In article <3E91974E.7000903 / uranus.dti.ne.jp>,
  Kazuo Saito <ksaito / uranus.dti.ne.jp> writes:

> 1) '[' and ']' must be escaped by '\' when they appear as a literal
>    in character class expressions.  /[[]]/ should be coded as /[\[\]]/
>    for example.

No.  What should be coed as /[\[\]]/ is /[][]/.

Or, /[[]]/ should be coded as /[\[]\]/

> 2) A literal '-' in a character class should be escaped too if the 
>    class has other '-' literals for range representation.  For instance, 
>    /[abcd-f-hijk]/ and /[--abc]/ should be written as 
>    /[abcd-f\-hijk]/ (or /[abcd\-f-hijk]/) and /[\--abc]/.
>    You can use '-' without '\' if the class has no ranges, like
>    /[-abc]/ or /[^-]/.

No.  `"-" at top or bottom of character class' will not warned except
for /[--abc]/ and /[abc--]/.  However the definition of `top' is bit
different between mine and matz's.

So /[a-zA-Z0-9.-]/ will not be warned.
-- 
Tanaka Akira