p>Basically, what a program has to do to use a Lemon-generated parser
is first create the parser, then send it lots of tokens obtained by
tokenizing an input source. When the end of input is reached, the
Parse() routine should be called one last time with a token type
<p>There is one other interface routine that should be mentioned
before we move on.
The ParseTrace() function can be used to generate debugging output
-from the parser. A prototype for this routine is as follows:
+from the parser. A prototype for this routine is as follows:</p>
<pre>
ParseTrace(FILE *stream, char *zPrefix);
</pre>
-After this routine is called, a short (one-line) message is written
+<p>After this routine is called, a short (one-line) message is written
to the designated output stream every time the parser changes states
or calls an action routine. Each such message is prefaced using
the text given by zPrefix. This debugging output can be turned off
<p>Programmers who have previously used the yacc or bison parser
generator will notice several important differences between yacc and/or
-bison and Lemon.
+bison and Lemon.</p>
<ul>
<li>In yacc and bison, the parser calls the tokenizer. In Lemon,
the tokenizer calls the parser.
<li>Lemon allows multiple parsers to be running simultaneously. Yacc
and bison do not.
</ul>
-These differences may cause some initial confusion for programmers
+<p>These differences may cause some initial confusion for programmers
with prior yacc and bison experience.
But after years of experience using Lemon, I firmly
believe that the Lemon way of doing things is better.</p>
Most of the work in using Lemon is in writing an appropriate
grammar file.</p>
-<p>The grammar file for Lemon is, for the most part, free format.
+<p>The grammar file for Lemon is, for the most part, a free format.
It does not have sections or divisions like yacc or bison. Any
-declaration can occur at any point in the file.
-Lemon ignores whitespace (except where it is needed to separate
-tokens), and it honors the same commenting conventions as C and C++.</p>
+declaration can occur at any point in the file. Lemon ignores
+whitespace (except where it is needed to separate tokens), and it
+honors the same commenting conventions as C and C++.</p>
<h3>Terminals and Nonterminals</h3>
first rule is assumed to be the start symbol for the grammar (unless
specified otherwise using the <tt><a href='#start_symbol'>%start_symbol</a></tt>
directive described below.)
-A typical sequence of grammar rules might look something like this:
+A typical sequence of grammar rules might look something like this:</p>
<pre>
expr ::= expr PLUS expr.
expr ::= expr TIMES expr.
expr ::= LPAREN expr RPAREN.
expr ::= VALUE.
</pre>
-</p>
<p>There is one non-terminal in this example, "expr", and five
terminal symbols or tokens: "PLUS", "TIMES", "LPAREN",
In Lemon, this action is specified by putting the C code (contained
within curly braces <tt>{...}</tt>) immediately after the
period that closes the rule.
-For example:
+For example:</p>
<pre>
expr ::= expr PLUS expr. { printf("Doing an addition...\n"); }
</pre>
-</p>
<p>In order to be useful, grammar actions must normally be linked to
their associated grammar rules.
<p>Lemon avoids the need to count grammar symbols by assigning symbolic
names to each symbol in a grammar rule and then using those symbolic
names in the action.
-In yacc or bison, one would write this:
+In yacc or bison, one would write this:</p>
<pre>
expr -> expr PLUS expr { $$ = $1 + $3; };
</pre>
-But in Lemon, the same rule becomes the following:
+<p>But in Lemon, the same rule becomes the following:</p>
<pre>
expr(A) ::= expr(B) PLUS expr(C). { A = B+C; }
</pre>
-In the Lemon rule, any symbol in parentheses after a grammar rule
+<p>In the Lemon rule, any symbol in parentheses after a grammar rule
symbol becomes a place holder for that symbol in the grammar rule.
This place holder can then be used in the associated C action to
-stand for the value of that symbol.<p>
+stand for the value of that symbol.</p>
<p>The Lemon notation for linking a grammar rule with its reduce
action is superior to yacc/bison on several counts.
includes a linking symbol in parentheses but that linking symbol
is not actually used in the reduce action, then an error message
is generated.
-For example, the rule
+For example, the rule</p>
<pre>
expr(A) ::= expr(B) PLUS expr(C). { A = B; }
</pre>
-will generate an error because the linking symbol "C" is used
+<p>will generate an error because the linking symbol "C" is used
in the grammar rule but not in the reduce action.</p>
<p>The Lemon notation for linking grammar rules to reduce actions
allocated by the values of terminals and nonterminals on the
right-hand side of a rule.</p>
-<a name='precrules'></a>
+<a id='precrules'></a>
<h3>Precedence Rules</h3>
<p>Lemon resolves parsing ambiguities in exactly the same way as
mentioned in earlier directives have a lower precedence than
terminal symbols mentioned in later directives. For example:</p>
-<p><pre>
+<pre>
%left AND.
%left OR.
%nonassoc EQ NE GT GE LT LE.
%left PLUS MINUS.
%left TIMES DIVIDE MOD.
%right EXP NOT.
-</pre></p>
+</pre>
<p>In the preceding sequence of directives, the AND operator is
defined to have the lowest precedence. The OR operator is one
precedence level higher. And so forth. Hence, the grammar would
-attempt to group the ambiguous expression
+attempt to group the ambiguous expression</p>
<pre>
a AND b OR c
</pre>
-like this
+<p>like this</p>
<pre>
a AND (b OR c).
</pre>
-The associativity (left, right or nonassoc) is used to determine
+<p>The associativity (left, right or nonassoc) is used to determine
the grouping when the precedence is the same. AND is left-associative
-in our example, so
+in our example, so</p>
<pre>
a AND b AND c
</pre>
-is parsed like this
+<p>is parsed like this</p>
<pre>
(a AND b) AND c.
</pre>
-The EXP operator is right-associative, though, so
+<p>The EXP operator is right-associative, though, so</p>
<pre>
a EXP b EXP c
</pre>
-is parsed like this
+<p>is parsed like this</p>
<pre>
a EXP (b EXP c).
</pre>
-The nonassoc precedence is used for non-associative operators.
-So
+<p>The nonassoc precedence is used for non-associative operators.
+So</p>
<pre>
a EQ b EQ c
</pre>
-is an error.</p>
+<p>is an error.</p>
<p>The precedence of non-terminals is transferred to rules as follows:
The precedence of a grammar rule is equal to the precedence of the
symbol in square braces after the period at the end of the rule and
before any C-code. For example:</p>
-<p><pre>
+<pre>
expr = MINUS expr. [NOT]
-</pre></p>
+</pre>
<p>This rule has a precedence equal to that of the NOT symbol, not the
MINUS symbol as would have been the case by default.</p>
symbols and individual
grammar rules, we can now explain precisely how parsing conflicts
are resolved in Lemon. Shift-reduce conflicts are resolved
-as follows:
+as follows:</p>
<ul>
<li> If either the token to be shifted or the rule to be reduced
lacks precedence information, then resolve in favor of the
<li> Otherwise, resolve the conflict by doing the shift, and
report a parsing conflict.
</ul>
-Reduce-reduce conflicts are resolved this way:
+<p>Reduce-reduce conflicts are resolved this way:</p>
<ul>
<li> If either reduce rule
lacks precedence information, then resolve in favor of the
directives used to assign precedence to terminals is important, but
other than that, the order of directives in Lemon is arbitrary.</p>
-<p>Lemon supports the following special directives:
+<p>Lemon supports the following special directives:</p>
<ul>
<li><tt><a href='#pcode'>%code</a></tt>
<li><tt><a href='#default_destructor'>%default_destructor</a></tt>
<li><tt><a href='#ptype'>%type</a></tt>
<li><tt><a href='#pwildcard'>%wildcard</a></tt>
</ul>
-Each of these directives will be described separately in the
+<p>Each of these directives will be described separately in the
following sections:</p>
-<a name='pcode'></a>
+<a id='pcode'></a>
<h4>The <tt>%code</tt> directive</h4>
<p>The <tt>%code</tt> directive is used to specify additional C code that
a tokenizer or even the "main()" function
as part of the output file.</p>
-<a name='default_destructor'></a>
+<a id='default_destructor'></a>
<h4>The <tt>%default_destructor</tt> directive</h4>
<p>The <tt>%default_destructor</tt> directive specifies a destructor to
use for non-terminals that do not have their own destructor
specified by a separate <tt>%destructor</tt> directive. See the documentation
-on the <tt><a name='#destructor'>%destructor</a></tt> directive below for
+on the <tt><a href='#destructor'>%destructor</a></tt> directive below for
additional information.</p>
<p>In some grammars, many different non-terminal symbols have the
a convenient way to specify the same destructor for all those
non-terminals using a single statement.</p>
-<a name='default_type'></a>
+<a id='default_type'></a>
<h4>The <tt>%default_type</tt> directive</h4>
<p>The <tt>%default_type</tt> directive specifies the data type of non-terminal
symbols that do not have their own data type defined using a separate
<tt><a href='#ptype'>%type</a></tt> directive.</p>
-<a name='destructor'></a>
+<a id='destructor'></a>
<h4>The <tt>%destructor</tt> directive</h4>
<p>The <tt>%destructor</tt> directive is used to specify a destructor for
<p>A non-terminal's destructor is called to dispose of the
non-terminal's value whenever the non-terminal is popped from
-the stack. This includes all of the following circumstances:
+the stack. This includes all of the following circumstances:</p>
<ul>
<li> When a rule reduces and the value of a non-terminal on
the right-hand side is not linked to C code.
<li> When the stack is popped during error processing.
<li> When the ParseFree() function runs.
</ul>
-The destructor can do whatever it wants with the value of
+<p>The destructor can do whatever it wants with the value of
the non-terminal, but its design is to deallocate memory
or other resources held by that non-terminal.</p>
-<p>Consider an example:
+<p>Consider an example:</p>
<pre>
%type nt {void*}
%destructor nt { free($$); }
nt(A) ::= ID NUM. { A = malloc( 100 ); }
</pre>
-This example is a bit contrived, but it serves to illustrate how
+<p>This example is a bit contrived, but it serves to illustrate how
destructors work. The example shows a non-terminal named
"nt" that holds values of type "void*". When the rule for
an "nt" reduces, it sets the value of the non-terminal to
allocated objects when they go out of scope.
To do the same using yacc or bison is much more difficult.</p>
-<a name='extraarg'></a>
+<a id='extraarg'></a>
<h4>The <tt>%extra_argument</tt> directive</h4>
-The <tt>%extra_argument</tt> directive instructs Lemon to add a 4th parameter
+<p>The <tt>%extra_argument</tt> directive instructs Lemon to add a 4th parameter
to the parameter list of the Parse() function it generates. Lemon
doesn't do anything itself with this extra argument, but it does
make the argument available to C-code action routines, destructors,
and so forth. For example, if the grammar file contains:</p>
-<p><pre>
+<pre>
%extra_argument { MyStruct *pAbc }
-</pre></p>
+</pre>
<p>Then the Parse() function generated will have an 4th parameter
of type "MyStruct*" and all action routines will have access to
<p>The <tt>%extra_context</tt> directive works the same except that it
is passed in on the ParseAlloc() or ParseInit() routines instead of
-on Parse().
+on Parse().</p>
-<a name='extractx'></a>
+<a id='extractx'></a>
<h4>The <tt>%extra_context</tt> directive</h4>
-The <tt>%extra_context</tt> directive instructs Lemon to add a 2nd parameter
-to the parameter list of the ParseAlloc() and ParseInif() functions. Lemon
+<p>The <tt>%extra_context</tt> directive instructs Lemon to add a 2nd parameter
+to the parameter list of the ParseAlloc() and ParseInit() functions. Lemon
doesn't do anything itself with these extra argument, but it does
store the value make it available to C-code action routines, destructors,
and so forth. For example, if the grammar file contains:</p>
-<p><pre>
+<pre>
%extra_context { MyStruct *pAbc }
-</pre></p>
+</pre>
<p>Then the ParseAlloc() and ParseInit() functions will have an 2nd parameter
of type "MyStruct*" and all action routines will have access to
a variable named "pAbc" that is the value of that 2nd parameter.</p>
<p>The <tt>%extra_argument</tt> directive works the same except that it
-is passed in on the Parse() routine instead of on ParseAlloc()/ParseInit().
+is passed in on the Parse() routine instead of on ParseAlloc()/ParseInit().</p>
-<a name='pfallback'></a>
+<a id='pfallback'></a>
<h4>The <tt>%fallback</tt> directive</h4>
<p>The <tt>%fallback</tt> directive specifies an alternative meaning for one
provides a mechanism to tell the parser: "If you are unable to parse
this keyword, try treating it as an identifier instead."</p>
-<p>The syntax of <tt>%fallback</tt> is as follows:
+<p>The syntax of <tt>%fallback</tt> is as follows:</p>
<blockquote>
<tt>%fallback</tt> <i>ID</i> <i>TOKEN...</i> <b>.</b>
arguments are tokens which fall back to the token identified by the first
argument.</p>
-<a name='pifdef'></a>
+<a id='pifdef'></a>
<h4>The <tt>%if</tt> directive and its friends</h4>
<p>The <tt>%if</tt>, <tt>%ifdef</tt>, <tt>%ifndef</tt>, <tt>%else</tt>,
intended to be a single preprocessor symbol name, not a general expression.
Use the "<tt>%if</tt>" directive for general expressions.</p>
-<a name='pinclude'></a>
+<a id='pinclude'></a>
<h4>The <tt>%include</tt> directive</h4>
<p>The <tt>%include</tt> directive specifies C code that is included at the
preprocessor statements at the beginning of the generated parser.
For example:</p>
-<p><pre>
+<pre>
%include {#include <unistd.h>}
-</pre></p>
+</pre>
<p>This might be needed, for example, if some of the C actions in the
grammar call functions that are prototyped in unistd.h.</p>
<p>Use the <tt><a href="#pcode">%code</a></tt> directive to add code to
the end of the generated parser.</p>
-<a name='pleft'></a>
+<a id='pleft'></a>
<h4>The <tt>%left</tt> directive</h4>
The <tt>%left</tt> directive is used (along with the
given the same left-associative precedence value. Subsequent
<tt>%left</tt> directives have higher precedence. For example:</p>
-<p><pre>
+<pre>
%left AND.
%left OR.
%nonassoc EQ NE GT GE LT LE.
%left PLUS MINUS.
%left TIMES DIVIDE MOD.
%right EXP NOT.
-</pre></p>
+</pre>
<p>Note the period that terminates each <tt>%left</tt>,
<tt>%right</tt> or <tt>%nonassoc</tt>
operators. For this reason, it is recommended that you use <tt>%left</tt>
rather than <tt>%right</tt> whenever possible.</p>
-<a name='pname'></a>
+<a id='pname'></a>
<h4>The <tt>%name</tt> directive</h4>
<p>By default, the functions generated by Lemon all begin with the
five-character string "Parse". You can change this string to something
different using the <tt>%name</tt> directive. For instance:</p>
-<p><pre>
+<pre>
%name Abcde
-</pre></p>
+</pre>
<p>Putting this directive in the grammar file will cause Lemon to generate
-functions named
+functions named</p>
<ul>
<li> AbcdeAlloc(),
<li> AbcdeFree(),
<li> AbcdeTrace(), and
<li> Abcde().
</ul>
-The <tt>%name</tt> directive allows you to generate two or more different
+</p>The <tt>%name</tt> directive allows you to generate two or more different
parsers and link them all into the same executable.</p>
-<a name='pnonassoc'></a>
+<a id='pnonassoc'></a>
<h4>The <tt>%nonassoc</tt> directive</h4>
<p>This directive is used to assign non-associative precedence to
or on the <tt><a href='#pleft'>%left</a></tt> directive
for additional information.</p>
-<a name='parse_accept'></a>
+<a id='parse_accept'></a>
<h4>The <tt>%parse_accept</tt> directive</h4>
<p>The <tt>%parse_accept</tt> directive specifies a block of C code that is
<p>For example:</p>
-<p><pre>
+<pre>
%parse_accept {
printf("parsing complete!\n");
}
-</pre></p>
+</pre>
-<a name='parse_failure'></a>
+<a id='parse_failure'></a>
<h4>The <tt>%parse_failure</tt> directive</h4>
<p>The <tt>%parse_failure</tt> directive specifies a block of C code that
error using is usual error recovery strategy. The routine is
only invoked when parsing is unable to continue.</p>
-<p><pre>
+<pre>
%parse_failure {
fprintf(stderr,"Giving up. Parser is hopelessly lost...\n");
}
-</pre></p>
+</pre>
-<a name='pright'></a>
+<a id='pright'></a>
<h4>The <tt>%right</tt> directive</h4>
<p>This directive is used to assign right-associative precedence to
<a href='#precrules'>precedence rules</a>
or on the <a href='#pleft'>%left</a> directive for additional information.</p>
-<a name='stack_overflow'></a>
+<a id='stack_overflow'></a>
<h4>The <tt>%stack_overflow</tt> directive</h4>
<p>The <tt>%stack_overflow</tt> directive specifies a block of C code that
this just prints an error message. After a stack overflow, the parser
will be unable to continue and must be reset.</p>
-<p><pre>
+<pre>
%stack_overflow {
fprintf(stderr,"Giving up. Parser stack overflow\n");
}
-</pre></p>
+</pre>
<p>You can help prevent parser stack overflows by avoiding the use
of right recursion and right-precedence operators in your grammar.
Use left recursion and and left-precedence operators instead to
encourage rules to reduce sooner and keep the stack size down.
-For example, do rules like this:
+For example, do rules like this:</p>
<pre>
list ::= list element. // left-recursion. Good!
list ::= .
</pre>
-Not like this:
+<p>Not like this:</p>
<pre>
list ::= element list. // right-recursion. Bad!
list ::= .
-</pre></p>
+</pre>
-<a name='stack_size'></a>
+<a id='stack_size'></a>
<h4>The <tt>%stack_size</tt> directive</h4>
<p>If stack overflow is a problem and you can't resolve the trouble
after the <tt>%stack_size</tt> directive and Lemon will generate a parse
with a stack of the requested size. The default value is 100.</p>
-<p><pre>
+<pre>
%stack_size 2000
-</pre></p>
+</pre>
-<a name='start_symbol'></a>
+<a id='start_symbol'></a>
<h4>The <tt>%start_symbol</tt> directive</h4>
<p>By default, the start symbol for the grammar that Lemon generates
can choose a different start symbol using the
<tt>%start_symbol</tt> directive.</p>
-<p><pre>
+<pre>
%start_symbol prog
-</pre></p>
+</pre>
-<a name='syntax_error'></a>
+<a id='syntax_error'></a>
<h4>The <tt>%syntax_error</tt> directive</h4>
<p>See <a href='#error_processing'>Error Processing</a>.</p>
-<a name='token_class'></a>
+<a id='token_class'></a>
<h4>The <tt>%token_class</tt> directive</h4>
<p>Undocumented. Appears to be related to the MULTITERMINAL concept.
<a href='http://sqlite.org/src/fdiff?v1=796930d5fc2036c7&v2=624b24c5dc048e09&sbs=0'>Implementation</a>.</p>
-<a name='token_destructor'></a>
+<a id='token_destructor'></a>
<h4>The <tt>%token_destructor</tt> directive</h4>
<p>The <tt>%destructor</tt> directive assigns a destructor to a non-terminal
The <tt>%token_destructor</tt> directive does the same thing
for all terminal symbols.</p>
-<p>Unlike non-terminal symbols which may each have a different data type
+<p>Unlike non-terminal symbols, which may each have a different data type
for their values, terminals all use the same data type (defined by
the <tt><a href='#token_type'>%token_type</a></tt> directive)
and so they use a common destructor.
Other than that, the token destructor works just like the non-terminal
destructors.</p>
-<a name='token_prefix'></a>
+<a id='token_prefix'></a>
<h4>The <tt>%token_prefix</tt> directive</h4>
<p>Lemon generates #defines that assign small integer constants
add a prefix specified by this directive
to each of the #defines it generates.</p>
-<p>So if the default output of Lemon looked like this:
+<p>So if the default output of Lemon looked like this:</p>
<pre>
#define AND 1
#define MINUS 2
#define OR 3
#define PLUS 4
</pre>
-You can insert a statement into the grammar like this:
+<p>You can insert a statement into the grammar like this:</p>
<pre>
%token_prefix TOKEN_
</pre>
-to cause Lemon to produce these symbols instead:
+<p>to cause Lemon to produce these symbols instead:</p>
<pre>
#define TOKEN_AND 1
#define TOKEN_MINUS 2
#define TOKEN_OR 3
#define TOKEN_PLUS 4
-</pre></p>
+</pre>
-<a name='token_type'></a><a name='ptype'></a>
+<a id='token_type'></a><a id='ptype'></a>
<h4>The <tt>%token_type</tt> and <tt>%type</tt> directives</h4>
<p>These directives are used to specify the data types for values
make the value of a terminal symbol be a pointer to some kind of
token structure. Like this:</p>
-<p><pre>
+<pre>
%token_type {Token*}
-</pre></p>
+</pre>
<p>If the data type of terminals is not specified, the default value
is "void*".</p>
structure that contains all information about that non-terminal.
For example:</p>
-<p><pre>
+<pre>
%type expr {Expr*}
-</pre></p>
+</pre>
<p>Each entry on the parser's stack is actually a union containing
instances of all data types for every non-terminal and terminal symbol.
entry parser stack will require 100K of heap space. If you are willing
and able to pay that price, fine. You just need to know.</p>
-<a name='pwildcard'></a>
+<a id='pwildcard'></a>
<h4>The <tt>%wildcard</tt> directive</h4>
<p>The <tt>%wildcard</tt> directive is followed by a single token name and a
the wildcard token and some other token, the other token is always used.
The wildcard token is only matched if there are no alternatives.</p>
-<a name='error_processing'></a>
+<a id='error_processing'></a>
<h3>Error Processing</h3>
<p>After extensive experimentation over several years, it has been
projects / thirdparty / sqlite.git / commitdiff
