'#' characters are breaking my regexp

Ruby
1

I’m trying to build a regexp that includes music notes, eg Bb or C#.
However, the ‘#’ character is breaking them - basically it just stops
reading the string as soon as it gets to a #:

string = “(Ab|Bb|Db|Eb|Gb|A#|C#|D#|F#|G#|A|B|C|D|E|F|G)”
=> “(Ab|Bb|Db|Eb|Gb|A#|C#|D#|F#|G#|A|B|C|D|E|F|G)”

regex = Regexp.new(string)
=> AbBbDbEbGbA

Can anyone explain why this is happening and how to get around it? Is
it thinking that the part after the first hash is a comment for example?

thanks, max

2

Max,

I’m trying to build a regexp that includes music notes, eg Bb or C#.
However, the ‘#’ character is breaking them - basically it just stops
reading the string as soon as it gets to a #:

string = “(Ab|Bb|Db|Eb|Gb|A#|C#|D#|F#|G#|A|B|C|D|E|F|G)”
=> “(Ab|Bb|Db|Eb|Gb|A#|C#|D#|F#|G#|A|B|C|D|E|F|G)”
regex = Regexp.new(string)
=> AbBbDbEbGbA

Strange… it works for me:

string = “(Ab|Bb|Db|Eb|Gb|A#|C#|D#|F#|G#|A|B|C|D|E|F|G)”
=> “(Ab|Bb|Db|Eb|Gb|A#|C#|D#|F#|G#|A|B|C|D|E|F|G)”
/#{string}/
=> /(Ab|Bb|Db|Eb|Gb|A#|C#|D#|F#|G#|A|B|C|D|E|F|G)/
Regexp.new(string)
=> /(Ab|Bb|Db|Eb|Gb|A#|C#|D#|F#|G#|A|B|C|D|E|F|G)/

what’s your Ruby version?

as far as I can remember, # should have no special meaning (unless
followed by a { when it is an interpolation ) so I am not sure what’s
going on…

Cheers,
Peter

http://www.rubyrailways.com

3

Hi Peter. We’re still on 1.8.6 round here.

4

On 2008.11.13., at 13:11, Max W. wrote:

Hi Peter. We’re still on 1.8.6 round here.

Well, me too… I have no idea then. Let’s hope someone came across
this already and will help out.

Cheers,
Peter

http://www.rubyrailways.com

5

Peter S. wrote:

On 2008.11.13., at 13:11, Max W. wrote:

Hi Peter. We’re still on 1.8.6 round here.

Well, me too… I have no idea then. Let’s hope someone came across
this already and will help out.

Cheers,
Peter

http://www.rubyrailways.com

Bugger. How annoying…maybe i have some weird gem interference or
something. (facets perhaps). Don’t know how to debug that…

Anyone else?

Thanks!
max

6

Michael L. wrote:

On Thu, Nov 13, 2008 at 5:21 AM, Max W.
[email protected] wrote:

it thinking that the part after the first hash is a comment for example?
The # must be confusing the parser into thinking some #{} style
interpolation is going to happen.

Substitute # for # and see if that helps. Either way works the same
for me in 1.8.7.

-Michael L.

I tried that already, no joy :frowning:

string = “abc#def”
=> “abc#def”
/#{string}/
=> abc
string = “abc#def”
=> “abc#def”
/#{string}/
=> abc
Regexp.new(string)
=> abc

7

On Thu, Nov 13, 2008 at 5:21 AM, Max W.
[email protected] wrote:

it thinking that the part after the first hash is a comment for example?
The # must be confusing the parser into thinking some #{} style
interpolation is going to happen.

Substitute # for # and see if that helps. Either way works the same
for me in 1.8.7.

-Michael L.

8

string = “abc#def”
=> “abc#def”

/#{string}/
=> abc

string = “abc#def”

“abc\#def”

When you mash like /#{string}/, the inserted item is not treated as a
literal string, but as a fragment of Regexp notation. So either first
call
Regexp.escape(string) on it, or make it a valid regexp.

Next, “” might interpret # as an escape in string notation, so escape
that with \#.

And I always use ‘’ unless I need the special powers of a “”. So
‘abc#def’
will work, because ‘’ refrains from escaping anything that it doesn’t
need
to.

9

Max W. wrote:

Bugger. How annoying…maybe i have some weird gem interference or
something. (facets perhaps). Don’t know how to debug that…

  1. Run plain irb, don’t load any libraries yet,
  2. Try the example from the command line, see if it works.
  3. If it does, start loading libraries until it breaks.

From the prompt, it looks to me like you’re using script/console in
Rails, so you’ll have all the Rails stuff loaded too, like
ActiveSupport. But that doesn’t cause this problem for me:

$ script/console
Loading development environment (Rails 2.1.2)

string = “(Ab|Bb|Db|Eb|Gb|A#|C#|D#|F#|G#|A|B|C|D|E|F|G)”
=> “(Ab|Bb|Db|Eb|Gb|A#|C#|D#|F#|G#|A|B|C|D|E|F|G)”

regex = Regexp.new(string)
=> /(Ab|Bb|Db|Eb|Gb|A#|C#|D#|F#|G#|A|B|C|D|E|F|G)/

Nor facets:

require ‘facets’
=> []

regex = Regexp.new(string)
=> /(Ab|Bb|Db|Eb|Gb|A#|C#|D#|F#|G#|A|B|C|D|E|F|G)/

10

And it works fine on our server…it’s just on mine and my colleagues’
local machines that it doesn’t work. Aiiieeeee…

11

Phlip wrote:

“abc\#def”

When you mash like /#{string}/, the inserted item is not treated as a
literal string, but as a fragment of Regexp notation. So either first
call
Regexp.escape(string) on it, or make it a valid regexp.

Next, “” might interpret # as an escape in string notation, so escape
that with \#.

And I always use ‘’ unless I need the special powers of a “”. So
‘abc#def’
will work, because ‘’ refrains from escaping anything that it doesn’t
need
to.

Still no joy i’m afraid:

string = ‘abc#def’
=> “abc#def”

/#{string}/
=> abc

Regexp.escape(string)
=> “abc\#def”

Regexp.new(Regexp.escape(string))
=> abc

12

Le 13 novembre à 13:52, Max W. a écrit :

string = “abc#def”
=> “abc#def”

/#{string}/
=> abc

string = “abc#def”
=> “abc#def”

/#{string}/
=> abc

Regexp.new(string)
=> abc

Are you sure it’s not simply a display problem in IRB ?

s = “abc#def”
=> “abc#def”

re = /#{s}/
=> abc

re.inspect
=> “/abc#def/”

re.match(“aaaabc#defffff”)
=> #MatchData:0xca0ee0

re.match(“aaaabc#defffff”)[0]
=> “abc#def”

After a few tests, it seems it comes from wirble, in my case…

Fred

13

F. Senault wrote:

Are you sure it’s not simply a display problem in IRB ?

s = “abc#def”
=> “abc#def”

re = /#{s}/
=> abc

re.inspect
=> “/abc#def/”

re.match(“aaaabc#defffff”)
=> #MatchData:0xca0ee0

re.match(“aaaabc#defffff”)[0]
=> “abc#def”

After a few tests, it seems it comes from wirble, in my case…

Fred

That’s it exactly! Fred, you’re a genius - it was working properly all
along, it just looked like it wasn’t.

Thanks a lot, and to everyone else too.

14

On Nov 13, 2008, at 5:34 AM, Peter S. wrote:

as far as I can remember, # should have no special meaning (unless
followed by a { when it is an interpolation )

also becomes a comment character inside a Regexp if the /x

(EXTENDED) mode is used.

James Edward G. II