String of int and range to array of int (Looking for improvement)

Question

First, what I have:

s = "1,3..5,8"

What I want:

["1", "3", "4", "5", "8"]

I found a way with as below

r = s.split(/\s?,\s?/)
=> ["10", "12..15", "17", "
r.map do |c|
  if Fixnum === eval(c)
    c
  else
    eval(c).map(&:to_s).flatten
  end
end
=> ["10", "12", "13", "14", "15", "17", "18"]

Would there be a better way to achieve this?

Jakobinsky · Accepted Answer · 2012-04-11 09:53:48Z

4

I wouldn't use eval.

A marginally better way would be:

s = "1,3...5,8"
p s.split(',').map { |n|
  if n.scan('...').empty?
    n
  else
    Range.new(*n.split('...', 2)).to_a
  end
}.flatten
# => ["1", "3", "4", "5", "8"]

EDIT: Fixed the code as suggested by @fl00r to work with multiple digit numbers.

edited Apr 11, 2012 at 9:53

answered Apr 11, 2012 at 8:21

Jakobinsky

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4 Comments

Benoît Over a year ago

Why would not you use eval? Is there a reason for this or just a personal way of doing it?

Jakobinsky Over a year ago

see the following question: stackoverflow.com/questions/1902744/…

fl00r Over a year ago

what if numbers are two digits? s=1,3...5,8,11? And what if ranges are two-dotted and three-dotted? s=1..3, 5...7, 20

Jakobinsky Over a year ago

good catch @fl00r, thanks. Regarding the number of dots, the original question asked for two.

fl00r · Accepted Answer · 2012-04-11 09:11:02Z

2

def magick(str)
  str.split(",").map do |item|
    item.scan(/(\d+)(\.+)(\d+)/)
    if $1
      Range.new($1.to_i, $3.to_i, $2 == "...").to_a
    else
      item.to_i
    end
  end.flatten
end

s1 = "1,3..5,8"
s2 = "1,3...5,8,20,100, 135"
magick(s1)
#=> [1, 3, 4, 5, 8]
magick(s2)
#=> [1, 3, 4, 8, 20, 100, 135]

answered Apr 11, 2012 at 9:11

fl00r

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Comments

peter · Accepted Answer · 2012-04-11 09:51:15Z

1

s = "10,12...15,17" 
s.split(',').map { |n| n['...'] ? Range.new(*n.split('...', 2)).to_a : n}.flatten 
#=> ["10", "12", "13", "14", "15", "17"]

answered Apr 11, 2012 at 9:51

peter

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2 Comments

fl00r Over a year ago

12...15 in Ruby shouldn't return 15

Jakobinsky Over a year ago

@fl00r true but the original question was written with three-dots and expected to return 15.

DaveShaw · Accepted Answer · 2012-04-12 10:16:45Z

0

How about this way:

s='1,2..6,10'

s.split(',').map { |e| e.strip.include?('..') ? eval("(#{e}).to_a") : e.to_i }.flatten

edited Apr 12, 2012 at 10:16

DaveShaw

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answered Apr 11, 2012 at 11:41

Jon Snow

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1 Comment

peter Over a year ago

i also program in javascript and there eval is evil, don't know about ruby but there must be also drawback's

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