Re: Implement new symbol-start and symbol-end regexp operators

[Jim Blandy]

Has anyone had a chance to try this patch out?

Jim Blandy <address@hidden> writes:

> Eli Zaretskii <address@hidden> writes:
> 
> > > From: Jim Blandy <address@hidden>
> > > Date: 04 May 2004 14:17:44 -0500
> > >   
> > > + @item \_<
> > > + @cindex @samp{\_<} in regexp
> > 
> > IMHO, an additional index entry here, something like
> > 
> >       @cindex matching symbols in regexp
> > 
> > would be useful.
> 
> Okay, I added:
> 
> + @cindex symbols, matching in regexp
> 
> 
> src/ChangeLog:
> 2004-04-29  Jim Blandy  <address@hidden>
> 
>       Add support for new '\_<' and '\_>' regexp operators, matching the
>       beginning and ends of symbols.
>       * regex.c (enum syntaxcode): Add Ssymbol.
>       (init_syntax_once): Set the syntax for '_' to Ssymbol, not Sword.
>       (symbeg, symend): New opcodes.
>       (print_partial_compiled_pattern): Print the new opcodes properly.
>       (regex_compile): Parse the new operators.
>       (analyze_first): symbeg and symend match only the empty string.
>       (mutually_exclusive_p): symend is mutually exclusive with \s_ and
>       \sw; symbeg is mutually exclusive with \S_ and \Sw.
>       (re_match_2_internal): Add code for symbeg and symend.
>       * search.c (trivial_regexp_p): \_ is no longer a trivial regexp.
> 
> man/ChangeLog:
> 2004-04-29  Jim Blandy  <address@hidden>
> 
>       * search.texi (Regexps): Document the \_< and \_> regexp operators.
> 
> lispref/ChangeLog:
> 2004-05-04  Jim Blandy  <address@hidden>
> 
>       * searching.texi (Regexp Backslash): Document new \_< and \_>
>       operators.
> 
> *** src/regex.c.~2~   2004-04-29 15:56:53.000000000 -0500
> --- src/regex.c       2004-04-29 17:44:24.000000000 -0500
> ***************
> *** 219,225 ****
>   /* Define the syntax stuff for \<, \>, etc.  */
>   
>   /* Sword must be nonzero for the wordchar pattern commands in re_match_2.  
> */
> ! enum syntaxcode { Swhitespace = 0, Sword = 1 };
>   
>   # ifdef SWITCH_ENUM_BUG
>   #  define SWITCH_ENUM_CAST(x) ((int)(x))
> --- 219,225 ----
>   /* Define the syntax stuff for \<, \>, etc.  */
>   
>   /* Sword must be nonzero for the wordchar pattern commands in re_match_2.  
> */
> ! enum syntaxcode { Swhitespace = 0, Sword = 1, Ssymbol = 2 };
>   
>   # ifdef SWITCH_ENUM_BUG
>   #  define SWITCH_ENUM_CAST(x) ((int)(x))
> ***************
> *** 399,405 ****
>        if (ISALNUM (c))
>       re_syntax_table[c] = Sword;
>   
> !    re_syntax_table['_'] = Sword;
>   
>      done = 1;
>   }
> --- 399,405 ----
>        if (ISALNUM (c))
>       re_syntax_table[c] = Sword;
>   
> !    re_syntax_table['_'] = Ssymbol;
>   
>      done = 1;
>   }
> ***************
> *** 656,661 ****
> --- 656,664 ----
>     wordbound,        /* Succeeds if at a word boundary.  */
>     notwordbound,     /* Succeeds if not at a word boundary.  */
>   
> +   symbeg,       /* Succeeds if at symbol beginning.  */
> +   symend,       /* Succeeds if at symbol end.  */
> + 
>       /* Matches any character whose syntax is specified.  Followed by
>          a byte which contains a syntax code, e.g., Sword.  */
>     syntaxspec,
> ***************
> *** 1095,1100 ****
> --- 1098,1110 ----
>       case wordend:
>         printf ("/wordend");
>   
> +     case symbeg:
> +       printf ("/symbeg");
> +       break;
> + 
> +     case symend:
> +       printf ("/symend");
> + 
>       case syntaxspec:
>         printf ("/syntaxspec");
>         mcnt = *p++;
> ***************
> *** 3135,3140 ****
> --- 3145,3163 ----
>             BUF_PUSH (wordend);
>             break;
>   
> +         case '_':
> +           if (syntax & RE_NO_GNU_OPS)
> +             goto normal_char;
> +               laststart = b;
> +               PATFETCH (c);
> +               if (c == '<')
> +                 BUF_PUSH (symbeg);
> +               else if (c == '>')
> +                 BUF_PUSH (symend);
> +               else
> +                 FREE_STACK_RETURN (REG_BADPAT);
> +               break;
> + 
>           case 'b':
>             if (syntax & RE_NO_GNU_OPS)
>               goto normal_char;
> ***************
> *** 3629,3634 ****
> --- 3652,3659 ----
>       case notwordbound:
>       case wordbeg:
>       case wordend:
> +     case symbeg:
> +     case symend:
>         continue;
>   
>   
> ***************
> *** 4396,4409 ****
>         break;
>   
>       case wordend:
> !     case notsyntaxspec:
>         return ((re_opcode_t) *p1 == syntaxspec
> !           && p1[1] == (op2 == wordend ? Sword : p2[1]));
>   
>       case wordbeg:
> !     case syntaxspec:
>         return ((re_opcode_t) *p1 == notsyntaxspec
> !           && p1[1] == (op2 == wordbeg ? Sword : p2[1]));
>   
>       case wordbound:
>         return (((re_opcode_t) *p1 == notsyntaxspec
> --- 4421,4440 ----
>         break;
>   
>       case wordend:
> !       return ((re_opcode_t) *p1 == syntaxspec && p1[1] == Sword);
> !     case symend:
>         return ((re_opcode_t) *p1 == syntaxspec
> !               && (p1[1] == Ssymbol || p1[1] == Sword));
> !     case notsyntaxspec:
> !       return ((re_opcode_t) *p1 == syntaxspec && p1[1] == p2[1]);
>   
>       case wordbeg:
> !       return ((re_opcode_t) *p1 == notsyntaxspec && p1[1] == Sword);
> !     case symbeg:
>         return ((re_opcode_t) *p1 == notsyntaxspec
> !               && (p1[1] == Ssymbol || p1[1] == Sword));
> !     case syntaxspec:
> !       return ((re_opcode_t) *p1 == notsyntaxspec && p1[1] == p2[1]);
>   
>       case wordbound:
>         return (((re_opcode_t) *p1 == notsyntaxspec
> ***************
> *** 5528,5533 ****
> --- 5559,5650 ----
>           }
>         break;
>   
> +     case symbeg:
> +       DEBUG_PRINT1 ("EXECUTING symbeg.\n");
> + 
> +       /* We FAIL in one of the following cases: */
> + 
> +       /* Case 1: D is at the end of string.  */
> +       if (AT_STRINGS_END (d))
> +         goto fail;
> +       else
> +         {
> +           /* C1 is the character before D, S1 is the syntax of C1, C2
> +              is the character at D, and S2 is the syntax of C2.  */
> +           re_wchar_t c1, c2;
> +           int s1, s2;
> + #ifdef emacs
> +           int offset = PTR_TO_OFFSET (d);
> +           int charpos = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
> +           UPDATE_SYNTAX_TABLE (charpos);
> + #endif
> +           PREFETCH ();
> +           c2 = RE_STRING_CHAR (d, dend - d);
> +           s2 = SYNTAX (c2);
> +     
> +           /* Case 2: S2 is neither Sword nor Ssymbol. */
> +           if (s2 != Sword && s2 != Ssymbol)
> +             goto fail;
> + 
> +           /* Case 3: D is not at the beginning of string ... */
> +           if (!AT_STRINGS_BEG (d))
> +             {
> +               GET_CHAR_BEFORE_2 (c1, d, string1, end1, string2, end2);
> + #ifdef emacs
> +               UPDATE_SYNTAX_TABLE_BACKWARD (charpos - 1);
> + #endif
> +               s1 = SYNTAX (c1);
> + 
> +               /* ... and S1 is Sword or Ssymbol.  */
> +               if (s1 == Sword || s1 == Ssymbol)
> +                 goto fail;
> +             }
> +         }
> +       break;
> + 
> +     case symend:
> +       DEBUG_PRINT1 ("EXECUTING symend.\n");
> + 
> +       /* We FAIL in one of the following cases: */
> + 
> +       /* Case 1: D is at the beginning of string.  */
> +       if (AT_STRINGS_BEG (d))
> +         goto fail;
> +       else
> +         {
> +           /* C1 is the character before D, S1 is the syntax of C1, C2
> +              is the character at D, and S2 is the syntax of C2.  */
> +           re_wchar_t c1, c2;
> +           int s1, s2;
> + #ifdef emacs
> +           int offset = PTR_TO_OFFSET (d) - 1;
> +           int charpos = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
> +           UPDATE_SYNTAX_TABLE (charpos);
> + #endif
> +           GET_CHAR_BEFORE_2 (c1, d, string1, end1, string2, end2);
> +           s1 = SYNTAX (c1);
> + 
> +           /* Case 2: S1 is neither Ssymbol nor Sword.  */
> +           if (s1 != Sword && s1 != Ssymbol)
> +             goto fail;
> + 
> +           /* Case 3: D is not at the end of string ... */
> +           if (!AT_STRINGS_END (d))
> +             {
> +               PREFETCH_NOLIMIT ();
> +               c2 = RE_STRING_CHAR (d, dend - d);
> + #ifdef emacs
> +               UPDATE_SYNTAX_TABLE_FORWARD (charpos);
> + #endif
> +               s2 = SYNTAX (c2);
> + 
> +               /* ... and S2 is Sword or Ssymbol.  */
> +               if (s2 == Sword || s2 == Ssymbol)
> +                     goto fail;
> +             }
> +         }
> +       break;
> + 
>       case syntaxspec:
>       case notsyntaxspec:
>         not = (re_opcode_t) *(p - 1) == notsyntaxspec;
> *** src/search.c.~1~  2002-05-12 19:04:16.000000000 -0500
> --- src/search.c      2004-04-29 17:30:17.000000000 -0500
> ***************
> *** 962,968 ****
>           {
>           case '|': case '(': case ')': case '`': case '\'': case 'b':
>           case 'B': case '<': case '>': case 'w': case 'W': case 's':
> !         case 'S': case '=': case '{': case '}':
>           case 'c': case 'C': /* for categoryspec and notcategoryspec */
>           case '1': case '2': case '3': case '4': case '5':
>           case '6': case '7': case '8': case '9':
> --- 962,968 ----
>           {
>           case '|': case '(': case ')': case '`': case '\'': case 'b':
>           case 'B': case '<': case '>': case 'w': case 'W': case 's':
> !         case 'S': case '=': case '{': case '}': case '_':
>           case 'c': case 'C': /* for categoryspec and notcategoryspec */
>           case '1': case '2': case '3': case '4': case '5':
>           case '6': case '7': case '8': case '9':
> *** man/search.texi.~1~       2002-07-06 08:44:06.000000000 -0500
> --- man/search.texi   2004-04-29 17:38:41.000000000 -0500
> ***************
> *** 672,677 ****
> --- 672,689 ----
>   @item \W
>   matches any character that is not a word-constituent.
>   
> + @item \_<
> + matches the empty string, but only at the beginning of a symbol.  A
> + symbol is a sequence of one or more word or symbol constituent
> + characters.  @samp{\_<} matches at the beginning of the buffer only if
> + a symbol-constituent character follows.
> + 
> + @item \_>
> + matches the empty string, but only at the end of a symbol.  A symbol
> + is a sequence of one or more word or symbol constituent characters.
> + @samp{\_>} matches at the end of the buffer only if the contents end
> + with a symbol-constituent character.
> + 
>   @item address@hidden
>   matches any character whose syntax is @var{c}.  Here @var{c} is a
>   character that designates a particular syntax class: thus, @samp{w}
> *** searching.texi.~1.48.~    2004-02-16 20:09:15.000000000 -0500
> --- searching.texi    2004-05-05 01:12:38.000000000 -0500
> ***************
> *** 666,671 ****
> --- 666,686 ----
>   with a word-constituent character.
>   @end table
>   
> + @item \_<
> + @cindex @samp{\_<} in regexp
> + @cindex symbols, matching in regexp
> + matches the empty string, but only at the beginning of a symbol.  A
> + symbol is a sequence of one or more word or symbol constituent
> + characters.  @samp{\_<} matches at the beginning of the buffer (or
> + string) only if a symbol-constituent character follows.
> + 
> + @item \_>
> + @cindex @samp{\_>} in regexp
> + matches the empty string, but only at the end of a symbol.  A symbol
> + is a sequence of one or more word or symbol constituent characters.
> + @samp{\_>} matches at the end of the buffer (or string) only if the
> + contents end with a symbol-constituent character.
> + 
>   @kindex invalid-regexp
>     Not every string is a valid regular expression.  For example, a string
>   with unbalanced square brackets is invalid (with a few exceptions, such
> *** etc/NEWS.~1.950.~ 2004-04-27 17:02:27.000000000 -0500
> --- etc/NEWS  2004-05-04 14:15:33.000000000 -0500
> ***************
> *** 90,95 ****
> --- 90,101 ----
>   
>   * Changes in Emacs 21.4
>   
> + +++
> + ** There are now two new regular expression operators, \_< and \_>,
> + for matching the beginning and end of a symbol.  A symbol is a
> + non-empty sequence of either word or symbol constituent characters, as
> + specified by the syntax table.
> + 
>   ---
>   ** The IELM prompt is now, by default, read-only.  This can be
>   controlled with the new user option `ielm-prompt-read-only'.