Forum: Ruby Regular Expression question

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Al C. (Guest)
on 2007-06-30 06:31
Hello,

Im working with regular expressions and I cant quite understand how the
"13" is extracted from the string.


Here is the irb output:
irb(main):005:0> "(13)"[1..-2].to_i
=> 13


I dont understadn how the [1..-2] parameter removes the parenthases from
the string.


Could someone please explain.

Thanks in advance.
unknown (Guest)
on 2007-06-30 06:42
(Received via mailing list)
In message <removed_email_address@domain.invalid>, Al Cholic
writes:
>Im working with regular expressions and I cant quite understand how the
>"13" is extracted from the string.
>Here is the irb output:
>irb(main):005:0> "(13)"[1..-2].to_i
>=> 13
>I dont understadn how the [1..-2] parameter removes the parenthases from
>the string.

"(13)"[0] = "("
"(13)"[1] = "1"
"(13)"[2] = "3"
"(13)"[3] = ")"

"(13)"[-1] = ")"
"(13)"[-2] = "3"
"(13)"[-3] = "1"
"(13)"[-4] = "("

"-N" counts from the end, starting with -1.

-2 is the character just before the end (the 3).  1 is the character
just after
the beginning (the 1).

From "just after the beginning" to "just before the end" is the string
without
the parentheses.

However, I must correct you:  You are not working with regular
expressions.
There are no regular expressions here, only array slices.

-s
Al C. (Guest)
on 2007-06-30 06:50
> "(13)"[0] = "("
> "(13)"[1] = "1"
> "(13)"[2] = "3"
> "(13)"[3] = ")"
>
> "(13)"[-1] = ")"
> "(13)"[-2] = "3"
> "(13)"[-3] = "1"
> "(13)"[-4] = "("
>
> "-N" counts from the end, starting with -1.


Thanks.  An the .. in [1..-2] means "keep everything in between" ?
unknown (Guest)
on 2007-06-30 06:56
(Received via mailing list)
In message <removed_email_address@domain.invalid>, Al Cholic
writes:
>Thanks.  An the .. in [1..-2] means "keep everything in between" ?

Right.

So, "hello, world!"[1..-2] => "ello, world"

-s
Al C. (Guest)
on 2007-06-30 07:02
unknown wrote:
> In message <removed_email_address@domain.invalid>, Al Cholic
> writes:
>>Thanks.  An the .. in [1..-2] means "keep everything in between" ?
>
> Right.
>
> So, "hello, world!"[1..-2] => "ello, world"
>
> -s


Thank you very much.
Robert D. (Guest)
on 2007-06-30 11:34
(Received via mailing list)
On 6/30/07, Peter S. <removed_email_address@domain.invalid> wrote:
> "(13)"[1] = "1"
> "(13)"[2] = "3"
> "(13)"[3] = ")"
>
> "(13)"[-1] = ")"
> "(13)"[-2] = "3"
> "(13)"[-3] = "1"
> "(13)"[-4] = "("
Maybe it would not hurt to add a little clarification, albeit the fact
that your didactic simplification has worked very well :). Especially
as this concerns a FAQ

In reality
"(13)"[0] => ?( which equals 40
and
"(13)"[0..0] => "("

Cheers
Robert
unknown (Guest)
on 2007-06-30 11:41
(Received via mailing list)
In message
<removed_email_address@domain.invalid>, "Robert
Dober" writes
:
>Maybe it would not hurt to add a little clarification, albeit the fact
>that your didactic simplification has worked very well :). Especially
>as this concerns a FAQ

Oops, doh!

You are correct, of course.

-s
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