From: John Johnson <jj5412@...>
Date: 2003-05-30T21:22:10+09:00
Subject: Re: Iteration - last detection

I may be over simplifiying, but Enumerable defines max, so couldn't you:

a = {}
a["a"] = "A"
a["b"] = "B"
a["c"] = "C"
a.each { |key, val|
  print "#{key} = #{val}"
  if key === a.keys.max
    puts " and that's the last one"
  else
    puts
  end
}

Regards,
  JJ

on 5/30/03 8:08 AM, Robert at bob.news@gmx.net wrote:

> Detecting if the first element might in some circumstances server the same
> purpose and it's easy done without Thread tricks:
> 
> def print_format(enum)
> first = true
> str = "["
> 
> enum.each do |e|
> if first
> first = false
> else
> str << ", "
> end
> 
> str << e.to_s
> end
> 
> str << "]"
> str
> end
> 
> 
> a=[10, 30, "foo"]
> puts print_format(a)
> 
> robert
> 
> 
> "Carlos" <angus@quovadis.com.ar> schrieb im Newsbeitrag
> news:20030530113250.GB1403@quovadis.com.ar...
>>> Is there any built in functionality for iteration that will allow me to
>>> detect when I am on the last element?  This would not be hard for an
> Array,
>>> using array.length, but what about a Hash?  How would I know when I am
> at
>>> the last element?
>> 
>> Here is a module that implements it, but you should include it in every
>> class where you want #each to behave that way :-/. (And some #each-like
>> methods (for example, String#each_byte, don't work at all...)
>> 
>> oe.rb:
>> #!/usr/bin/ruby
>> 
>> class Object
>> def last?
>> Thread.current.last_iteration?
>> end
>> private :last?
>> end
>> 
>> class Thread
>> def last_iteration?
>> @__last_iteration__
>> end
>> end
>> 
>> module EachWithLast
>> def EachWithLast.append_features(klass)
>> old_each="each_"+rand(10000).to_s+Time.now.usec.to_s
>> klass.class_eval <<-FINISH
>> alias_method :#{old_each}, :each
>> 
>> def each(*a,&b)
>> element = nil
>> flag = false
>> #{old_each}(*a) { |e|
>> Thread.current.instance_eval {
>> @__last_iteration__=false
>> }
>> b.call element if flag
>> flag=true
>> element=e
>> }
>> if flag
>> Thread.current.instance_eval {
>> @__last_iteration__=true
>> }
>> b.call element
>> Thread.current.instance_eval {
>> @__last_iteration__=false
>> }
>> end
>> end
>> FINISH
>> end
>> end
>> 
>> class Array; include EachWithLast end
>> 
>> a = [1,2,3,4,5].select {|e| last? }
>> p a  # => [5]
>> 
>> class Range; include EachWithLast end
>> class String; include EachWithLast end
>> 
>> for i in 1..10
>> print "and the last is: " if last?
>> print i
>> "ds\njkd\njsk\nsd".each { |l| puts " - the last line is #{l}" if last? }
>> end
>> 
>> class File; include EachWithLast end
>> File.open("oe.rb") { |f|
>> count = 0
>> f.each { |line|
>> count += line.length
>> print "last line: #{line}" if last?
>> }
>> print "total chars: #{count}\n"
>> }
>> #THE LAST LINE
>> 
> 
>