Index: third_party/sqlite/src/doc/lemon.html |
diff --git a/third_party/sqlite/src/doc/lemon.html b/third_party/sqlite/src/doc/lemon.html |
index b16e35960ef9e44d390cbb4c7f7eafbc19160ae0..114526f372ca8b870eb5cf3d1d6fa8d38268c6b1 100644 |
--- a/third_party/sqlite/src/doc/lemon.html |
+++ b/third_party/sqlite/src/doc/lemon.html |
@@ -5,14 +5,17 @@ |
<body bgcolor=white> |
<h1 align=center>The Lemon Parser Generator</h1> |
-<p>Lemon is an LALR(1) parser generator for C or C++. |
-It does the same job as ``bison'' and ``yacc''. |
-But lemon is not another bison or yacc clone. It |
+<p>Lemon is an LALR(1) parser generator for C. |
+It does the same job as "bison" and "yacc". |
+But lemon is not a bison or yacc clone. Lemon |
uses a different grammar syntax which is designed to |
-reduce the number of coding errors. Lemon also uses a more |
-sophisticated parsing engine that is faster than yacc and |
-bison and which is both reentrant and thread-safe. |
-Furthermore, Lemon implements features that can be used |
+reduce the number of coding errors. Lemon also uses a |
+parsing engine that is faster than yacc and |
+bison and which is both reentrant and threadsafe. |
+(Update: Since the previous sentence was written, bison |
+has also been updated so that it too can generate a |
+reentrant and threadsafe parser.) |
+Lemon also implements features that can be used |
to eliminate resource leaks, making is suitable for use |
in long-running programs such as graphical user interfaces |
or embedded controllers.</p> |
@@ -44,18 +47,18 @@ one and three files of outputs. |
automaton. |
</ul> |
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> |
+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. |
+<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 |
+grammar file is "gram.y". A typical use of Lemon would be the |
following command: |
<pre> |
lemon gram.y |
</pre> |
-This command will generate three output files named ``gram.c'', |
-``gram.h'' and ``gram.out''. |
+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 |
terminal symbols, and the last is the report that explains |
@@ -71,39 +74,35 @@ with a brief explanation of what each does by typing |
</pre> |
As of this writing, the following command-line options are supported: |
<ul> |
-<li><tt>-b</tt> |
-<li><tt>-c</tt> |
-<li><tt>-g</tt> |
-<li><tt>-m</tt> |
-<li><tt>-q</tt> |
-<li><tt>-s</tt> |
-<li><tt>-x</tt> |
+<li><b>-b</b> |
+Show only the basis for each parser state in the report file. |
+<li><b>-c</b> |
+Do not compress the generated action tables. |
+<li><b>-D<i>name</i></b> |
+Define C preprocessor macro <i>name</i>. This macro is useable by |
+"%ifdef" lines in the grammar file. |
+<li><b>-g</b> |
+Do not generate a parser. Instead write the input grammar to standard |
+output with all comments, actions, and other extraneous text removed. |
+<li><b>-l</b> |
+Omit "#line" directives in the generated parser C code. |
+<li><b>-m</b> |
+Cause the output C source code to be compatible with the "makeheaders" |
+program. |
+<li><b>-p</b> |
+Display all conflicts that are resolved by |
+<a href='#precrules'>precedence rules</a>. |
+<li><b>-q</b> |
+Suppress generation of the report file. |
+<li><b>-r</b> |
+Do not sort or renumber the parser states as part of optimization. |
+<li><b>-s</b> |
+Show parser statistics before existing. |
+<li><b>-T<i>file</i></b> |
+Use <i>file</i> as the template for the generated C-code parser implementation. |
+<li><b>-x</b> |
+Print the Lemon version number. |
</ul> |
-The ``-b'' option reduces the amount of text in the report file by |
-printing only the basis of each parser state, rather than the full |
-configuration. |
-The ``-c'' option suppresses action table compression. Using -c |
-will make the parser a little larger and slower but it will detect |
-syntax errors sooner. |
-The ``-g'' option causes no output files to be generated at all. |
-Instead, the input grammar file is printed on standard output but |
-with all comments, actions and other extraneous text deleted. This |
-is a useful way to get a quick summary of a grammar. |
-The ``-m'' option causes the output C source file to be compatible |
-with the ``makeheaders'' program. |
-Makeheaders is a program that automatically generates header files |
-from C source code. When the ``-m'' option is used, the header |
-file is not output since the makeheaders program will take care |
-of generated all header files automatically. |
-The ``-q'' option suppresses the report file. |
-Using ``-s'' causes a brief summary of parser statistics to be |
-printed. Like this: |
-<pre> |
- Parser statistics: 74 terminals, 70 nonterminals, 179 rules |
- 340 states, 2026 parser table entries, 0 conflicts |
-</pre> |
-Finally, the ``-x'' option causes Lemon to print its version number |
-and then stops without attempting to read the grammar or generate a parser.</p> |
<h3>The Parser Interface</h3> |
@@ -121,12 +120,12 @@ A new parser is created as follows: |
</pre> |
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 -- |
+The actual data structure used to represent a parser is opaque — |
its internal structure is not visible or usable by the calling routine. |
For this reason, the ParseAlloc() routine returns a pointer to void |
rather than a pointer to some particular structure. |
The sole argument to the ParseAlloc() routine is a pointer to the |
-subroutine used to allocate memory. Typically this means ``malloc()''.</p> |
+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 |
@@ -151,18 +150,19 @@ type of the next token in the data stream. |
There is one token type for each terminal symbol in the grammar. |
The gram.h file generated by Lemon contains #define statements that |
map symbolic terminal symbol names into appropriate integer values. |
-(A value of 0 for the second argument is a special flag to the |
-parser to indicate that the end of input has been reached.) |
+A value of 0 for the second argument is a special flag to the |
+parser to indicate that the end of input has been reached. |
The third argument is the value of the given token. By default, |
the type of the third argument is integer, but the grammar will |
usually redefine this type to be some kind of structure. |
Typically the second argument will be a broad category of tokens |
-such as ``identifier'' or ``number'' and the third argument will |
+such as "identifier" or "number" and the third argument will |
be the name of the identifier or the value of the number.</p> |
<p>The Parse() function may have either three or four arguments, |
-depending on the grammar. If the grammar specification file request |
-it, the Parse() function will have a fourth parameter that can be |
+depending on the grammar. If the grammar specification file requests |
+it (via the <a href='#extraarg'><tt>extra_argument</tt> directive</a>), |
+the Parse() function will have a fourth parameter that can be |
of any type chosen by the programmer. The parser doesn't do anything |
with this argument except to pass it through to action routines. |
This is a convenient mechanism for passing state information down |
@@ -192,7 +192,7 @@ following: |
</pre> |
This example shows a user-written routine that parses a file of |
text and returns a pointer to the parse tree. |
-(We've omitted all error-handling from this example to keep it |
+(All error-handling code is omitted from this example to keep it |
simple.) |
We assume the existence of some kind of tokenizer which is created |
using TokenizerCreate() on line 8 and deleted by TokenizerFree() |
@@ -263,6 +263,12 @@ 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> |
+<p><i>Updated as of 2016-02-16:</i> |
+The text above was written in the 1990s. |
+We are told that Bison has lately been enhanced to support the |
+tokenizer-calls-parser paradigm used by Lemon, and to obviate the |
+need for global variables.</p> |
+ |
<h2>Input File Syntax</h2> |
<p>The main purpose of the grammar specification file for Lemon is |
@@ -280,7 +286,7 @@ tokens) and it honors the same commenting conventions as C and C++.</p> |
<h3>Terminals and Nonterminals</h3> |
<p>A terminal symbol (token) is any string of alphanumeric |
-and underscore characters |
+and/or underscore characters |
that begins with an upper case letter. |
A terminal can contain lowercase letters after the first character, |
but the usual convention is to make terminals all upper case. |
@@ -307,7 +313,7 @@ must have alphanumeric names.</p> |
<p>The main component of a Lemon grammar file is a sequence of grammar |
rules. |
Each grammar rule consists of a nonterminal symbol followed by |
-the special symbol ``::='' and then a list of terminals and/or nonterminals. |
+the special symbol "::=" and then a list of terminals and/or nonterminals. |
The rule is terminated by a period. |
The list of terminals and nonterminals on the right-hand side of the |
rule can be empty. |
@@ -323,9 +329,9 @@ A typical sequence of grammar rules might look something like this: |
</pre> |
</p> |
-<p>There is one non-terminal in this example, ``expr'', and five |
-terminal symbols or tokens: ``PLUS'', ``TIMES'', ``LPAREN'', |
-``RPAREN'' and ``VALUE''.</p> |
+<p>There is one non-terminal in this example, "expr", and five |
+terminal symbols or tokens: "PLUS", "TIMES", "LPAREN", |
+"RPAREN" and "VALUE".</p> |
<p>Like yacc and bison, Lemon allows the grammar to specify a block |
of C code that will be executed whenever a grammar rule is reduced |
@@ -341,15 +347,15 @@ For example: |
<p>In order to be useful, grammar actions must normally be linked to |
their associated grammar rules. |
-In yacc and bison, this is accomplished by embedding a ``$$'' in the |
+In yacc and bison, this is accomplished by embedding a "$$" in the |
action to stand for the value of the left-hand side of the rule and |
-symbols ``$1'', ``$2'', and so forth to stand for the value of |
+symbols "$1", "$2", and so forth to stand for the value of |
the terminal or nonterminal at position 1, 2 and so forth on the |
right-hand side of the rule. |
This idea is very powerful, but it is also very error-prone. The |
single most common source of errors in a yacc or bison grammar is |
to miscount the number of symbols on the right-hand side of a grammar |
-rule and say ``$7'' when you really mean ``$8''.</p> |
+rule and say "$7" when you really mean "$8".</p> |
<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 |
@@ -379,7 +385,7 @@ For example, the rule |
<pre> |
expr(A) ::= expr(B) PLUS expr(C). { A = B; } |
</pre> |
-will generate an error because the linking symbol ``C'' is used |
+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 |
@@ -387,6 +393,7 @@ also facilitates the use of destructors for reclaiming memory |
allocated by the values of terminals and nonterminals on the |
right-hand side of a rule.</p> |
+<a name='precrules'></a> |
<h3>Precedence Rules</h3> |
<p>Lemon resolves parsing ambiguities in exactly the same way as |
@@ -398,7 +405,10 @@ whichever rule comes first in the grammar file.</p> |
yacc and bison, Lemon allows a measure of control |
over the resolution of paring conflicts using precedence rules. |
A precedence value can be assigned to any terminal symbol |
-using the %left, %right or %nonassoc directives. Terminal symbols |
+using the |
+<a href='#pleft'>%left</a>, |
+<a href='#pright'>%right</a> or |
+<a href='#pnonassoc'>%nonassoc</a> directives. Terminal symbols |
mentioned in earlier directives have a lower precedence that |
terminal symbols mentioned in later directives. For example:</p> |
@@ -518,7 +528,11 @@ other than that, the order of directives in Lemon is arbitrary.</p> |
<li><tt>%default_destructor</tt> |
<li><tt>%default_type</tt> |
<li><tt>%destructor</tt> |
+<li><tt>%endif</tt> |
<li><tt>%extra_argument</tt> |
+<li><tt>%fallback</tt> |
+<li><tt>%ifdef</tt> |
+<li><tt>%ifndef</tt> |
<li><tt>%include</tt> |
<li><tt>%left</tt> |
<li><tt>%name</tt> |
@@ -530,49 +544,57 @@ other than that, the order of directives in Lemon is arbitrary.</p> |
<li><tt>%stack_size</tt> |
<li><tt>%start_symbol</tt> |
<li><tt>%syntax_error</tt> |
+<li><tt>%token_class</tt> |
<li><tt>%token_destructor</tt> |
<li><tt>%token_prefix</tt> |
<li><tt>%token_type</tt> |
<li><tt>%type</tt> |
+<li><tt>%wildcard</tt> |
</ul> |
Each of these directives will be described separately in the |
following sections:</p> |
+<a name='pcode'></a> |
<h4>The <tt>%code</tt> directive</h4> |
-<p>The %code directive is used to specify addition C/C++ code that |
+<p>The %code directive is used to specify addition C code that |
is added to the end of the main output file. This is similar to |
-the %include directive except that %include is inserted at the |
-beginning of the main output file.</p> |
+the <a href='#pinclude'>%include</a> directive except that %include |
+is inserted at the beginning of the main output file.</p> |
<p>%code is typically used to include some action routines or perhaps |
-a tokenizer as part of the output file.</p> |
+a tokenizer or even the "main()" function |
+as part of the output file.</p> |
+<a name='default_destructor'></a> |
<h4>The <tt>%default_destructor</tt> directive</h4> |
<p>The %default_destructor directive specifies a destructor to |
use for non-terminals that do not have their own destructor |
specified by a separate %destructor directive. See the documentation |
-on the %destructor directive below for additional information.</p> |
+on the <a name='#destructor'>%destructor</a> directive below for |
+additional information.</p> |
<p>In some grammers, many different non-terminal symbols have the |
same datatype and hence the same destructor. This directive is |
a convenience way to specify the same destructor for all those |
non-terminals using a single statement.</p> |
+<a name='default_type'></a> |
<h4>The <tt>%default_type</tt> directive</h4> |
<p>The %default_type directive specifies the datatype of non-terminal |
symbols that do no have their own datatype defined using a separate |
-%type directive. See the documentation on %type below for addition |
-information.</p> |
+<a href='#ptype'>%type</a> directive. |
+</p> |
+<a name='destructor'></a> |
<h4>The <tt>%destructor</tt> directive</h4> |
<p>The %destructor directive is used to specify a destructor for |
a non-terminal symbol. |
-(See also the %token_destructor directive which is used to |
-specify a destructor for terminal symbols.)</p> |
+(See also the <a href='#token_destructor'>%token_destructor</a> |
+directive which is used to specify a destructor for terminal symbols.)</p> |
<p>A non-terminal's destructor is called to dispose of the |
non-terminal's value whenever the non-terminal is popped from |
@@ -595,28 +617,28 @@ or other resources held by that non-terminal.</p> |
</pre> |
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 |
+"nt" that holds values of type "void*". When the rule for |
+an "nt" reduces, it sets the value of the non-terminal to |
space obtained from malloc(). Later, when the nt non-terminal |
is popped from the stack, the destructor will fire and call |
free() on this malloced space, thus avoiding a memory leak. |
-(Note that the symbol ``$$'' in the destructor code is replaced |
+(Note that the symbol "$$" in the destructor code is replaced |
by the value of the non-terminal.)</p> |
<p>It is important to note that the value of a non-terminal is passed |
to the destructor whenever the non-terminal is removed from the |
stack, unless the non-terminal is used in a C-code action. If |
the non-terminal is used by C-code, then it is assumed that the |
-C-code will take care of destroying it if it should really |
-be destroyed. More commonly, the value is used to build some |
+C-code will take care of destroying it. |
+More commonly, the value is used to build some |
larger structure and we don't want to destroy it, which is why |
the destructor is not called in this circumstance.</p> |
-<p>By appropriate use of destructors, it is possible to |
-build a parser using Lemon that can be used within a long-running |
-program, such as a GUI, that will not leak memory or other resources. |
+<p>Destructors help avoid memory leaks by automatically freeing |
+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> |
<h4>The <tt>%extra_argument</tt> directive</h4> |
The %extra_argument directive instructs Lemon to add a 4th parameter |
@@ -630,17 +652,66 @@ and so forth. For example, if the grammar file contains:</p> |
</pre></p> |
<p>Then the Parse() function generated will have an 4th parameter |
-of type ``MyStruct*'' and all action routines will have access to |
-a variable named ``pAbc'' that is the value of the 4th parameter |
+of type "MyStruct*" and all action routines will have access to |
+a variable named "pAbc" that is the value of the 4th parameter |
in the most recent call to Parse().</p> |
+<a name='pfallback'></a> |
+<h4>The <tt>%fallback</tt> directive</h4> |
+ |
+<p>The %fallback directive specifies an alternative meaning for one |
+or more tokens. The alternative meaning is tried if the original token |
+would have generated a syntax error. |
+ |
+<p>The %fallback directive was added to support robust parsing of SQL |
+syntax in <a href="https://www.sqlite.org/">SQLite</a>. |
+The SQL language contains a large assortment of keywords, each of which |
+appears as a different token to the language parser. SQL contains so |
+many keywords, that it can be difficult for programmers to keep up with |
+them all. Programmers will, therefore, sometimes mistakenly use an |
+obscure language keyword for an identifier. The %fallback directive |
+provides a mechanism to tell the parser: "If you are unable to parse |
+this keyword, try treating it as an identifier instead." |
+ |
+<p>The syntax of %fallback is as follows: |
+ |
+<blockquote> |
+<tt>%fallback</tt> <i>ID</i> <i>TOKEN...</i> <b>.</b> |
+</blockquote> |
+ |
+<p>In words, the %fallback directive is followed by a list of token names |
+terminated by a period. The first token name is the fallback token - the |
+token to which all the other tokens fall back to. The second and subsequent |
+arguments are tokens which fall back to the token identified by the first |
+argument. |
+ |
+<a name='pifdef'></a> |
+<h4>The <tt>%ifdef</tt>, <tt>%ifndef</tt>, and <tt>%endif</tt> directives.</h4> |
+ |
+<p>The %ifdef, %ifndef, and %endif directives are similar to |
+#ifdef, #ifndef, and #endif in the C-preprocessor, just not as general. |
+Each of these directives must begin at the left margin. No whitespace |
+is allowed between the "%" and the directive name. |
+ |
+<p>Grammar text in between "%ifdef MACRO" and the next nested "%endif" is |
+ignored unless the "-DMACRO" command-line option is used. Grammar text |
+betwen "%ifndef MACRO" and the next nested "%endif" is included except when |
+the "-DMACRO" command-line option is used. |
+ |
+<p>Note that the argument to %ifdef and %ifndef must be a single |
+preprocessor symbol name, not a general expression. There is no "%else" |
+directive. |
+ |
+ |
+<a name='pinclude'></a> |
<h4>The <tt>%include</tt> directive</h4> |
<p>The %include directive specifies C code that is included at the |
top of the generated parser. You can include any text you want -- |
the Lemon parser generator copies it blindly. If you have multiple |
-%include directives in your grammar file the value of the last |
-%include directive overwrites all the others.</p. |
+%include directives in your grammar file, their values are concatenated |
+so that all %include code ultimately appears near the top of the |
+generated parser, in the same order as it appeared in the grammer.</p> |
<p>The %include directive is very handy for getting some extra #include |
preprocessor statements at the beginning of the generated parser. |
@@ -653,12 +724,13 @@ For example:</p> |
<p>This might be needed, for example, if some of the C actions in the |
grammar call functions that are prototyed in unistd.h.</p> |
+<a name='pleft'></a> |
<h4>The <tt>%left</tt> directive</h4> |
-The %left directive is used (along with the %right and |
-%nonassoc directives) to declare precedences of terminal |
-symbols. Every terminal symbol whose name appears after |
-a %left directive but before the next period (``.'') is |
+The %left directive is used (along with the <a href='#pright'>%right</a> and |
+<a href='#pnonassoc'>%nonassoc</a> directives) to declare precedences of |
+terminal symbols. Every terminal symbol whose name appears after |
+a %left directive but before the next period (".") is |
given the same left-associative precedence value. Subsequent |
%left directives have higher precedence. For example:</p> |
@@ -679,10 +751,11 @@ a large amount of stack space if you make heavy use or right-associative |
operators. For this reason, it is recommended that you use %left |
rather than %right whenever possible.</p> |
+<a name='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 |
+five-character string "Parse". You can change this string to something |
different using the %name directive. For instance:</p> |
<p><pre> |
@@ -701,16 +774,19 @@ The %name directive allows you to generator two or more different |
parsers and link them all into the same executable. |
</p> |
+<a name='pnonassoc'></a> |
<h4>The <tt>%nonassoc</tt> directive</h4> |
<p>This directive is used to assign non-associative precedence to |
-one or more terminal symbols. See the section on precedence rules |
-or on the %left directive for additional information.</p> |
+one or more terminal symbols. See the section on |
+<a href='#precrules'>precedence rules</a> |
+or on the <a href='#pleft'>%left</a> directive for additional information.</p> |
+<a name='parse_accept'></a> |
<h4>The <tt>%parse_accept</tt> directive</h4> |
<p>The %parse_accept directive specifies a block of C code that is |
-executed whenever the parser accepts its input string. To ``accept'' |
+executed whenever the parser accepts its input string. To "accept" |
an input string means that the parser was able to process all tokens |
without error.</p> |
@@ -722,7 +798,7 @@ without error.</p> |
} |
</pre></p> |
- |
+<a name='parse_failure'></a> |
<h4>The <tt>%parse_failure</tt> directive</h4> |
<p>The %parse_failure directive specifies a block of C code that |
@@ -737,12 +813,15 @@ only invoked when parsing is unable to continue.</p> |
} |
</pre></p> |
+<a name='pright'></a> |
<h4>The <tt>%right</tt> directive</h4> |
<p>This directive is used to assign right-associative precedence to |
-one or more terminal symbols. See the section on precedence rules |
-or on the %left directive for additional information.</p> |
+one or more terminal symbols. See the section on |
+<a href='#precrules'>precedence rules</a> |
+or on the <a href='#pleft'>%left</a> directive for additional information.</p> |
+<a name='stack_overflow'></a> |
<h4>The <tt>%stack_overflow</tt> directive</h4> |
<p>The %stack_overflow directive specifies a block of C code that |
@@ -771,6 +850,7 @@ Not like this: |
list ::= . |
</pre> |
+<a name='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 |
@@ -783,6 +863,7 @@ with a stack of the requested size. The default value is 100.</p> |
%stack_size 2000 |
</pre></p> |
+<a name='start_symbol'></a> |
<h4>The <tt>%start_symbol</tt> directive</h4> |
<p>By default, the start-symbol for the grammar that Lemon generates |
@@ -793,6 +874,7 @@ can choose a different start-symbol using the %start_symbol directive.</p> |
%start_symbol prog |
</pre></p> |
+<a name='token_destructor'></a> |
<h4>The <tt>%token_destructor</tt> directive</h4> |
<p>The %destructor directive assigns a destructor to a non-terminal |
@@ -805,6 +887,7 @@ the %token_type 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> |
<h4>The <tt>%token_prefix</tt> directive</h4> |
<p>Lemon generates #defines that assign small integer constants |
@@ -830,6 +913,7 @@ to cause Lemon to produce these symbols instead: |
#define TOKEN_PLUS 4 |
</pre> |
+<a name='token_type'></a><a name='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 |
@@ -845,7 +929,7 @@ token structure. Like this:</p> |
</pre></p> |
<p>If the data type of terminals is not specified, the default value |
-is ``int''.</p> |
+is "void*".</p> |
<p>Non-terminal symbols can each have their own data types. Typically |
the data type of a non-terminal is a pointer to the root of a parse-tree |
@@ -866,6 +950,17 @@ non-terminal whose data type requires 1K of storage, then your 100 |
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> |
+<h4>The <tt>%wildcard</tt> directive</h4> |
+ |
+<p>The %wildcard directive is followed by a single token name and a |
+period. This directive specifies that the identified token should |
+match any input token. |
+ |
+<p>When the generated parser has the choice of matching an input against |
+the wildcard token and some other token, the other token is always used. |
+The wildcard token is only matched if there are no other alternatives. |
+ |
<h3>Error Processing</h3> |
<p>After extensive experimentation over several years, it has been |
@@ -877,7 +972,7 @@ first invokes the code specified by the %syntax_error directive, if |
any. It then enters its error recovery strategy. The error recovery |
strategy is to begin popping the parsers stack until it enters a |
state where it is permitted to shift a special non-terminal symbol |
-named ``error''. It then shifts this non-terminal and continues |
+named "error". It then shifts this non-terminal and continues |
parsing. But the %syntax_error routine will not be called again |
until at least three new tokens have been successfully shifted.</p> |
@@ -886,7 +981,7 @@ is unable to shift the error symbol, then the %parse_failed routine |
is invoked and the parser resets itself to its start state, ready |
to begin parsing a new file. This is what will happen at the very |
first syntax error, of course, if there are no instances of the |
-``error'' non-terminal in your grammar.</p> |
+"error" non-terminal in your grammar.</p> |
</body> |
</html> |