Forum: Ruby String#split "feature"

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Gary Y. (Guest)
on 2009-02-10 22:21
(Received via mailing list)
Just got bitten by some functionality of split w/ grouped patterns:

(in ruby 1.8.6...)
>> "foo bar baz".split(/bar/)
=> ["foo ", " baz"]
>> "foo bar baz".split(/(bar)/)
=> ["foo ", "bar", " baz"]

The 1.8 docs are silent on this, but the 1.9 docs at least say
"If pattern contains groups, the respective matches will be returned in
the
array as well. "

This "feature" surprised the heck out of me..  Anyone know if this
functionality is intentional (from the enduser standpoint), or rather a
byproduct of implementation details?

Anyhoo, if anyone else gets weird behavior for string split including
the
pattern, or with groups in the pattern, maybe you'll remember this or
maybe
google will tell you about this.

Thanks,
-Gary
7stud -. (Guest)
on 2009-02-10 22:39
Gary Y. wrote:
>
> The 1.8 docs are silent on this, but the 1.9 docs at least say
> "If pattern contains groups, the respective matches will be returned in
> the
> array as well. "
>

pickaxe2 p.619:
=====
split
...
...
If pattern includes groups, these groups will be included in the
returned values.
...
=====


> This "feature" surprised the heck out of me..  Anyone know if this
> functionality is intentional (from the enduser standpoint), or rather a
> byproduct of implementation details?
>

It can be a really handy feature.  python's regex split() function works
the same way.


> Anyhoo, if anyone else gets weird behavior for string split including
> the
> pattern, or with groups in the pattern, maybe you'll remember this or
> maybe
> google will tell you about this.
>
> Thanks,
> -Gary
Rob B. (Guest)
on 2009-02-10 22:48
(Received via mailing list)
On Feb 10, 2009, at 3:38 PM, 7stud -- wrote:

> =====
> split
> ...
> ...
> If pattern includes groups, these groups will be included in the
> returned values.
> ...
> =====

Interestingly, this feature is described in String#scan, but the ri
docs for my Apple-provided ruby do not have the sentence for
String#split.

$ ruby -v
ruby 1.8.6 (2008-03-03 patchlevel 114) [universal-darwin9.0]

-Rob

>
>> Anyhoo, if anyone else gets weird behavior for string split including
>> the
>> pattern, or with groups in the pattern, maybe you'll remember this or
>> maybe
>> google will tell you about this.
>>
>> Thanks,
>> -Gary
>

Rob B.    http://agileconsultingllc.com
removed_email_address@domain.invalid
F. Senault (Guest)
on 2009-02-11 00:15
(Received via mailing list)
Le 10 février 2009 à 21:20, Gary Y. a écrit :

> This "feature" surprised the heck out of me..  Anyone know if this
> functionality is intentional (from the enduser standpoint), or rather a
> byproduct of implementation details?
>
> Anyhoo, if anyone else gets weird behavior for string split including the
> pattern, or with groups in the pattern, maybe you'll remember this or maybe
> google will tell you about this.

It's quite useful.  Note that you can always use non-capturing groups
(the (?:expr) construct) if you don't want them :

>> "one, two and three".split(/\s*(and|or|,)?\s+/)
=> ["one", ",", "two", "and", "three"]

>> "one, two and three".split(/\s*(?:and|or|,)?\s+/)
=> ["one", "two", "three"]

Fred
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