How to find multiple matches in a string

Ruby
1

I know how to use regular expressions to find the first match of a
pattern in a string. But, how do I most easily find multiple matches?
For example, if the string is

s = ‘abcde_abcde_abcde’

and I want to find the location of ALL the ‘b’ characters, how do I do
it? If I use

m = s.match(/b/)

then m.offset(0) => [1,2]

but I don’t have any information about the second or third occurences of
‘b’.

–Alex

2

Hei,

s = ‘abcde_abcde_abcde’
m = s.scan(/b/)
p m # [‘b’,‘b’,‘b’]

HTH

–
Andrea D.

3

On Apr 13, 12:51 pm, Alex DeCaria [email protected]
wrote:

I know how to use regular expressions to find the first match of a
pattern in a string. But, how do I most easily find multiple matches?
For example, if the string is

s = ‘abcde_abcde_abcde’

and I want to find the location of ALL the ‘b’ characters, how do I do
it?

Try #scan

4

On 04/13/2010 06:55 PM, Andrea D. wrote:

Hei,

s = ‘abcde_abcde_abcde’
m = s.scan(/b/)
p m # [‘b’,‘b’,‘b’]

Or even

s.scan(/b) {|match| p match}

Kind regards

robert

5

On Tue, Apr 13, 2010 at 7:01 PM, Alex DeCaria
[email protected] wrote:

Andrea D.
GitHub - bolthar/freightrain: Ruby desktop development made easy
http://usingimho.wordpress.com

Thanks Andrea. But is there a way to also find the locations (indexes)
of the ‘b’ characters?

Take a look at this thread, maybe you can get some ideas:

http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/337667

Jesus.

6

Andrea D. wrote:

Hei,

s = ‘abcde_abcde_abcde’
m = s.scan(/b/)
p m # [‘b’,‘b’,‘b’]

HTH

–
Andrea D.
GitHub - bolthar/freightrain: Ruby desktop development made easy
http://usingimho.wordpress.com

Thanks Andrea. But is there a way to also find the locations (indexes)
of the ‘b’ characters?

–Alex

7

On 4/13/10, Alex DeCaria [email protected] wrote:

of the ‘b’ characters?
I think this works:

s = ‘abcde_abcde_abcde’
i=0
while i=s.index(‘b’,i)
do_something_with i
end

8

Nope, tried it.

–
Andrea D.

9

string = “abcde abcde abcde”
sum = 0
result = []
blocks = string.split(/b/)
blocks.pop
blocks.each do |block|
sum += block.length
result << sum
sum += 1
end
p result # [1,7,13]

Don’t tell anyone I’ve written this crap :slight_smile:

–
Andrea D.

10

On 13.04.2010 19:01, Alex DeCaria wrote:

Andrea D. wrote:

Hei,

s = ‘abcde_abcde_abcde’
m = s.scan(/b/)
p m # [‘b’,‘b’,‘b’]

Thanks Andrea. But is there a way to also find the locations (indexes)
of the ‘b’ characters?

irb(main):012:0> s="a "*5
=> "a a a a a "
irb(main):013:0> s.scan(/a+/) { p $~, $~.offset(0) }
#<MatchData “a”>
[0, 1]
#<MatchData “a”>
[2, 3]
#<MatchData “a”>
[4, 5]
#<MatchData “a”>
[6, 7]
#<MatchData “a”>
[8, 9]
=> "a a a a a "
irb(main):014:0>

Kind regards

robert

11

On Wed, Apr 14, 2010 at 1:32 AM, Andrea D.
[email protected] wrote:

i=0
while i=s.index(‘b’,i)
do_something_with i
end

what do you mean it does not work?

btw, you can also use stringscan. it’s fast.

s=StringScanner.new “this is a test string”
=> #<StringScanner 0/21 @ “this …”>

p s.pos while s.scan_until /s/
4
7
13
16
=> nil

pls do not top post.

kind regards -botp