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Annotation of researchv10dc/cmd/flex/Changes, revision 1.1.1.1

1.1       root        1: Changes between 2.1 beta-test release of June '89 and previous release:
                      2: 
                      3:     User-visible:
                      4: 
                      5:        - -p flag generates a performance report to stderr.  The report
                      6:          consists of comments regarding features of the scanner rules
                      7:          which result in slower scanners.
                      8: 
                      9:        - -b flag generates backtracking information to lex.backtrack.
                     10:          This is a list of scanner states which require backtracking
                     11:          and the characters on which they do so.  By adding rules
                     12:          one can remove backtracking states.  If all backtracking states
                     13:          are eliminated, the generated scanner will run faster.
                     14:          Backtracking is not yet documented in the manual entry.
                     15: 
                     16:        - Variable trailing context now works, i.e., one can have
                     17:          rules like "(foo)*/[ \t]*bletch".  Some trailing context
                     18:          patterns still cannot be properly matched and generate
                     19:          error messages.  These are patterns where the ending of the
                     20:          first part of the rule matches the beginning of the second
                     21:          part, such as "zx*/xy*", where the 'x*' matches the 'x' at
                     22:          the beginning of the trailing context.  Lex won't get these
                     23:          patterns right either.
                     24: 
                     25:        - Faster scanners.
                     26: 
                     27:        - End-of-file rules.  The special rule "<<EOF>>" indicates
                     28:          actions which are to be taken when an end-of-file is
                     29:          encountered and yywrap() returns non-zero (i.e., indicates
                     30:          no further files to process).  See manual entry for example.
                     31: 
                     32:        - The -r (reject used) flag is gone.  flex now scans the input
                     33:          for occurrences of the string "REJECT" to determine if the
                     34:          action is needed.  It tries to be intelligent about this but
                     35:          can be fooled.  One can force the presence or absence of
                     36:          REJECT by adding a line in the first section of the form
                     37:          "%used REJECT" or "%unused REJECT".
                     38: 
                     39:        - yymore() has been implemented.  Similarly to REJECT, flex
                     40:          detects the use of yymore(), which can be overridden using
                     41:          "%used" or "%unused".
                     42: 
                     43:        - Patterns like "x{0,3}" now work (i.e., with lower-limit == 0).
                     44: 
                     45:        - Removed '\^x' for ctrl-x misfeature.
                     46: 
                     47:        - Added '\a' and '\v' escape sequences.
                     48: 
                     49:        - \<digits> now works for octal escape sequences; previously
                     50:          \0<digits> was required.
                     51: 
                     52:        - Better error reporting; line numbers are associated with rules.
                     53: 
                     54:        - yyleng is a macro; it cannot be accessed outside of the
                     55:          scanner source file.
                     56: 
                     57:        - yytext and yyleng should not be modified within a flex action.
                     58: 
                     59:        - Generated scanners #define the name FLEX_SCANNER.
                     60: 
                     61:        - Rules are internally separated by YY_BREAK in lex.yy.c rather
                     62:          than break, to allow redefinition.
                     63: 
                     64:        - The macro YY_USER_ACTION can be redefined to provide an action
                     65:          which is always executed prior to the matched rule's action.
                     66:        
                     67:        - yyrestart() is a new action which can be used to restart
                     68:          the scanner after it has seen an end-of-file (a "real" one,
                     69:          that is, one for which yywrap() returned non-zero).  It takes
                     70:          a FILE* argument indicating a new file to scan and sets
                     71:          things up so that a subsequent call to yylex() will start
                     72:          scanning that file.
                     73: 
                     74:        - Internal scanner names all preceded by "yy_"
                     75: 
                     76:        - lex.yy.c is deleted if errors are encountered during processing.
                     77: 
                     78:        - Comments may be put in the first section of the input by preceding
                     79:          them with '#'.
                     80: 
                     81: 
                     82: 
                     83:     Other changes:
                     84: 
                     85:        - Some portability-related bugs fixed, in particular for machines
                     86:          with unsigned characters or sizeof( int* ) != sizeof( int ).
                     87:          Also, tweaks for VMS and Microsoft C (MS-DOS), and identifiers all
                     88:          trimmed to be 31 or fewer characters.  Shortened file names
                     89:          for dinosaur OS's.  Checks for allocating > 64K memory
                     90:          on 16 bit'ers.  Amiga tweaks.  Compiles using gcc on a Sun-3.
                     91: 
                     92:        - Compressed and fast scanner skeletons merged.
                     93: 
                     94:        - Skeleton header files done away with.
                     95: 
                     96:        - Generated scanner uses prototypes and "const" for __STDC__.
                     97: 
                     98:        - -DSV flag is now -DSYS_V for System V compilation.
                     99: 
                    100:        - Removed all references to FTL language.
                    101: 
                    102:        - Software now covered by BSD Copyright.
                    103: 
                    104:        - flex will replace lex in subsequent BSD releases.

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