| 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>
|
|
|