From: Robert Klemme <shortcutter@...>
Date: 2009-12-11T18:14:40+09:00
Subject: Re: human-readable listing of array elements

2009/12/11 w_a_x_man <w_a_x_man@yahoo.com>:
> On Dec 10, 8:36 am, Robert Klemme <shortcut...@googlemail.com> wrote:
>> 2009/12/10 Aldric Giacomoni <ald...@trevoke.net>:
>>
>> > This took me less than a minute to write, but I don't know if it's as
>> > elegant as it could be. Are there more "Ruby-like ways(tm)" to write
>> > this?
>>
>> > def stringify array
>> >  return array[0] if array.size == 1
>> >  string = ""
>> >  array.each_with_index do |element, index|
>> >    case index
>> >      when array.size - 1 # last item
>> >        string += " and #{element}"
>> >      when 0
>> >        string += "#{element}"
>> >      else
>> >        string += ", #{element}"
>> >    end
>> >  end
>> >  string
>> > end
>>
>> By using String#<< your code will become more efficient because you do
>> not create new String objects all the time.
>>
>> For the fun of it here are two other solutions:
>>
>> irb(main):026:0> def stringify array
>> irb(main):027:1>   lead = array.slice 0...-1
>> irb(main):028:1>   lead.empty? ? array.last.to_s : [lead.join(", "),
>> array.last].join(" and ")
>> irb(main):029:1> end
>> => nil
>> irb(main):031:0> stringify []
>> => ""
>> irb(main):032:0> stringify %w{foo}
>> => "foo"
>> irb(main):033:0> stringify %w{foo bar}
>> => "foo and bar"
>> irb(main):034:0> stringify %w{foo bar baz}
>> => "foo, bar and baz"
>>
>> irb(main):039:0> def stringify array
>> irb(main):040:1>   tail = array.slice -2..-1
>> irb(main):041:1>   tail ? (array.slice(0...-2) << tail.join(" and
>> ")).join(", ") : array.first.to_s
>> irb(main):042:1> end
>>
>> irb(main):048:0> stringify []
>> => ""
>> irb(main):045:0> stringify %w{foo}
>> => "foo"
>> irb(main):046:0> stringify %w{foo bar}
>> => "foo and bar"
>> irb(main):047:0> stringify %w{foo bar baz}
>> => "foo, bar and baz"
>>
>> Note, I don't claim that this is necessarily more rubyish. :-)
>>
>> Kind regards
>>
>> robert
>>
>> --
>> remember.guy do |as, often| as.you_can - without endhttp://blog.rubybestpractices.com/
>
> Sometimes it's fun to avoid using conditionals (including
> "... ? ... : ...")
> when programming.

Here's one way that completely gets rid of case and if. :-)

ALG = Hash.new( lambda {|a| [a[0...-1].join(", "), a[-1]].join(" and
")} ).merge(
  0 => lambda {|a| ""},
  1 => lambda {|a| a.first.to_s},
  2 => lambda {|a| a.join " and "}
)

def s(a)
  ALG[a.size][a]
end

arr = []

5.times do |i|
  p arr, s(arr)
  arr << "foo#{i}"
end

> def to_string ary
>  a = ary.dup
>  a.push( a.pop(2).join " and " ).join ", "
> end

Nice!

Cheers

robert


-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/