(f)lex Regular Expression for C++ comment.

Just in case anyone needs them:
the C++ style comment: /* this comment */ // and this comment
in flex format (should improve scanner performance).
I never encountered it before, so I'll share it.


--- 8< ---- snip ---- 8< ---
%{ /* (f)lex specification */
%}
A [/]
B [*]
C [^/*]


%%


{A}({A}.*|{B}({A}|{C}|{B}+{C})*{B}+{A}) /* skip comment */
/*
  * {A}{B}({A}|{C}|{B}+{C})*{B}+{A} /* only C-style */
  */


--- 8< ---- snip ---- 8< ---


Regards,
Pieter Kuppens --- pwk@eb.ele.tue.nl
Eindhoven University of Technology --- EH 11.24 --- (+31)40-247 3394
E.S.V.V. Pusphaira on WWW; http://www2.stack.urc.tue.nl/Pusphaira/
[I strongly discourage attempts to handle comments this way, because they
fail as soon as a comment is longer than the token buffer. It's easy to do
this with exclusive start states, e.g.:


%x COMMENT
%%
"/*" begin COMMENT ;
<COMMENT>"*/" begin NORMAL;
<COMMENT>.|\n /* ignore */;


Eating // comments with "//".* is probably OK unless you're using AT&T lex with
its tiny fixed token buffer. -John]
-John]


--

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