--- Walnut <[EMAIL PROTECTED]> wrote:
> Suck the file into a single variable and:
>
> $entirefile =~ s!\/\*.*?\*\/!!g;
>
> >I am also very new to Perl! I need to figure out how I could skip a
> >block of comments in a C header file. For example, if I have something
> >like the following:
> >
> >/* This is my block of comments.....blah
> >...blah.....................................................................and
> >lots more comments here........
> >and then even more here!.................... with my end of comments
> >indentifier on the next line!.........
> >
> >*/
Well, better late than never:
The substitution "s!\/\*.*?\*\/!!g", while looking fine on the surface, has two
problems.
1. It doesn't account for false positives, such as comments in strings that shouldn't
be removed:
somevar = "/* I'm not a comment! */";
Admittedly, this is an unusual situation and not one that I lie awake at night
worrying about.
However, the second situation is far more common.
2. Oftimes, a programmer will comment out an entire chunk of code. If that code has
embedded
multi-line comments, the above substitution will also fail.
/*
multi /* bla */
line
comment
*/
Try the following snippet:
undef $/;
$_ = <DATA>;
s!\/\*.*?\*\/!!g;
print;
__DATA__
somevar = "/* I'm not a comment! */";
This
/*
multi /* bla */
line
comment
*/
is a sentence.
That will print:
somevar = "";
This
/*
multi
line
comment
*/
is a sentence.
Clearly, it's failing in both cases. Unfortunately, some would say that the cure is
worse than
the disease :) Here's the regex (from Mastering Regular Expressions, with a minor typo
corrected):
###########################
s{
# First, things we want to match and not throw away
(
[^"'/]+ # other stuff
| # - or -
(?:"[^"\\]*(?:\\.[^"\\]*)*" [^"'/]*)+ # double-quoted string
| # - or -
(?:'[^'\\]*(?:\\.[^'\\]*)*' [^"'/]*)+ # single-quoted string
)
| # or
/(?: # all comments start with a slash
\*[^*]*\*+(?:[^/*]|[^*]*\*+)*/ # traditional C comments
| # - or -
/[^\n]+ # C++ // -style comments
)
}{$1}gsx;
###########################
Running that monstrosity in the above program results in:
somevar = "/* I'm not a comment! */";
This
is a sentence.
Cheers,
Curtis Poe
=====
Senior Programmer
Onsite! Technology (http://www.onsitetech.com/)
"Ovid" on http://www.perlmonks.org/
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