From: Anders Borch <spam@...>
Date: 2003-05-31T03:13:16+09:00
Subject: Re: Iteration - last detection

John Johnson wrote:
> 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
> }

that would only work if the array is sorted...


> 
> 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
>>>
>>
>>
> 
> 


-- 
dc -e 4dd*od3*ddn1-0nn1dnd+nn3dn1+n3*1+ddn1+dn2-n5dn1+dnrn1-p | tr 
0123456 yorh@k. | dd conv=lcase