Array.which_long? ( I coded an extension for Array )

ruby-talk
1

Hi, I'm CFC
I'm new at here.
Nice to meet you:)

I just coded an extension for Array.
It will return the longest element of an array.
Source:

class Array
  def which_long?
    # Version 1.0
    # Coded by CFC < zusocfc @ gmail . com >
    # PLEASE DO NOT REMOVE THE COMMENT OF THIS FUNCTION, THANKS A LOT.
    # Usage:
    # ['a', 'ab', 'abc' 1234].which_long?
    # => 1234
    max, long, self_cpy = 0, "", []
    self.size.times{|i| self_cpy << self[i].to_s}
    self_cpy.each{|item| (max = item.size; long = item) if item.size > max }
    long
  end
end

Usage:
  puts [1, 23, '456'].which_long?
  => 456

CFC --

2

How about:
class Array
  def longest
    self.map {|x| x.to_s }.sort_by {|x| x.size}[-1]
  end
end

···

On 4/29/07, Billy Hsu <ruby.maillist@gmail.com> wrote:

Hi, I'm CFC
I'm new at here.
Nice to meet you:)

> I just coded an extension for Array.

It will return the longest element of an array.
Source:

class Array
  def which_long?
    # Version 1.0
    # Coded by CFC < zusocfc @ gmail . com >
    # PLEASE DO NOT REMOVE THE COMMENT OF THIS FUNCTION, THANKS A LOT.
    # Usage:
    # ['a', 'ab', 'abc' 1234].which_long?
    # => 1234
    max, long, self_cpy = 0, "",
    self.size.times{|i| self_cpy << self[i].to_s}
    self_cpy.each{|item| (max = item.size; long = item) if item.size > max }
    long
  end
end

Usage:
  puts [1, 23, '456'].which_long?
  => 456

CFC --

--
Chris Carter
concentrationstudios.com
brynmawrcs.com

3

Hi --

Hi, I'm CFC
I'm new at here.
Nice to meet you:)

Welcome!

I just coded an extension for Array.
It will return the longest element of an array.
Source:

class Array
  def which_long?
    # Version 1.0
    # Coded by CFC < zusocfc @ gmail . com >
    # PLEASE DO NOT REMOVE THE COMMENT OF THIS FUNCTION, THANKS A LOT.
    # Usage:
    # ['a', 'ab', 'abc' 1234].which_long?
    # => 1234
    max, long, self_cpy = 0, "",
    self.size.times{|i| self_cpy << self[i].to_s}
    self_cpy.each{|item| (max = item.size; long = item) if item.size > max }
    long
  end
end

Usage:
  puts [1, 23, '456'].which_long?
  => 456

You're doing too much work -- let Ruby do it :slight_smile:

  class Array
    def longest
      map {|e| e.to_s }.max
    end
  end

David

···

On 4/29/07, Billy Hsu <ruby.maillist@gmail.com> wrote:

--
Upcoming Rails training by Ruby Power and Light:
  Four-day Intro to Intermediate
  May 8-11, 2007
  Edison, NJ
  http://www.rubypal.com/events/05082007

4

Hi,

Welcome.

You may be interested in this.
I did not study your code well but I think it is doing something similar.

p [1, 23, '456'].max {|x,y| x.to_s.size <=> y.to_s.size}

Harry

···

On 4/29/07, Billy Hsu <ruby.maillist@gmail.com> wrote:

Hi, I'm CFC
I'm new at here.
Nice to meet you:)

I just coded an extension for Array.
It will return the longest element of an array.
Source:

class Array
  def which_long?
    # Version 1.0
    # Coded by CFC < zusocfc @ gmail . com >
    # PLEASE DO NOT REMOVE THE COMMENT OF THIS FUNCTION, THANKS A LOT.
    # Usage:
    # ['a', 'ab', 'abc' 1234].which_long?
    # => 1234
    max, long, self_cpy = 0, "",
    self.size.times{|i| self_cpy << self[i].to_s}
    self_cpy.each{|item| (max = item.size; long = item) if item.size > max }
    long
  end
end

Usage:
  puts [1, 23, '456'].which_long?
  => 456

CFC --

--

A Look into Japanese Ruby List in English

5

Hi, I'm CFC
I'm new at here.
Nice to meet you:)

Likewise and welcome to the list :slight_smile:

I just coded an extension for Array.
It will return the longest element of an array.

I hope you posted this for comments, if not just ignore my post, you
will be in good company :wink:

Before I go into the details, one important point, ruby classes are
open which is one of the features of Ruby I like most, *but* be
careful with this, I use it a lot, but my rule is, never do this in a
library, or a program that might be designed for reuse, exceptions are
of course libraries which just do that, IOW libraries that are
designed and documented as an extensions of a core class.

Source:

class Array
  def which_long?
    # Version 1.0
    # Coded by CFC < zusocfc @ gmail . com >
    # PLEASE DO NOT REMOVE THE COMMENT OF THIS FUNCTION, THANKS A LOT.
    # Usage:
    # ['a', 'ab', 'abc' 1234].which_long?
    # => 1234
    max, long, self_cpy = 0, "",
    self.size.times{|i| self_cpy << self[i].to_s}
    self_cpy.each{|item| (max = item.size; long = item) if item.size > max }
    long
  end
end

def longest
  ... forget it skipping to David's reply

···

On 4/29/07, Billy Hsu <ruby.maillist@gmail.com> wrote:

Usage:
  puts [1, 23, '456'].which_long?
  => 456

CFC --

--
You see things; and you say Why?
But I dream things that never were; and I say Why not?
-- George Bernard Shaw

6

You're doing too much work -- let Ruby do it :slight_smile:

... for sure, but

  class Array
    def longest
      map {|e| e.to_s }.max
    end
  end

I think it is not exactly what OP wanted
because %w{x aaaa}.max is "x"
so I will try to comply to his needs
def longest
    map{ |e| [e.to_s.size, e.to_s]}.max.first
end

HTH
Robert

···

On 4/29/07, David A. Black <dblack@wobblini.net> wrote:

David

--
Upcoming Rails training by Ruby Power and Light:
  Four-day Intro to Intermediate
  May 8-11, 2007
  Edison, NJ
  http://www.rubypal.com/events/05082007

--
You see things; and you say Why?
But I dream things that never were; and I say Why not?
-- George Bernard Shaw

7

Thank you for leaving the #inject solutions to me. :slight_smile:

irb(main):001:0> %w{a ab abc 123 34}.inject{|a,b| a.size > b.size ? a : b}
=> "123"
irb(main):002:0> %w{a ab abc 123 34}.inject{|a,b| a.size >= b.size ? a : b}
=> "abc"

Kind regards

  robert

···

On 29.04.2007 16:11, Chris Carter wrote:

On 4/29/07, Billy Hsu <ruby.maillist@gmail.com> wrote:

Hi, I'm CFC
I'm new at here.
Nice to meet you:)

> I just coded an extension for Array.

It will return the longest element of an array.
Source:

class Array
  def which_long?
    # Version 1.0
    # Coded by CFC < zusocfc @ gmail . com >
    # PLEASE DO NOT REMOVE THE COMMENT OF THIS FUNCTION, THANKS A LOT.
    # Usage:
    # ['a', 'ab', 'abc' 1234].which_long?
    # => 1234
    max, long, self_cpy = 0, "",
    self.size.times{|i| self_cpy << self[i].to_s}
    self_cpy.each{|item| (max = item.size; long = item) if item.size > max }
    long
  end
end

Usage:
  puts [1, 23, '456'].which_long?
  => 456

CFC --

How about:
class Array
def longest
   self.map {|x| x.to_s }.sort_by {|x| x.size}[-1]
end
end

8

Hi --

> You're doing too much work -- let Ruby do it :slight_smile:
... for sure, but
>
> class Array
> def longest
> map {|e| e.to_s }.max
> end
> end
I think it is not exactly what OP wanted
because %w{x aaaa}.max is "x"
so I will try to comply to his needs
def longest
    map{ |e| [e.to_s.size, e.to_s]}.max.first
end

You're right that I was wrong (because I didn't do the .size thing),
but yours gives you an integer:

  ['x', 'aaaa'].longest # => 4

I think you'd have to reverse your array. See Harry's code too, which
uses a block with max. You could also do:

     sort_by {|e| e.to_s.size }[-1]

(since there's no max_by :slight_smile:

David

···

On 4/29/07, Robert Dober <robert.dober@gmail.com> wrote:

On 4/29/07, David A. Black <dblack@wobblini.net> wrote:

--
Upcoming Rails training by Ruby Power and Light:
  Four-day Intro to Intermediate
  May 8-11, 2007
  Edison, NJ
  http://www.rubypal.com/events/05082007

9

>> Hi, I'm CFC
>> I'm new at here.
>> Nice to meet you:)
>>
> > I just coded an extension for Array.
>> It will return the longest element of an array.
>> Source:
>>
>> class Array
>> def which_long?
>> # Version 1.0
>> # Coded by CFC < zusocfc @ gmail . com >
>> # PLEASE DO NOT REMOVE THE COMMENT OF THIS FUNCTION, THANKS A LOT.
>> # Usage:
>> # ['a', 'ab', 'abc' 1234].which_long?
>> # => 1234
>> max, long, self_cpy = 0, "",
>> self.size.times{|i| self_cpy << self[i].to_s}
>> self_cpy.each{|item| (max = item.size; long = item) if item.size >
>> max }
>> long
>> end
>> end
>>
>> Usage:
>> puts [1, 23, '456'].which_long?
>> => 456
>>
>> CFC --
>>
> How about:
> class Array
> def longest
> self.map {|x| x.to_s }.sort_by {|x| x.size}[-1]
> end
> end

Thank you for leaving the #inject solutions to me. :slight_smile:

Are you kidding I posted an inject solution 19h ago :wink:

But it was to return an array of all longest elements, I guess you can
maybe refine it, it seems clumsy, so I repost it just if you have some
time to play :wink:

def longest
          inject(){ |s, e|
                 if s.empty? || s.first.size < e.to_s.size then [e]
                 elsif s.first.size == e.to_s.size then s << e
                 else s
                 end
               }
end

irb(main):001:0> %w{a ab abc 123 34}.inject{|a,b| a.size > b.size ? a : b}
=> "123"
irb(main):002:0> %w{a ab abc 123 34}.inject{|a,b| a.size >= b.size ? a : b}

You get full credits for this anyway it is really beautiful, can you
stop being so clever ;).

Cheers
Robert

···

On 4/30/07, Robert Klemme <shortcutter@googlemail.com> wrote:

On 29.04.2007 16:11, Chris Carter wrote:
> On 4/29/07, Billy Hsu <ruby.maillist@gmail.com> wrote:

--
You see things; and you say Why?
But I dream things that never were; and I say Why not?
-- George Bernard Shaw

10

Thanks for your reply, I learned more on this thread :stuck_out_tongue:
But I have a question:
If I have an array contain:
  ary = [1, 12, 234, "456"]
there has two elements which size is 3, but the longest method just returned
one of them.
I can't solve it :frowning:

thank you, Chris, David, Harry and Robert :smiley:

CFC --

···

2007/4/29, David A. Black <dblack@wobblini.net>:

Hi --

On 4/29/07, Robert Dober <robert.dober@gmail.com> wrote:
> On 4/29/07, David A. Black <dblack@wobblini.net> wrote:
> > You're doing too much work -- let Ruby do it :slight_smile:
> ... for sure, but
> >
> > class Array
> > def longest
> > map {|e| e.to_s }.max
> > end
> > end
> I think it is not exactly what OP wanted
> because %w{x aaaa}.max is "x"
> so I will try to comply to his needs
> def longest
> map{ |e| [e.to_s.size, e.to_s]}.max.first
> end

You're right that I was wrong (because I didn't do the .size thing),
but yours gives you an integer:

['x', 'aaaa'].longest # => 4

I think you'd have to reverse your array. See Harry's code too, which
uses a block with max. You could also do:

    sort_by {|e| e.to_s.size }[-1]

(since there's no max_by :slight_smile:

David

--
Upcoming Rails training by Ruby Power and Light:
Four-day Intro to Intermediate
May 8-11, 2007
Edison, NJ
http://www.rubypal.com/events/05082007

--
Taiwan Ruby Users Group:
http://www.ruby.oss.tw/
http://www.ruby.oss.tw/phpbb

11

Hi --

> > You're doing too much work -- let Ruby do it :slight_smile:
> ... for sure, but
> >
> > class Array
> > def longest
> > map {|e| e.to_s }.max
> > end
> > end
> I think it is not exactly what OP wanted
> because %w{x aaaa}.max is "x"
> so I will try to comply to his needs
> def longest
> map{ |e| [e.to_s.size, e.to_s]}.max.first
> end

You're right that I was wrong (because I didn't do the .size thing),
but yours gives you an integer:

  ['x', 'aaaa'].longest # => 4

I think you'd have to reverse your array.

Together we might get there ;), maybe just applying #last instead of #first.
See Harry's code too, which

uses a block with max.

Which is great, I admit that is the nicest solution, learned something again :slight_smile:
You could also do:

     sort_by {|e| e.to_s.size }[-1]

That's nice too, (personally I prefer #last to [-1])

(since there's no max_by :slight_smile:

yet

Cheers
Robert

···

On 4/29/07, David A. Black <dblack@wobblini.net> wrote:

On 4/29/07, Robert Dober <robert.dober@gmail.com> wrote:
> On 4/29/07, David A. Black <dblack@wobblini.net> wrote:

--
You see things; and you say Why?
But I dream things that never were; and I say Why not?
-- George Bernard Shaw

12

Well, not yet:

$ ruby_yarv -e 'p %w[c bb aaa].max_by { |e| e.to_s.size }'
"aaa"

James Edward Gray II

···

On Apr 29, 2007, at 9:38 AM, David A. Black wrote:

Hi --

On 4/29/07, Robert Dober <robert.dober@gmail.com> wrote:

On 4/29/07, David A. Black <dblack@wobblini.net> wrote:
> You're doing too much work -- let Ruby do it :slight_smile:
... for sure, but
>
> class Array
> def longest
> map {|e| e.to_s }.max
> end
> end
I think it is not exactly what OP wanted
because %w{x aaaa}.max is "x"
so I will try to comply to his needs
def longest
    map{ |e| [e.to_s.size, e.to_s]}.max.first
end

You're right that I was wrong (because I didn't do the .size thing),
but yours gives you an integer:

['x', 'aaaa'].longest # => 4

I think you'd have to reverse your array. See Harry's code too, which
uses a block with max. You could also do:

    sort_by {|e| e.to_s.size }[-1]

(since there's no max_by :slight_smile:

13

>> Hi, I'm CFC
>> I'm new at here.
>> Nice to meet you:)
>>
> > I just coded an extension for Array.
>> It will return the longest element of an array.
>> Source:
>>
>> class Array
>> def which_long?
>> # Version 1.0
>> # Coded by CFC < zusocfc @ gmail . com >
>> # PLEASE DO NOT REMOVE THE COMMENT OF THIS FUNCTION, THANKS A LOT.
>> # Usage:
>> # ['a', 'ab', 'abc' 1234].which_long?
>> # => 1234
>> max, long, self_cpy = 0, "",
>> self.size.times{|i| self_cpy << self[i].to_s}
>> self_cpy.each{|item| (max = item.size; long = item) if item.size >
>> max }
>> long
>> end
>> end
>>
>> Usage:
>> puts [1, 23, '456'].which_long?
>> => 456
>>
>> CFC --
>>
> How about:
> class Array
> def longest
> self.map {|x| x.to_s }.sort_by {|x| x.size}[-1]
> end
> end

Thank you for leaving the #inject solutions to me. :slight_smile:

Are you kidding I posted an inject solution 19h ago :wink:

I am sorry, I did not see it.

But it was to return an array of all longest elements, I guess you can
maybe refine it, it seems clumsy, so I repost it just if you have some
time to play :wink:

def longest
         inject(){ |s, e|
                if s.empty? || s.first.size < e.to_s.size then [e]
                elsif s.first.size == e.to_s.size then s << e
                else s
                end
              }
end

Hm, I'd probably use case here. Let's see...

def longest
   inject() do |lg, e|
     case
       when lg.empty?, lg.first.size == e.size
         lg << e
       when lg.first.size < e.size
         [e]
       else
         lg
     end
   end
end

Alternative, but with higher memory consumption

def longest
   lg = Hash.new {|h,k| h[k] = }
   each {|x| lg[x.size] << x}
   lg.sort_by {|k,v| k}.last.pop
end

irb(main):001:0> %w{a ab abc 123 34}.inject{|a,b| a.size > b.size ? a : b}
=> "123"
irb(main):002:0> %w{a ab abc 123 34}.inject{|a,b| a.size >= b.size ? a : b}

You get full credits for this anyway it is really beautiful, can you
stop being so clever ;).

Since I overlooked your posting I can't be so clever, can I? :slight_smile:

With #inject it's really special, it took me a while to pick it up and now I can't stop using it. IIRC I even went to the exercise to implement all methods in Enumerable by using #inject - maybe you can find it in the archives. :slight_smile:

Kind regards

  robert

···

On 30.04.2007 12:39, Robert Dober wrote:

On 4/30/07, Robert Klemme <shortcutter@googlemail.com> wrote:

On 29.04.2007 16:11, Chris Carter wrote:
> On 4/29/07, Billy Hsu <ruby.maillist@gmail.com> wrote:

14

"Robert Dober" <robert.dober@gmail.com> writes:

But it was to return an array of all longest elements, I guess you can
maybe refine it, it seems clumsy, so I repost it just if you have some
time to play :wink:

def longest
         inject(){ |s, e|
                if s.empty? || s.first.size < e.to_s.size then [e]
                elsif s.first.size == e.to_s.size then s << e
                else s
                end
              }
end

That does seem clumsy. How about:

class Array
  def longest
    inject([0,]) { |(s,l),e|
      if e.to_s.size == s then [s,l << e]
      elsif e.to_s.size < s then [s,l]
      else [e.to_s.size, [e]]
      end
    }[1]
  end
end

Gotta love those destructuring block parameters.

···

--
s=%q( Daniel Martin -- martin@snowplow.org
       puts "s=%q(#{s})",s.to_a[1] )
       puts "s=%q(#{s})",s.to_a[1]

15

Hi --

Thanks for your reply, I learned more on this thread :stuck_out_tongue:
But I have a question:
If I have an array contain:
  ary = [1, 12, 234, "456"]
there has two elements which size is 3, but the longest method just returned
one of them.
I can't solve it :frowning:

It depends how you want to break the tie. Here's a way to do it where
a size tie is broken by string comparison, which is ASCII-based. The
nonzero? method will return -1 or 1 if the two string sizes are not
equal. If they are equal, the comparison will evaluate to zero and
nonzero? will be false -- which means the second comparison (the ASCII
one) will be executed.

I've included some tests too.

class Array
  def longest
    sort do |a,b|
      (a.to_s.size <=> b.to_s.size).nonzero? ||
      a.to_s <=> b.to_s
    end[-1]
  end
end

require 'test/unit'

class MaxTest < Test::Unit::TestCase

  def test_all_strings
    assert_equal("David", %w{ Da David Dav }.longest)
  end

  def test_all_numbers
    assert_equal(34567, [123,12345,200,34567].longest)
  end

  def test_tie
    assert_equal("David", %w{ David Alan Black }.longest)
  end

  def test_mixed
    assert_equal("David", [123, "David", 456].longest)
  end

  def test_mixed_tie
    assert_equal("David", [12345, "David", "Black", 123, 98765].longest)
  end
end

David

···

On 4/29/07, Billy Hsu <ruby.maillist@gmail.com> wrote:

2007/4/29, David A. Black <dblack@wobblini.net>:
>
> Hi --
>
> On 4/29/07, Robert Dober <robert.dober@gmail.com> wrote:
> > On 4/29/07, David A. Black <dblack@wobblini.net> wrote:
> > > You're doing too much work -- let Ruby do it :slight_smile:
> > ... for sure, but
> > >
> > > class Array
> > > def longest
> > > map {|e| e.to_s }.max
> > > end
> > > end
> > I think it is not exactly what OP wanted
> > because %w{x aaaa}.max is "x"
> > so I will try to comply to his needs
> > def longest
> > map{ |e| [e.to_s.size, e.to_s]}.max.first
> > end
>
> You're right that I was wrong (because I didn't do the .size thing),
> but yours gives you an integer:
>
> ['x', 'aaaa'].longest # => 4
>
> I think you'd have to reverse your array. See Harry's code too, which
> uses a block with max. You could also do:
>
> sort_by {|e| e.to_s.size }[-1]
>
> (since there's no max_by :slight_smile:
>
> David
>
> --
> Upcoming Rails training by Ruby Power and Light:
> Four-day Intro to Intermediate
> May 8-11, 2007
> Edison, NJ
> http://www.rubypal.com/events/05082007
>

--
Taiwan Ruby Users Group:
http://www.ruby.oss.tw/
http://www.ruby.oss.tw/phpbb

--
Upcoming Rails training by Ruby Power and Light:
  Four-day Intro to Intermediate
  May 8-11, 2007
  Edison, NJ
  http://www.rubypal.com/events/05082007

16

> (since there's no max_by :slight_smile:

Well, not yet:

when I said that above I just dreamt, I had no clue, conclusion =>
YARV fulfills your wildest dreams :wink:

$ ruby_yarv -e 'p %w[c bb aaa].max_by { |e| e.to_s.size }'
"aaa"

I guess there will be a #min_by too,
how does it break ties? Well I ask too much I gotta go the last snapshot...

BTW instead of
   a[ rand(a.size) ]
we can write
   a.max_by{ rand }
now; LOL!

Robert

···

On 4/29/07, James Edward Gray II <james@grayproductions.net> wrote:
--
You see things; and you say Why?
But I dream things that never were; and I say Why not?
-- George Bernard Shaw

17

Is this what you are looking for?
Do you want all longest elements?

big = [1, 12, 234,45,978, "456"].max {|x,y| x.to_s.size <=> y.to_s.size}
p [1, 12, 234,45,978, "456"].select {|r| r.to_s.size == big.to_s.size}

Harry

···

On 4/29/07, Billy Hsu <ruby.maillist@gmail.com> wrote:

Thanks for your reply, I learned more on this thread :stuck_out_tongue:
But I have a question:
If I have an array contain:
  ary = [1, 12, 234, "456"]
there has two elements which size is 3, but the longest method just returned
one of them.
I can't solve it :frowning:

--

A Look into Japanese Ruby List in English

18

I am sorry, I did not see it.

I was just kidding Robert.

> But it was to return an array of all longest elements, I guess you can
> maybe refine it, it seems clumsy, so I repost it just if you have some
> time to play :wink:
>
> def longest
> inject(){ |s, e|
> if s.empty? || s.first.size < e.to_s.size then [e]
> elsif s.first.size == e.to_s.size then s << e
> else s
> end
> }
> end

Hm, I'd probably use case here. Let's see...

def longest
   inject() do |lg, e|
     case
       when lg.empty?, lg.first.size == e.size
         lg << e
       when lg.first.size < e.size
         [e]
       else
         lg
     end
   end
end

better already, I am still looking for *the* solution

Alternative, but with higher memory consumption

def longest
   lg = Hash.new {|h,k| h[k] = }
   each {|x| lg[x.size] << x}
   lg.sort_by {|k,v| k}.last.pop
end

good idea but I wanted inject :slight_smile:

<snip>

Robert

···

On 4/30/07, Robert Klemme <shortcutter@googlemail.com> wrote:
--
You see things; and you say Why?
But I dream things that never were; and I say Why not?
-- George Bernard Shaw

19

def longest
    max = map{|s| s.size}.max
    select{|s| s.size == max}
end

···

On Apr 30, 6:47 am, Robert Klemme <shortcut...@googlemail.com> wrote:

On 30.04.2007 12:39, Robert Dober wrote:

> On 4/30/07, Robert Klemme <shortcut...@googlemail.com> wrote:
>> On 29.04.2007 16:11, Chris Carter wrote:
>> > On 4/29/07, Billy Hsu <ruby.maill...@gmail.com> wrote:
>> >> Hi, I'm CFC
>> >> I'm new at here.
>> >> Nice to meet you:)

>> > > I just coded an extension for Array.
>> >> It will return the longest element of an array.
>> >> Source:

>> >> class Array
>> >> def which_long?
>> >> # Version 1.0
>> >> # Coded by CFC < zusocfc @ gmail . com >
>> >> # PLEASE DO NOT REMOVE THE COMMENT OF THIS FUNCTION, THANKS A LOT.
>> >> # Usage:
>> >> # ['a', 'ab', 'abc' 1234].which_long?
>> >> # => 1234
>> >> max, long, self_cpy = 0, "",
>> >> self.size.times{|i| self_cpy << self[i].to_s}
>> >> self_cpy.each{|item| (max = item.size; long = item) if item.size >
>> >> max }
>> >> long
>> >> end
>> >> end

>> >> Usage:
>> >> puts [1, 23, '456'].which_long?
>> >> => 456

>> >> CFC --

>> > How about:
>> > class Array
>> > def longest
>> > self.map {|x| x.to_s }.sort_by {|x| x.size}[-1]
>> > end
>> > end

>> Thank you for leaving the #inject solutions to me. :slight_smile:
> Are you kidding I posted an inject solution 19h ago :wink:

I am sorry, I did not see it.

> But it was to return an array of all longest elements, I guess you can
> maybe refine it, it seems clumsy, so I repost it just if you have some
> time to play :wink:

> def longest
> inject(){ |s, e|
> if s.empty? || s.first.size < e.to_s.size then [e]
> elsif s.first.size == e.to_s.size then s << e
> else s
> end
> }
> end

Hm, I'd probably use case here. Let's see...

def longest
   inject() do |lg, e|
     case
       when lg.empty?, lg.first.size == e.size
         lg << e
       when lg.first.size < e.size
         [e]
       else
         lg
     end
   end
end

Alternative, but with higher memory consumption

def longest
   lg = Hash.new {|h,k| h[k] = }
   each {|x| lg[x.size] << x}
   lg.sort_by {|k,v| k}.last.pop
end

20

Actually Array#max already takes a block, and the Rdoc actually uses
almost this very use case to document it:

$ qri Array#max
--------------------------------------------------------- Enumerable#max
     enum.max => obj
     enum.max {|a,b| block } => obj

···

On 4/29/07, James Edward Gray II <james@grayproductions.net> wrote:

On Apr 29, 2007, at 9:38 AM, David A. Black wrote:

> I think you'd have to reverse your array. See Harry's code too, which
> uses a block with max. You could also do:
>
> sort_by {|e| e.to_s.size }[-1]
>
> (since there's no max_by :slight_smile:

Well, not yet:

$ ruby_yarv -e 'p %w[c bb aaa].max_by { |e| e.to_s.size }'
"aaa"

------------------------------------------------------------------------
     Returns the object in enum with the maximum value. The first form
     assumes all objects implement Comparable; the second uses the
     block to return a <=> b.

        a = %w(albatross dog horse)
        a.max #=> "horse"
        a.max {|a,b| a.length <=> b.length } #=> "albatross"

Harry gave a solution along these lines early on in the thread, but no
one seems to have noticed.

The observation that 1.9 is adding max_by is interesting, but it's
more a matter of syntactic sugar than the difference between sort and
sort_by since max only needs to evaluate the block once for each
element.

Now max_by is nicer since the block just needs to return the
comparison value rather than a comparison result.

--
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/