From: Hank Gong <hankgong@...>
Date: 2005-12-13T04:25:28+09:00
Subject: Re: A question about recursive programming

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You program works.
Mine one listed here:

 def max(arr)
    case arr.size
        when 1 then return arr.first   ＃<---Wrong
        when arr.first>max(arr[1..-1]) then return arr.first
        else return max(arr[1..-1])
    end
end

c=[1,2,3,5,10,3,5,2]
p max(c)

Because the line with wrong comments make error when the max function
recurse to the deepest level, my function only print the last elements of
array.

On 12/13/05, mental@rydia.net <mental@rydia.net> wrote:
>
> Quoting Hank Gong <hankgong@gmail.com>:
>
> > And also I think it's not easy to think every loop as recursive
> > way.
>
> > For example it's very difficult to write max function by
> > recursive function.
>
> iterative:
>
> def max( *values )
>   case values.size
>   when 0
>     nil
>   when 1
>     values[0]
>   else
>     i = 1
>     max = values[0]
>     while i < values.size
>       max = values[i] if values[i] > max
>       i = i + 1
>     end
>     max
>   end
> end
>
> recursive:
>
> def max( *values )
>   case values.size
>   when 0
>     nil
>   when 1
>     values[0]
>   else
>     max_helper( values, 1, values[0] )
>   end
> end
>
> def max_helper( values, i, max )
>   if i < values.size
>     max = values[i] if values[i] > max
>     max_helper( values, i + 1, max )
>   else
>     max
>   end
> end
>
> -mental
>
>

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