From: Joel E. Denny <jdenny@ces.clemson.edu> Date: Sat, 18 Aug 2007 00:07:01 +0000 (+0000) Subject: * doc/bison.texinfo (Push Decl): Document the push parser. X-Git-Tag: v2.3b~104 X-Git-Url: https://git.saurik.com/bison.git/commitdiff_plain/9987d1b3cce14fd74c4bc382048254697c2de945?ds=inline * doc/bison.texinfo (Push Decl): Document the push parser. (Table of Symbols): Ditto. (Pure Decl): Ditto. (Decl Summary): Ditto. (Multiple Parsers, Push Parser Function, Pull Parser Function, Parser Create Function, Parser Delete Function): Add new push parser symbols. (Table of Symbols): Document push-parser, push-pull-parser, yypush_parse, yypull_parse, yypstate_new and yypstate_delete. --- diff --git a/ChangeLog b/ChangeLog index 662d7bcb..4409f14e 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,15 @@ +2007-08-17 Bob Rossi <bob@brasko.net> + + * doc/bison.texinfo (Push Decl): Document the push parser. + (Table of Symbols): Ditto. + (Pure Decl): Ditto. + (Decl Summary): Ditto. + (Multiple Parsers, Push Parser Function, Pull Parser Function, + Parser Create Function, Parser Delete Function): + Add new push parser symbols. + (Table of Symbols): Document push-parser, push-pull-parser, + yypush_parse, yypull_parse, yypstate_new and yypstate_delete. + 2007-08-15 Paul Eggert <eggert@cs.ucla.edu> Update to GPLv3. diff --git a/doc/bison.texinfo b/doc/bison.texinfo index 56540f08..ab3a6a8a 100644 --- a/doc/bison.texinfo +++ b/doc/bison.texinfo @@ -224,6 +224,7 @@ Bison Declarations * Expect Decl:: Suppressing warnings about parsing conflicts. * Start Decl:: Specifying the start symbol. * Pure Decl:: Requesting a reentrant parser. +* Push Decl:: Requesting a push parser. * Decl Summary:: Table of all Bison declarations. Parser C-Language Interface @@ -3980,6 +3981,7 @@ Grammars}). * Expect Decl:: Suppressing warnings about parsing conflicts. * Start Decl:: Specifying the start symbol. * Pure Decl:: Requesting a reentrant parser. +* Push Decl:: Requesting a push parser. * Decl Summary:: Table of all Bison declarations. @end menu @@ -4512,8 +4514,9 @@ The result is that the communication variables @code{yylval} and @code{yylloc} become local variables in @code{yyparse}, and a different calling convention is used for the lexical analyzer function @code{yylex}. @xref{Pure Calling, ,Calling Conventions for Pure -Parsers}, for the details of this. The variable @code{yynerrs} also -becomes local in @code{yyparse} (@pxref{Error Reporting, ,The Error +Parsers}, for the details of this. The variable @code{yynerrs} +becomes local in @code{yyparse} in pull mode but it becomes a member +of yypstate in push mode. (@pxref{Error Reporting, ,The Error Reporting Function @code{yyerror}}). The convention for calling @code{yyparse} itself is unchanged. @@ -4521,6 +4524,112 @@ Whether the parser is pure has nothing to do with the grammar rules. You can generate either a pure parser or a nonreentrant parser from any valid grammar. +@node Push Decl +@subsection A Push Parser +@cindex push parser +@cindex push parser +@findex %push-parser + +A pull parser is called once and it takes control until all its input +is completely parsed. A push parser, on the other hand, is called +each time a new token is made available. + +A push parser is typically useful when the parser is part of a +main event loop in the client's application. This is typically +a requirement of a GUI, when the main event loop needs to be triggered +within a certain time period. + +Normally, Bison generates a pull parser. The Bison declaration +@code{%push-parser} says that you want the parser to be a push parser. +It looks like this: + +@example +%push-parser +@end example + +In almost all cases, you want to ensure that your push parser is also +a pure parser (@pxref{Pure Decl, ,A Pure (Reentrant) Parser}). The only +time you should create an impure push parser is to have backwards +compatibility with the impure Yacc pull mode interface. Unless you know +what you are doing, your declarations should look like this: + +@example +%pure-parser +%push-parser +@end example + +There is a major notable functional difference between the pure push parser +and the impure push parser. It is acceptable for a pure push parser to have +many parser instances, of the same type of parser, in memory at the same time. +An impure push parser should only use one parser at a time. + +When a push parser is selected, Bison will generate some new symbols in +the generated parser. @code{yypstate} is a structure that the generated +parser uses to store the parser's state. @code{yypstate_new} is the +function that will create a new parser instance. @code{yypstate_delete} +will free the resources associated with the corresponding parser instance. +Finally, @code{yypush_parse} is the function that should be called whenever a +token is available to provide the parser. A trivial example +of using a pure push parser would look like this: + +@example +int status; +yypstate *ps = yypstate_new (); +do @{ + status = yypush_parse (ps, yylex (), NULL); +@} while (status == YYPUSH_MORE); +yypstate_delete (ps); +@end example + +If the user decided to use an impure push parser, a few things about +the generated parser will change. The @code{yychar} variable becomes +a global variable instead of a variable in the @code{yypush_parse} function. +For this reason, the signature of the @code{yypush_parse} function is +changed to remove the token as a parameter. A nonreentrant push parser +example would thus look like this: + +@example +extern int yychar; +int status; +yypstate *ps = yypstate_new (); +do @{ + yychar = yylex (); + status = yypush_parse (ps); +@} while (status == YYPUSH_MORE); +yypstate_delete (ps); +@end example + +That's it. Notice the next token is put into the global variable @code{yychar} +for use by the next invocation of the @code{yypush_parse} function. + +Bison also supports both the push parser interface along with the pull parser +interface in the same generated parser. In order to get this functionality, +you should replace the @code{%push-parser} declaration with the +@code{%push-pull-parser} declaration. Doing this will create all of the +symbols mentioned earlier along with the two extra symbols, @code{yyparse} +and @code{yypull_parse}. @code{yyparse} can be used exactly as it normally +would be used. However, the user should note that it is implemented in the +generated parser by calling @code{yypull_parse}. This makes the +@code{yyparse} function that is generated with the @code{%push-pull-parser} +declaration slower than the normal @code{yyparse} function. If the user +calls the @code{yypull_parse} function it will parse the rest of the input +stream. It is possible to @code{yypush_parse} tokens to select a subgrammar +and then @code{yypull_parse} the rest of the input stream. If you would like +to switch back and forth between between parsing styles, you would have to +write your own @code{yypull_parse} function that knows when to quit looking +for input. An example of using the @code{yypull_parse} function would look +like this: + +@example +yypstate *ps = yypstate_new (); +yypull_parse (ps); /* Will call the lexer */ +yypstate_delete (ps); +@end example + +Adding the @code{%pure-parser} declaration does exactly the same thing to the +generated parser with @code{%push-pull-parser} as it did for +@code{%push-parser}. + @node Decl Summary @subsection Bison Declaration Summary @cindex Bison declaration summary @@ -4799,10 +4908,13 @@ Rename the external symbols used in the parser so that they start with in C parsers is @code{yyparse}, @code{yylex}, @code{yyerror}, @code{yynerrs}, @code{yylval}, @code{yychar}, @code{yydebug}, and -(if locations are used) @code{yylloc}. For example, if you use -@samp{%name-prefix "c_"}, the names become @code{c_parse}, @code{c_lex}, -and so on. In C++ parsers, it is only the surrounding namespace which is -named @var{prefix} instead of @samp{yy}. +(if locations are used) @code{yylloc}. If you use a push parser, +@code{yypush_parse}, @code{yypull_parse}, @code{yypstate}, +@code{yypstate_new} and @code{yypstate_delete} will +also be renamed. For example, if you use @samp{%name-prefix "c_"}, the +names become @code{c_parse}, @code{c_lex}, and so on. In C++ parsers, +it is only the surrounding namespace which is named @var{prefix} instead +of @samp{yy}. @xref{Multiple Parsers, ,Multiple Parsers in the Same Program}. @end deffn @@ -4832,6 +4944,16 @@ Request a pure (reentrant) parser program (@pxref{Pure Decl, ,A Pure (Reentrant) Parser}). @end deffn +@deffn {Directive} %push-parser +Bison declaration to request a push parser. +@xref{Push Decl, ,A Push Parser}. +@end deffn + +@deffn {Directive} %push-pull-parser +Bison declaration to request a push and a pull parser. +@xref{Push Decl, ,A Push Parser}. +@end deffn + @deffn {Directive} %require "@var{version}" Require version @var{version} or higher of Bison. @xref{Require Decl, , Require a Version of Bison}. @@ -4915,8 +5037,11 @@ names that do not conflict. The precise list of symbols renamed is @code{yyparse}, @code{yylex}, @code{yyerror}, @code{yynerrs}, @code{yylval}, @code{yylloc}, -@code{yychar} and @code{yydebug}. For example, if you use @samp{-p c}, -the names become @code{cparse}, @code{clex}, and so on. +@code{yychar} and @code{yydebug}. If you use a push parser, +@code{yypush_parse}, @code{yypull_parse}, @code{yypstate}, +@code{yypstate_new} and @code{yypstate_delete} will also be renamed. +For example, if you use @samp{-p c}, the names become @code{cparse}, +@code{clex}, and so on. @strong{All the other variables and macros associated with Bison are not renamed.} These others are not global; there is no conflict if the same @@ -4945,6 +5070,12 @@ in the grammar file, you are likely to run into trouble. @menu * Parser Function:: How to call @code{yyparse} and what it returns. +* Push Parser Function:: How to call @code{yypush_parse} and what it returns. +* Pull Parser Function:: How to call @code{yypull_parse} and what it returns. +* Parser Create Function:: How to call @code{yypstate_new} and what it + returns. +* Parser Delete Function:: How to call @code{yypstate_delete} and what it + returns. * Lexical:: You must supply a function @code{yylex} which reads tokens. * Error Reporting:: You must supply a function @code{yyerror}. @@ -5027,6 +5158,61 @@ In the grammar actions, use expressions like this to refer to the data: exp: @dots{} @{ @dots{}; *randomness += 1; @dots{} @} @end example +@node Push Parser Function +@section The Push Parser Function @code{yypush_parse} +@findex yypush_parse + +You call the function @code{yypush_parse} to parse a single token. This +function is available if either the @code{%push-parser} or +@code{%push-pull-parser} declaration is used. +@xref{Push Decl, ,A Push Parser}. + +@deftypefun int yypush_parse (yypstate *yyps) +The value returned by @code{yypush_parse} is the same as for yyparse with the +following exception. @code{yypush_parse} will return YYPUSH_MORE if more input +is required to finish parsing the grammar. +@end deftypefun + +@node Pull Parser Function +@section The Pull Parser Function @code{yypull_parse} +@findex yypull_parse + +You call the function @code{yypull_parse} to parse the rest of the input +stream. This function is available if the @code{%push-pull-parser} +declaration is used. +@xref{Push Decl, ,A Push Parser}. + +@deftypefun int yypull_parse (yypstate *yyps) +The value returned by @code{yypull_parse} is the same as for @code{yyparse}. +@end deftypefun + +@node Parser Create Function +@section The Parser Create Function @code{yystate_new} +@findex yypstate_new + +You call the function @code{yypstate_new} to create a new parser instance. +This function is available if either the @code{%push-parser} or +@code{%push-pull-parser} declaration is used. +@xref{Push Decl, ,A Push Parser}. + +@deftypefun yypstate *yypstate_new (void) +The fuction will return a valid parser instance if there was memory available +or NULL if no memory was available. +@end deftypefun + +@node Parser Delete Function +@section The Parser Delete Function @code{yystate_delete} +@findex yypstate_delete + +You call the function @code{yypstate_delete} to delete a parser instance. +This function is available if either the @code{%push-parser} or +@code{%push-pull-parser} declaration is used. +@xref{Push Decl, ,A Push Parser}. + +@deftypefun void yypstate_delete (yypstate *yyps) +This function will reclaim the memory associated with a parser instance. +After this call, you should no longer attempt to use the parser instance. +@end deftypefun @node Lexical @section The Lexical Analyzer Function @code{yylex} @@ -9266,6 +9452,16 @@ Bison declaration to request a pure (reentrant) parser. @xref{Pure Decl, ,A Pure (Reentrant) Parser}. @end deffn +@deffn {Directive} %push-parser +Bison declaration to request a push parser. +@xref{Push Decl, ,A Push Parser}. +@end deffn + +@deffn {Directive} %push-pull-parser +Bison declaration to request a push and a pull parser. +@xref{Push Decl, ,A Push Parser}. +@end deffn + @deffn {Directive} %require "@var{version}" Require version @var{version} or higher of Bison. @xref{Require Decl, , Require a Version of Bison}. @@ -9440,7 +9636,8 @@ Management}. @deffn {Variable} yynerrs Global variable which Bison increments each time it reports a syntax error. -(In a pure parser, it is a local variable within @code{yyparse}.) +(In a pure parser, it is a local variable within @code{yyparse}. In a +pure push parser, it is a member of yypstate.) @xref{Error Reporting, ,The Error Reporting Function @code{yyerror}}. @end deffn @@ -9449,6 +9646,33 @@ The parser function produced by Bison; call this function to start parsing. @xref{Parser Function, ,The Parser Function @code{yyparse}}. @end deffn +@deffn {Function} yypstate_delete +The function to delete a parser instance, produced by Bison in push mode; +call this function to delete the memory associated with a parser. +@xref{Parser Delete Function, ,The Parser Delete Function +@code{yypstate_delete}}. +@end deffn + +@deffn {Function} yypstate_new +The function to create a parser instance, produced by Bison in push mode; +call this function to create a new parser. +@xref{Parser Create Function, ,The Parser Create Function +@code{yypstate_new}}. +@end deffn + +@deffn {Function} yypull_parse +The parser function produced by Bison in push mode; call this function to +parse the rest of the input stream. +@xref{Pull Parser Function, ,The Pull Parser Function +@code{yypull_parse}}. +@end deffn + +@deffn {Function} yypush_parse +The parser function produced by Bison in push mode; call this function to +parse a single token. @xref{Push Parser Function, ,The Push Parser Function +@code{yypush_parse}}. +@end deffn + @deffn {Macro} YYPARSE_PARAM An obsolete macro for specifying the name of a parameter that @code{yyparse} should accept. The use of this macro is deprecated, and