Feature #21284: Request: add `Array#pad` method

• Status: Open
• Assignee: -
• Target version: -

[MatzFan (Brian Cohen)]

A method to pad an array of arbitrary length with objects up to a specified array size does not currently exist.

Array#fill does not do this and I therefore propose the following method:

class Array
  def pad(pad_to_length, object = nil)
    fill(object, size, pad_to_length - size)
  end
end

I have provided an answer to a Stack Overflow question asking how this can be done in Ruby. I've also explained in a comment on the answer which suggests using Array#fill why this does not meet the exact need.

[nobu (Nobuyoshi Nakada)]

It may be possible with Array#fill and start-exclusive range?

ary.fill(object, -1^..padding_length)

[MatzFan (Brian Cohen)]

When I try and run that code, e.g.

[1, 2, 3].fill(nil, -1^..10)

'Integer#^': Range can't be coerced into Integer (TypeError)

In any case pad(10) is much prettier IMHO.

[nobu (Nobuyoshi Nakada)]

Current Ruby doesn't have start-exclusive range.
^.. is so-called neko-operator in Perl 6, and just this request reminded me of it, sorry.

[MatzFan (Brian Cohen)]

No worries, I thought it was some new syntax I was not aware of!

[matheusrich (Matheus Richard)]

What should happen if the size is smaller than what currently set?

[MatzFan (Brian Cohen)]

What should happen if the size is smaller than what currently set?

If the pad_to_length argument is less than or equal to the array's current size the array is returned unchanged. If it is larger, elements of the specified kind are pushed to the array until it reaches pad_to_length size and the modified array returned.