From: tjnogueira@...
Date: 2008-12-26T20:21:48+09:00
Subject: Re: Buiding anamgrams

That's it. In ruby 1.8.6 you cant use this form , only for 1.8.7 and prior
...
I tested here and the code works perfectly.
About your class:
class Anagrams
>>   attr :word
>>   include Enumerable
>>   include Comparable
>>
>>   def <=>(other)
>>     self.word <=> other.word
>>   end
>>
>>   def each(&block)
>>     @word.chars
>>   end
>>
>>   def initialize(word)
>>     @word = word
>>   end
>>
>> end
i really dont understant what it means. Explain better.
King regards
tiago




On Fri, 26 Dec 2008 19:50:00 +0900, Robert Klemme
<shortcutter@googlemail.com> wrote:
> On 26.12.2008 10:30, andrea wrote:
>> I'm studying ruby (and I really love it even more than python) and I
>> want to do a little exercise.
> 
> Welcome to the pack!  What a nice Christmas occupation. :-)
> 
>> I want to create an efficient module to generate every possible
>> anagrams of a word, of any given size...
> 
> Do you really mean "anagrams" or rather "permutations"?  To decide on
> anagrams you likely need some kind of dictionary which is significantly
> more difficult than just permuting.
> 
>> I already done this in python, I want to see how can it be elegant in
>> ruby...
>> I need a good permutation algorithm (this
>>
> http://www.cut-the-knot.org/Curriculum/Combinatorics/JohnsonTrotter.shtml
>> works fine) and I'd like to use enumerators in the best and most
>> efficient way.
> 
>  From 1.8.7 on you can do this
> 
> irb(main):009:0> "abc".scan(/./).permutation {|x| p x.join}
> "abc"
> "acb"
> "bac"
> "bca"
> "cab"
> "cba"
> => ["a", "b", "c"]
> irb(main):010:0> "abc".chars.to_a.permutation {|x| p x.join}
> "abc"
> "acb"
> "bac"
> "bca"
> "cab"
> "cba"
> => ["a", "b", "c"]
> irb(main):011:0>
> 
> Now you only need a filter that properly decides which of those is a
> proper word and use that to decide which words to print and which not.
> 
>> I also looked at callcc which is great for backtracking, could be used
>> in this case??
> 
> I would try to avoid it as it makes code very hard to read - at least
> for me. :-)
> 
>> thanks for any help
>>
>> A basic structure like that could be fine?
>> class Anagrams
>>   attr :word
>>   include Enumerable
>>   include Comparable
>>
>>   def <=>(other)
>>     self.word <=> other.word
>>   end
>>
>>   def each(&block)
>>     @word.chars
>>   end
>>
>>   def initialize(word)
>>     @word = word
>>   end
>>
>> end
> 
> What exactly should be the responsibility of this class?  Especially,
> why do you call it "anagrams" but store only one word in it?
> 
> Cheers
> 
> 	robert
> 
> --
> remember.guy do |as, often| as.you_can - without end