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Regular expression to match only strings NOT containing particular words

P: n/a
I can write a regular expression that will only match strings that are
NOT the word apple:

^([^a].*|a[^p].*|ap[^p].*|app[^l].*|apple.+)$

But is there a neater way, and how would I do it to match strings that
are NOT the word apple OR banana? Then what would be needed to match
only strings that do not CONTAIN the word "apple" or "banana" or
"cherry"?

I'd love it if the following worked:

^[^(apple)(banana)(cherry)]*$

But it appears the parantheses are ignored, as

^[(apple)(banana)(cherry)]*$

simply matches any string that consists entire of the characters
a,b,c,e,h,l,n,r,p & y.

Oct 19 '07 #1
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4 Replies


P: n/a
Dylan Nicholson wrote:
I can write a regular expression that will only match strings that are
NOT the word apple:

^([^a].*|a[^p].*|ap[^p].*|app[^l].*|apple.+)$

But is there a neater way, and how would I do it to match strings that
are NOT the word apple OR banana? Then what would be needed to match
only strings that do not CONTAIN the word "apple" or "banana" or
"cherry"?
!(/apple/ or /banana/ or /cherry/)

jue
Oct 19 '07 #2

P: n/a
2007-10-18, 22:00(-07), Dylan Nicholson:
I can write a regular expression that will only match strings that are
NOT the word apple:

^([^a].*|a[^p].*|ap[^p].*|app[^l].*|apple.+)$

But is there a neater way, and how would I do it to match strings that
are NOT the word apple OR banana? Then what would be needed to match
only strings that do not CONTAIN the word "apple" or "banana" or
"cherry"?

I'd love it if the following worked:

^[^(apple)(banana)(cherry)]*$

But it appears the parantheses are ignored, as

^[(apple)(banana)(cherry)]*$

simply matches any string that consists entire of the characters
a,b,c,e,h,l,n,r,p & y.
With perl regexps:

perl -ne 'print if /^(?:(?!apple|banana).)*$/'
or probably better:
perl -ne 'print if /^(?!.*(?:apple|banana))/'

But then, why not

perl -ne 'print if !/apple|banana/'

Note that vim's regexps have an equivalent negative look-ahead
operator.

--
Stéphane
Oct 19 '07 #3

P: n/a
On Thu, 18 Oct 2007 22:00:28 -0700, Dylan Nicholson
<wi******@hotmail.comwrote:
>I can write a regular expression that will only match strings that are
NOT the word apple:

^([^a].*|a[^p].*|ap[^p].*|app[^l].*|apple.+)$

But is there a neater way, and how would I do it to match strings that
are NOT the word apple OR banana? Then what would be needed to match
only strings that do not CONTAIN the word "apple" or "banana" or
"cherry"?

I'd love it if the following worked:

^[^(apple)(banana)(cherry)]*$

But it appears the parantheses are ignored, as

^[(apple)(banana)(cherry)]*$

simply matches any string that consists entire of the characters
a,b,c,e,h,l,n,r,p & y.
A simple way is to write the regex to match apple or banana or cherry,
do the match and then check the Success property of the match object.

Execute the following mini program

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
Regex r = new Regex(".*apple|banana|cherry.*");
string[] strings =
"apple,banana,cherry,applebanana,applebananacherry ,fishapple,chips,chip
and apple,apple pie".Split(',');
foreach (string s in strings)
{
Console.WriteLine("{0} Match? {1}", s,
r.Match(s).Success);
}
Console.ReadLine();
}
}
}

You should get this:

apple Match? True
banana Match? True
cherry Match? True
applebanana Match? True
applebananacherry Match? True
fishapple Match? True
chips Match? False
chip and apple Match? True
apple pie Match? True

--
http://bytes.thinkersroom.com
Oct 19 '07 #4

P: n/a
On Thu, 18 Oct 2007 22:00:28 -0700, Dylan Nicholson
<wi******@hotmail.comwrote:
>But is there a neater way, and how would I do it to match strings that
are NOT the word apple OR banana? Then what would be needed to match
only strings that do not CONTAIN the word "apple" or "banana" or
"cherry"?
The general answer is that you should use separate regexen and logical
operators, or an explicit !~ but the subject of negating regexen is
discussed to some depth in the following thread @ PM:

http://perlmonks.org/?node_id=588315
Michele
--
{$_=pack'B8'x25,unpack'A8'x32,$a^=sub{pop^pop}->(map substr
(($a||=join'',map--$|x$_,(unpack'w',unpack'u','G^<R<Y]*YB='
..'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,$_,
256),7,249);s/[^\w,]/ /g;$ \=/^J/?$/:"\r";print,redo}#JAPH,
Oct 19 '07 #5

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