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Diffstat (limited to 'doc')
| -rw-r--r-- | doc/flex.texi | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/doc/flex.texi b/doc/flex.texi index f4ad42a..c8ec07f 100644 --- a/doc/flex.texi +++ b/doc/flex.texi @@ -746,6 +746,34 @@ the character with hexadecimal value 2a @item (r) match an @samp{r}; parentheses are used to override precedence (see below) +@item (?r-s:pattern) +apply option @samp{r} and omit option @samp{s} while interpreting pattern. +Options may be zero or more of the characters @samp{i}, @samp{s}, or @samp{x}. + +@samp{i} means case-insensitive. @samp{-i} means case-sensitive. + +@samp{s} alters the meaning of the @samp{.} syntax to match any single byte whatsoever. +@samp{-s} alters the meaning of @samp{.} to match any byte except @samp{\n}. + +@samp{x} ignores comments and whitespace in patterns. Whitespace is ignored unless +it is backslash-escaped, contained within @samp{""}s, or appears inside a +character class. TODO -- Do we ignore Perl comments, C comments, or both? + +The following are all valid: + +@verbatim +(?:foo) same as (foo) +(?i:ab7) same as ([aA][bB]7) +(?-i:ab) same as (ab) +(?s:.) same as [\x00-\xFF] +(?-s:.) same as [^\n] +(?ix-s: a . b) same as ([Aa][^\n][bB]) +(?x:a b) same as ("ab") +(?x:a\ b) same as ("a b") +(?x:a" "b) same as ("a b") +(?x:a[ ]b) same as ("a b") +@end verbatim + @item (?# comment ) omit everything within @samp{()}. The first @samp{)} character encountered ends the pattern. It is not possible to for the comment |