Regular Expression question

[Al Cholic]

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.

 

[Al Cholic]

"(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" ?

 

[Al Cholic]

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 Dober]

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] = "("

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