Regular expression woes

[Mark (News)]

I'm not really sure where to post this question as it covers so many
platforms, but as the platform isn't relevant, here goes...

I'm trying to (pulling my hair out more like) construct a regular
expression string that says the following: "match if the input string
does not start with the characters http". E.g.

e.g.
"this string" - match
"this http string" - match
"http-and-a-bit-more-text" - no match
"ht" - match
"" - match

I've tried something like ^[^(^http)] but this gives no match on the
last 2. Any ideas? - I'd really appreciate it!
Cheers
Mark

[Paul Lalli]

"Mark (News)" <ne**@mail.adsl 4less.com> wrote in message
news:11******** *************@c 13g2000cwb.goog legroups.com...

I'm not really sure where to post this question as it covers so many
platforms, but as the platform isn't relevant, here goes...

Incorrect. The platform is exceedingly relevant. Regular expressions
are not a constant across languages. Perl regular expression are not
the same as Javascript regular expressions are not the same as PHP
regular expressions.

Choose one or the other, tell us what you're *trying* to do, and in what
environment you're doing it, and then someone can help you.

Paul Lalli

[Leendert Bottelberghs]

On Fri, 04 Feb 2005 07:19:44 -0800, Mark (News) wrote:

I'm trying to (pulling my hair out more like) construct a regular
expression string that says the following: "match if the input string
does not start with the characters http". E.g.

e.g.
"this string" - match
"this http string" - match
"http-and-a-bit-more-text" - no match
"ht" - match
"" - match

So don't match if the string starts with "http":

$str !~ m/^http/
-leendert bottelberghs

[ioneabu]

Mark (News) wrote:

I'm not really sure where to post this question as it covers so many
platforms, but as the platform isn't relevant, here goes...

I'm trying to (pulling my hair out more like) construct a regular
expression string that says the following: "match if the input string
does not start with the characters http". E.g.

wouldn't it be:

$match !~ m/^http/;

Is there an equivalent negation metacharacter for a word and not just a
character class? I was just wondering about that.

wana

[Chris Mattern]

Mark (News) wrote:

I'm not really sure where to post this question as it covers so many
platforms, but as the platform isn't relevant, here goes...

I'm trying to (pulling my hair out more like) construct a regular
expression string that says the following: "match if the input string
does not start with the characters http". E.g.

e.g.
"this string" - match
"this http string" - match
"http-and-a-bit-more-text" - no match
"ht" - match
"" - match

I've tried something like ^[^(^http)] but this gives no match on the
last 2. Any ideas? - I'd really appreciate it!
Cheers
Mark

Use the "does not match" operator, !~.

if ($my_string !~ /^http/) {
do_something(); }

If you're not using perl, well I guess your platform *is* relevant...
--
Christopher Mattern

"Which one you figure tracked us?"
"The ugly one, sir."
"...Could you be more specific?"

[Sherm Pendley]

Paul Lalli wrote:

Incorrect. The platform is exceedingly relevant. Regular expressions
are not a constant across languages. Perl regular expression are not
the same as Javascript regular expressions are not the same as PHP
regular expressions.

Also, what you're trying to do - negate a match condition - is often easier
to do in the host language than in the regex itself. For example, in Perl
you could do what you asked with this:

if ($some_string !~ /^http/) { ... }
# or
unless (/^http/) { ... }

But that just reinforces Paul's point - the platform is very relevant.

sherm--

--
Cocoa programming in Perl: http://camelbones.sourceforge.net
Hire me! My resume: http://www.dot-app.org

[Mark (News)]

I appreciate all the effort in providing a solution to the wider
problem, but perhaps I should have been more explicit - my fault.

I'm specifically trying to avoid using the host shell to do the
negation even though I can use this approach in just about any
language. What I'm really after is to contain the logic entirely within
the regular expression.

Why? Intellectual exercise. :-) (Kind of like why people climb
mountains, but without having to take my butt off the chair.)

Cheers
Mark

[Evertjan.]

Mark (News) wrote on 04 feb 2005 in comp.lang.javas cript:

I'm not really sure where to post this question as it covers so many
platforms, but as the platform isn't relevant, here goes...

I'm trying to (pulling my hair out more like) construct a regular
expression string that says the following: "match if the input string
does not start with the characters http". E.g.

e.g.
"this string" - match
"this http string" - match
"http-and-a-bit-more-text" - no match
"ht" - match
"" - match

In javascript this function is not match but test:

var s = "this http string"

if (!/^http/.test(s))
alert("Match!")
else
alert("No match!")

--
Evertjan.
The Netherlands.
(Replace all crosses with dots in my emailaddress)

[Rasto Levrinc]

Mark (News) wrote:

I appreciate all the effort in providing a solution to the wider
problem, but perhaps I should have been more explicit - my fault.

I'm specifically trying to avoid using the host shell to do the
negation even though I can use this approach in just about any
language. What I'm really after is to contain the logic entirely within
the regular expression.

You can do it with a zero-width negative look-ahead assertion in perl.

$string=~/^(?!http)/

--

Rasto Levrinc
http://sourceforge.net/projects/rlocate/

[Mark (News)]

Wow - quite brilliant!

Clearly this was far too easy for you. :-)

Cheers
Mark