Remove first and last items from array

Ruby
1

Hi,

I need to remove the first and last items in an array (which may have 1,
2 or more items so the resulting array after removal may be empty). I
came up with this:

a = [1,2,3,4,5]
2.times { a.pop; a.reverse! }

It works well, but do you think that there is a slightly less obscure
way!?

Cheers,

~ Mark

2

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi,

"pop"ing the first element of an Array is called “shift” (“unshift”
being the operation of adding one element
in front of the array).

a = [1,2,3,4,5]
a.pop; a.shift;

Florian G.

On Apr 8, 2008, at 6:30 PM, Mark D. wrote:

It works well, but do you think that there is a slightly less obscure
way!?

Cheers,

~ Mark

Posted via http://www.ruby-forum.com/.

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.8 (Darwin)

iEYEARECAAYFAkf7n7oACgkQJA/zY0IIRZbJgQCfclWSiv3lsOeSsBdFFMqWWTDE
aAIAoI0HoqSXrYbAhsMWRrYKp/Ngx/O0
=S3a0
-----END PGP SIGNATURE-----

3

On Apr 8, 2008, at 18:30 , Mark D. wrote:

I need to remove the first and last items in an array (which may
have 1,
2 or more items so the resulting array after removal may be empty). I
came up with this:

a = [1,2,3,4,5]
2.times { a.pop; a.reverse! }

Hehe.

I think the natural idiom is a slice:

a[1..-2]

It returns an array as long as a.length > 0.

– fxn

4

On Apr 8, 11:30 am, Mark D. [email protected] wrote:

way!?

Cheers,

~ Mark

Posted viahttp://www.ruby-forum.com/.

a.shift
a.pop
?

5

Thanks, can’t believe I didn’t think of the ‘shift’ operation! Oh well,
my crazy solution is quite funny I think…

~ Mark

6

a.shift
a.pop

This reads a little better to me.
You don’t want to collect the items at all right?

/Shawn

7

On 08.04.2008 18:56, Kyle S. wrote:

I think the natural idiom is a slice:

a[1…-2]

Slice works pretty well - unless the array is small:

irb(main):004:0> a=(1…5).to_a
=> [1, 2, 3, 4, 5]
irb(main):005:0> a.slice! 1…-1
=> [2, 3, 4]
irb(main):006:0> a=[]
=> []
irb(main):007:0> a.slice! 1…-1
=> nil
irb(main):008:0> a
=> [nil]
irb(main):009:0> a=[1]
=> [1]
irb(main):010:0> a.slice! 1…-1
=> []
irb(main):011:0>
irb(main):012:0* a
=> [1]

Kind regards

robert

8

In fact there is slice :slight_smile:
which takes the same args.
a.slice(1…-2)
and even a destructive
a.slice!(1…-2)
but for some reason my ruby really didn’t like it… so never mind the
destructive part…