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Need help in forming a regular expression using regex_replace

 
 
deepak_kamath_n@yahoo.co.in
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      07-11-2006
Hello,

I am relatively new to the world of regex and require some help in
forming a regular expression to achieve the following:

I have an input stream similar to:

Slot: slot1
Description: this is a description
Slot: slot2
Description: this is the second description
Attribute1: atrra
Attribute2: attrb
Slot: slot3
Description: this is the third description
Attribute1: atrrc
Attribute2: attrd

I have to pick all the values for "Slot" and corresponding
"Attribute2". If there is no "Attribute2" for a "Slot", I need to skip
that Slot.

I arrived at a regular exp similar to:
"^Slot:\\s+(.*?)\\s+Description:\\s+.*?\\s+Attribu te1:\\s+.*?\\s+Attribute2:\\s+(.*?)\\s+.*?$"
but no luck. For the above example, this gives me "slot1 and attrd",
wheras I was expecting slot2, attrb and slot3, attrd.

Any thoughts on this is highly appreciated.

Thanks in advance!

Regards,
Deepak

 
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Robbie Hatley
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      07-11-2006
<(E-Mail Removed)> wrote:

> I am relatively new to the world of regex and require some help in
> forming a regular expression...


This has absolutely nothing to do with C++. Ask this in a group
that deals more with regexes, like a Gnu utilities group, or
even a perl group:

gnu.utils.help
comp.lang.perl.misc

Also be aware that many programs that use regexes use non-standard
extensions. What program are you using your regexes with? Ask in
a group suitable for that program. Or call it's vendor on the phone.
Or visit the program's web site. Or read a book or manual on the
program. Or google for info on the program.

--
Cheers,
Robbie Hatley
East Tustin, CA, USA
lone wolf intj at pac bell dot net
(put "[usenet]" in subject to bypass spam filter)
http://home.pacbell.net/earnur/


 
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mlimber
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      07-11-2006

Robbie Hatley wrote:
> <(E-Mail Removed)> wrote:
>
> > I am relatively new to the world of regex and require some help in
> > forming a regular expression...

>
> This has absolutely nothing to do with C++. Ask this in a group
> that deals more with regexes, like a Gnu utilities group, or
> even a perl group:
>
> gnu.utils.help
> comp.lang.perl.misc
>
> Also be aware that many programs that use regexes use non-standard
> extensions. What program are you using your regexes with? Ask in
> a group suitable for that program. Or call it's vendor on the phone.
> Or visit the program's web site. Or read a book or manual on the
> program. Or google for info on the program.


Not so! This group's stated subject matter is that which is related to
"the C++ language definition as determined by the ISO/ANSI C++ Standard
document, and by planned extensions and adjustments." In fact, TR1 (a
planned extension to the standard library) has a regex component.

Cheers! --M

 
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mlimber
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Posts: n/a
 
      07-11-2006
http://www.velocityreviews.com/forums/(E-Mail Removed) wrote:
> I am relatively new to the world of regex and require some help in
> forming a regular expression to achieve the following:
>
> I have an input stream similar to:
>
> Slot: slot1
> Description: this is a description
> Slot: slot2
> Description: this is the second description
> Attribute1: atrra
> Attribute2: attrb
> Slot: slot3
> Description: this is the third description
> Attribute1: atrrc
> Attribute2: attrd
>
> I have to pick all the values for "Slot" and corresponding
> "Attribute2". If there is no "Attribute2" for a "Slot", I need to skip
> that Slot.
>
> I arrived at a regular exp similar to:
> "^Slot:\\s+(.*?)\\s+Description:\\s+.*?\\s+Attribu te1:\\s+.*?\\s+Attribute2:\\s+(.*?)\\s+.*?$"
> but no luck. For the above example, this gives me "slot1 and attrd",
> wheras I was expecting slot2, attrb and slot3, attrd.
>
> Any thoughts on this is highly appreciated.


Can you show us a minimal but complete sample that demonstrates this
behavior? Your regular expression might be fine but your use of the
library might be in error.

Cheers! --M

 
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David Harmon
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      07-11-2006
On 11 Jul 2006 04:08:29 -0700 in comp.lang.c++,
(E-Mail Removed) wrote,
>I arrived at a regular exp similar to:
>"^Slot:\\s+(.*?)\\s+Description:\\s+.*?\\s+Attrib ute1:\\s+.*?\\s+Attribute2:\\s+(.*?)\\s+.*?$"
>but no luck. For the above example, this gives me "slot1 and attrd",
>wheras I was expecting slot2, attrb and slot3, attrd.
>
>Any thoughts on this is highly appreciated.


My thoughts: your regex is too complex and troublesome for me.

Read your input line-by-line into a std::string with std::getline.
If you like regex, use it to parse the lines,
"([A-Za-z0-9]).*)" or suchlike.

When you have parts you can handle them sensibly, errors are not all
the same "regex failed" message to the poor user, etc.

 
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Pete Becker
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Posts: n/a
 
      07-11-2006
(E-Mail Removed) wrote:

> Hello,
>
> I am relatively new to the world of regex and require some help in
> forming a regular expression to achieve the following:
>
> I have an input stream similar to:
>
> Slot: slot1
> Description: this is a description
> Slot: slot2
> Description: this is the second description
> Attribute1: atrra
> Attribute2: attrb
> Slot: slot3
> Description: this is the third description
> Attribute1: atrrc
> Attribute2: attrd
>
> I have to pick all the values for "Slot" and corresponding
> "Attribute2". If there is no "Attribute2" for a "Slot", I need to skip
> that Slot.
>
> I arrived at a regular exp similar to:
> "^Slot:\\s+(.*?)\\s+Description:\\s+.*?\\s+Attribu te1:\\s+.*?\\s+Attribute2:\\s+(.*?)\\s+.*?$"
> but no luck. For the above example, this gives me "slot1 and attrd",
> wheras I was expecting slot2, attrb and slot3, attrd.
>
> Any thoughts on this is highly appreciated.
>


As written, the regular expression requires the presence of all three of
Definition, Attribute1, and Attribute2 for a match. So with your
example, the Definition portion of the first Slot swallows all the input
up to Attribute1, that is, the definition field includes the beginnning
of the text for the next Slot.

You need to make the attributes optional. Change

"Attribute1:\\s+.*?\\s+"
to

"(?:Attribute1:\\s+.*?)?"

and similarly for attribute2. (Also take out the ^ an $; they're just
confusing the issue) That way you can pick out the first slot
definition. Then check whether it had an attribute 2, and if not, repeat
the search, starting at the first character after the match. In general
that kind of repetitive search is tricky to get right, so you're better
off letting the implementor handle the details. With TR1's regular
expressions, the code would look something like this:

using namespace std::tr1;

regex rgx( regular expression goes here );
const char *text = sample text goes here;
cregex_iterator first(text, text + strlen(text), rgx);
cregex_iterator last;
while (first != last)
{
if ((*first)[1].matched)
cout << *first << '\n';
++first;
}

For more details, see chapter 19 of my book, "The C++ Standard Library
Extensions," which will be in bookstores later this month. It covers all
of TR1.
 
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Robbie Hatley
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Posts: n/a
 
      07-14-2006

"mlimber" <(E-Mail Removed)> wrote:

> Robbie Hatley wrote:
> > <(E-Mail Removed)> wrote:
> >
> > > I am relatively new to the world of regex and require some help in
> > > forming a regular expression...

> >
> > This has absolutely nothing to do with C++. Ask this in a group
> > that deals more with regexes, like a Gnu utilities group, or
> > even a perl group:
> >
> > gnu.utils.help
> > comp.lang.perl.misc
> >
> > Also be aware that many programs that use regexes use non-standard
> > extensions. What program are you using your regexes with? Ask in
> > a group suitable for that program. Or call it's vendor on the phone.
> > Or visit the program's web site. Or read a book or manual on the
> > program. Or google for info on the program.

>
> Not so! ... TR1 (a planned extension to the standard library)
> has a regex component.


If so, awesome, bitchin', and cool. I had to write my own regex
routines (partly based a couple of non-standard, buggy regex
functions that come with my compiler) in order to do regexes in
my programs. It was a lot of hard work, doesn't always work right,
and is very unportable. If regex gets in the std. lib., that would
be awesome.

So perhaps I erred in my earlier comments. If so, my apologies
to you and the OP.


--
Cheers,
Robbie Hatley
East Tustin, CA, USA
lone wolf intj at pac bell dot net
(put "[usenet]" in subject to bypass spam filter)
http://home.pacbell.net/earnur/


 
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