How to sort this array


#1

Hi,

I have an array containing files names. How do I sort them so that I can
get the expected results?

Thanks,

Li

#############
files=[
“c:/ruby/self/2004/20.txt”,
“c:/ruby/self/2004/3.txt”,
“c:/ruby/self/2004/2.txt”,
“c:/ruby/self/2004/10.txt”,
“c:/ruby/self/2004/1.txt”
]

expected results:
[
“c:/ruby/self/2004/1.txt”,
“c:/ruby/self/2004/2.txt”,
“c:/ruby/self/2004/3.txt”,
“c:/ruby/self/2004/10.txt”,
]
“c:/ruby/self/2004/20.txt”,


#2

Li Chen wrote:

Hi,

I have an array containing files names. How do I sort them so that I can
get the expected results?

Thanks,

Li

#############
files=[
“c:/ruby/self/2004/20.txt”,
“c:/ruby/self/2004/3.txt”,
“c:/ruby/self/2004/2.txt”,
“c:/ruby/self/2004/10.txt”,
“c:/ruby/self/2004/1.txt”
]

expected results:
[
“c:/ruby/self/2004/1.txt”,
“c:/ruby/self/2004/2.txt”,
“c:/ruby/self/2004/3.txt”,
“c:/ruby/self/2004/10.txt”,
]
“c:/ruby/self/2004/20.txt”,

You get that result because in “2” <=> “10” the comparison is byte by
byte and then “2” is > “1”, so it aborts there with “2” being > than
“10”.
What you want is called natural sorting. Googling for natsort and ruby
you should get a few results.

Regards
Stefan


#3

here is my code:

C:\Users\Alex>irb
irb(main):001:0> files=[
irb(main):002:1* “c:/ruby/self/2004/20.txt”,
irb(main):003:1* “c:/ruby/self/2004/3.txt”,
irb(main):004:1* “c:/ruby/self/2004/2.txt”,
irb(main):005:1* “c:/ruby/self/2004/10.txt”,
irb(main):006:1* “c:/ruby/self/2004/1.txt”
irb(main):007:1> ]
=> [“c:/ruby/self/2004/20.txt”, “c:/ruby/self/2004/3.txt”,
“c:/ruby/self/2004/2.txt”, “c:/ruby/self/
2004/10.txt”, “c:/ruby/self/2004/1.txt”]
irb(main):008:0>
irb(main):009:0*
irb(main):010:0* files=files.sort_by do|s|
irb(main):011:1* s.split(///)[-1].split(/./)[0].to_i
irb(main):012:1> end
=> [“c:/ruby/self/2004/1.txt”, “c:/ruby/self/2004/2.txt”,
“c:/ruby/self/2004/3.txt”, “c:/ruby/self/2
004/10.txt”, “c:/ruby/self/2004/20.txt”]
irb(main):013:0>

I am not sure if it is the Rubyish way.

Li


#4

On Fri, Oct 31, 2008 at 06:14:51AM +0900, Li Chen wrote:

files=[
“c:/ruby/self/2004/2.txt”,
“c:/ruby/self/2004/3.txt”,
“c:/ruby/self/2004/10.txt”,
]
“c:/ruby/self/2004/20.txt”,

files = files.sort_by { |f| f[//(\d+).[^/]*\Z/, 1].to_i }

There are several things to explain here:

  • The #sort_by method calls the block on each element to produce a set
    of
    surrogate values to use as sorting keys.

  • The regular expression captures the series of digits between the last
    slash in a string and the following dot.

  • The [] method can be called on String in many ways, including passing
    a
    RegExp and an index. That form returns the capture of the appropriate
    index from matching the RegExp or nil if the RegExp does not match.

  • Calling #to_i on the result means that it will either parse the
    captured
    sequence of digits as an integer or, if the RegExp fails, return 0.

–Greg


#5

“c:/ruby/self/2004/1.txt”,
“c:/ruby/self/2004/2.txt”,
“c:/ruby/self/2004/3.txt”,
“c:/ruby/self/2004/10.txt”,
“c:/ruby/self/2004/20.txt”,
]

files.sort_by { | fn | fn.match(/(\d+).txt$/)[1].to_i }

mfg, simon … hth


#6

On Fri, Oct 31, 2008 at 5:14 AM, Li Chen removed_email_address@domain.invalid wrote:

expected results:
[ “c:/ruby/self/2004/1.txt”,
“c:/ruby/self/2004/2.txt”,
“c:/ruby/self/2004/3.txt”,
“c:/ruby/self/2004/10.txt”,
“c:/ruby/self/2004/20.txt”,
]

apology in advance for dupl email. i sent an email an hrs back but it
seems it got blackholed :slight_smile:

anyway, if you want basename numeric sorting, then just do

eg,

files.sort_by{|f| File.basename(f).to_i}


#7

2008/10/31 botp removed_email_address@domain.invalid:

seems it got blackholed :slight_smile:

anyway, if you want basename numeric sorting, then just do

eg,

files.sort_by{|f| File.basename(f).to_i}

Very elegant! Here’s another variant

irb(main):013:0> puts files.sort_by {|f| f[/\d+(?=.txt$)/].to_i}
c:/ruby/self/2004/1.txt
c:/ruby/self/2004/2.txt
c:/ruby/self/2004/3.txt
c:/ruby/self/2004/10.txt
c:/ruby/self/2004/20.txt
=> nil

Kind regards

robert


#8

And here’s a variant for cases where there are multiple subdirectories:

irb(main):010:0> puts files.sort_by {|f| f.scan(/\d+/).map{|x|x.to_i}}
c:/ruby/self/2004/1.txt
c:/ruby/self/2004/2.txt
c:/ruby/self/2004/3.txt
c:/ruby/self/2004/10.txt
c:/ruby/self/2004/20.txt

Kind regards

robert


#9

On Oct 30, 2008, at 6:34 PM, Simon K. wrote:

expected results:
mfg, simon … hth
Since #to_i will stop at a non-digit, you could get simpler:

files.sort_by {|fn| fn[%r{.*/([^/]+)},1].to_i }

I tend to use %r{ } when the Regexp deals with / characters.

-Rob

Rob B. http://agileconsultingllc.com
removed_email_address@domain.invalid