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flex编译器的源代码

	  scan started was a newline.  The mechanism now is that '^' is
	  active iff the last token ended in a newline (or the last call to
	  input() returned a newline).  For most users, the difference in
	  mechanisms is negligible.  Where it will make a difference,
	  however, is if unput() or yyless() is used to alter the input
	  stream.  When in doubt, use yy_set_bol().

	- The new beginning-of-line mechanism involved changing some fairly
	  twisted code, so it may have introduced bugs - beware ...

	- The macro YY_AT_BOL() returns true if the next token scanned from
	  the current buffer will have '^' rules active, false otherwise.

	- The new function

		void yy_flush_buffer( struct yy_buffer_state* b )

	  flushes the contents of the current buffer (i.e., next time
	  the scanner attempts to match a token using b as the current
	  buffer, it will begin by invoking YY_INPUT to fill the buffer).
	  This routine is also available to C++ scanners (unlike some
	  of the other new routines).

	  The related macro

		YY_FLUSH_BUFFER

	  flushes the contents of the current buffer.

	- A new "-ooutput" option writes the generated scanner to "output".
	  If used with -t, the scanner is still written to stdout, but
	  its internal #line directives (see previous item) use "output".

	- Flex now generates #line directives relating the code it
	  produces to the output file; this means that error messages
	  in the flex-generated code should be correctly pinpointed.

	- When generating #line directives, filenames with embedded '\'s
	  have those characters escaped (i.e., turned into '\\').  This
	  feature helps with reporting filenames for some MS-DOS and OS/2
	  systems.

	- The FlexLexer class includes two new public member functions:

		virtual void switch_streams( istream* new_in = 0,
						ostream* new_out = 0 )

	  reassigns yyin to new_in (if non-nil) and yyout to new_out
	  (ditto), deleting the previous input buffer if yyin is
	  reassigned.  It is used by:

		int yylex( istream* new_in = 0, ostream* new_out = 0 )

	  which first calls switch_streams() and then returns the value
	  of calling yylex().

	- C++ scanners now have yy_flex_debug as a member variable of
	  FlexLexer rather than a global, and member functions for testing
	  and setting it.

	- When generating a C++ scanning class, you can now use

		%option yyclass="foo"

	  to inform flex that you have derived "foo" as a subclass of
	  yyFlexLexer, so flex will place your actions in the member
	  function foo::yylex() instead of yyFlexLexer::yylex().  It also
	  generates a yyFlexLexer::yylex() member function that generates a
	  run-time error if called (by invoking yyFlexLexer::LexerError()).
	  This feature is necessary if your subclass "foo" introduces some
	  additional member functions or variables that you need to access
	  from yylex().

	- Current texinfo files in MISC/texinfo, contributed by Francois
	  Pinard.

	- You can now change the name "flex" to something else (e.g., "lex")
	  by redefining $(FLEX) in the Makefile.

	- Two bugs (one serious) that could cause "bigcheck" to fail have
	  been fixed.

	- A number of portability/configuration changes have been made
	  for easier portability.

	- You can use "YYSTATE" in your scanner as an alias for YY_START
	  (for AT&T lex compatibility).

	- input() now maintains yylineno.

	- input() no longer trashes yytext.

	- interactive scanners now read characters in YY_INPUT up to a
	  newline, a large performance gain.

	- C++ scanner objects now work with the -P option.  You include
	  <FlexLexer.h> once per scanner - see comments in <FlexLexer.h>
	  (or flex.1) for details.

	- C++ FlexLexer objects now use the "cerr" stream to report -d output
	  instead of stdio.

	- The -c flag now has its full glorious POSIX interpretation (do
	  nothing), rather than being interpreted as an old-style -C flag.

	- Scanners generated by flex now include two #define's giving
	  the major and minor version numbers (YY_FLEX_MAJOR_VERSION,
	  YY_FLEX_MINOR_VERSION).  These can then be tested to see
	  whether certain flex features are available.

	- Scanners generated using -l lex compatibility now have the symbol
	  YY_FLEX_LEX_COMPAT #define'd.

	- When initializing (i.e., yy_init is non-zero on entry to yylex()),
	  generated scanners now set yy_init to zero before executing
	  YY_USER_INIT.  This means that you can set yy_init back to a
	  non-zero value in YY_USER_INIT if you need the scanner to be
	  reinitialized on the next call.

	- You can now use "#line" directives in the first section of your
	  scanner specification.

	- When generating full-table scanners (-Cf), flex now puts braces
	  around each row of the 2-d array initialization, to silence warnings
	  on over-zealous compilers.

	- Improved support for MS-DOS.  The flex sources have been successfully
	  built, unmodified, for Borland 4.02 (all that's required is a
	  Borland Makefile and config.h file, which are supplied in
	  MISC/Borland - contributed by Terrence O Kane).

	- Improved support for Macintosh using Think C - the sources should
	  build for this platform "out of the box".  Contributed by Scott
	  Hofmann.

	- Improved support for VMS, in MISC/VMS/, contributed by Pat Rankin.

	- Support for the Amiga, in MISC/Amiga/, contributed by Andreas
	  Scherer.  Note that the contributed files were developed for
	  flex 2.4 and have not been tested with flex 2.5.

	- Some notes on support for the NeXT, in MISC/NeXT, contributed
	  by Raf Schietekat.

	- The MISC/ directory now includes a preformatted version of flex.1
	  in flex.man, and pre-yacc'd versions of parse.y in parse.{c,h}.

	- The flex.1 and flexdoc.1 manual pages have been merged.  There
	  is now just one document, flex.1, which includes an overview
	  at the beginning to help you find the section you need.

	- Documentation now clarifies that start conditions persist across
	  switches to new input files or different input buffers.  If you
	  want to e.g., return to INITIAL, you must explicitly do so.

	- The "Performance Considerations" section of the manual has been
	  updated.

	- Documented the "yy_act" variable, which when YY_USER_ACTION is
	  invoked holds the number of the matched rule, and added an
	  example of using yy_act to profile how often each rule is matched.

	- Added YY_NUM_RULES, a definition that gives the total number
	  of rules in the file, including the default rule (even if you
	  use -s).

	- Documentation now clarifies that you can pass a nil FILE* pointer
	  to yy_create_buffer() or yyrestart() if you've arrange YY_INPUT
	  to not need yyin.

	- Documentation now clarifies that YY_BUFFER_STATE is a pointer to
	  an opaque "struct yy_buffer_state".

	- Documentation now stresses that you gain the benefits of removing
	  backing-up states only if you remove *all* of them.

	- Documentation now points out that traditional lex allows you
	  to put the action on a separate line from the rule pattern if
	  the pattern has trailing whitespace (ugh!), but flex doesn't
	  support this.

	- A broken example in documentation of the difference between
	  inclusive and exclusive start conditions is now fixed.

	- Usage (-h) report now goes to stdout.

	- Version (-V) info now goes to stdout.

	- More #ifdef chud has been added to the parser in attempt to
	  deal with bison's use of alloca().

	- "make clean" no longer deletes emacs backup files (*~).

	- Some memory leaks have been fixed.

	- A bug was fixed in which dynamically-expanded buffers were
	  reallocated a couple of bytes too small.

	- A bug was fixed which could cause flex to read and write beyond
	  the end of the input buffer.

	- -S will not be going away.


Changes between release 2.4.7 (03Aug94) and release 2.4.6:

	- Fixed serious bug in reading multiple files.

	- Fixed bug in scanning NUL's.

	- Fixed bug in input() returning 8-bit characters.

	- Fixed bug in matching text with embedded NUL's when
	  using %array or lex compatibility.

	- Fixed multiple invocations of YY_USER_ACTION when using '|'
	  continuation action.

	- Minor prototyping fixes.

Changes between release 2.4.6 (04Jan94) and release 2.4.5:

	- Linking with -lfl no longer required if your program includes
	  its own yywrap() and main() functions.  (This change will cause
	  problems if you have a non-ANSI compiler on a system for which
	  sizeof(int) != sizeof(void*) or sizeof(int) != sizeof(size_t).)

	- The use of 'extern "C++"' in FlexLexer.h has been modified to
	  get around an incompatibility with g++'s header files.

Changes between release 2.4.5 (11Dec93) and release 2.4.4:

	- Fixed bug breaking C++ scanners that use REJECT or variable
	  trailing context.

	- Fixed serious input problem for interactive scanners on
	  systems for which char is unsigned.

	- Fixed bug in incorrectly treating '$' operator as variable
	  trailing context.

	- Fixed bug in -CF table representation that could lead to
	  corrupt tables.

	- Fixed fairly benign memory leak.

	- Added `extern "C++"' wrapper to FlexLexer.h header.  This
	  should overcome the g++ 2.5.X problems mentioned in the
	  NEWS for release 2.4.3.

	- Changed #include of FlexLexer.h to use <> instead of "".

	- Added feature to control whether the scanner attempts to
	  refill the input buffer once it's exhausted.  This feature
	  will be documented in the 2.5 release.


Changes between release 2.4.4 (07Dec93) and release 2.4.3:

	- Fixed two serious bugs in scanning 8-bit characters.

	- Fixed bug in YY_USER_ACTION that caused it to be executed
	  inappropriately (on the scanner's own internal actions, and
	  with incorrect yytext/yyleng values).

	- Fixed bug in pointing yyin at a new file and resuming scanning.

	- Portability fix regarding min/max/abs macros conflicting with
	  function definitions in standard header files.

	- Added a virtual LexerError() method to the C++ yyFlexLexer class
	  for reporting error messages instead of always using cerr.

	- Added warning in flexdoc that the C++ scanning class is presently
	  experimental and subject to considerable change between major
	  releases.


Changes between release 2.4.3 (03Dec93) and release 2.4.2:

	- Fixed bug causing fatal scanner messages to fail to print.

	- Fixed things so FlexLexer.h can be included in other C++
	  sources.  One side-effect of this change is that -+ and -CF
	  are now incompatible.

	- libfl.a now supplies private versions of the the <string.h>/
	  <strings.h> string routines needed by flex and the scanners
	  it generates, to enhance portability to some BSD systems.

	- More robust solution to 2.4.2's flexfatal() bug fix.

	- Added ranlib of installed libfl.a.

	- Some lint tweaks.

	- NOTE: problems have been encountered attempting to build flex
	  C++ scanners using g++ version 2.5.X.  The problem is due to an
	  unfortunate heuristic in g++ 2.5.X that attempts to discern between
	  C and C++ headers.  Because FlexLexer.h is installed (by default)
	  in /usr/local/include and not /usr/local/lib/g++-include, g++ 2.5.X
	  decides that it's a C header :-(.  So if you have problems, install