From: botp <botpena@...>
Date: 2010-09-20T14:34:41+09:00
Subject: Re: how to get Mycompute.sum([1,2,3,4]).mean=2.5?

On Mon, Sep 20, 2010 at 11:47 AM, Pen Ttt <myocean135@yahoo.cn> wrote:
> class  Mycompute
>  def  self.sum(a)
>    a.inject(0){|s,i|s+i}
>  end
>  def  self.mean(a)
>    a.inject(0){|s,i|s+i}/(a.size.to_f)
>  end
> end
> Mycompute.sum([1,2,3,4])
> => 10
> Mycompute.mean([1,2,3,4])
> => 2.5
>
> how  can i  get  Mycompute.sum([1,2,3,4]).mean=2.5?

uh,uh, you cant because you get a conflict: your sum returns a value
(not array), and your mean is chaining on sum's return value, but mean
in turn requires its values coming fr its arguments.... in short:
confusing...

my suggestion is, start simple as possible,  eg

$ irb
>> class  Mycompute
>>   def initialize(arr)
>>     @arr=arr
>>   end
>>
?>   def values
>>     @arr
>>   end
>>
?>   def size
>>     @arr.size
>>   end
>>
?>   def sum
>>     @arr.inject(0.0){|s,i|s+i}
>>   end
>>
?>   def mean
>>     sum/size
>>   end
>> end
=> nil
>>
?> x = Mycompute.new([1,2,3,4])
=> #<Mycompute:0x0000000102cca8 @arr=[1, 2, 3, 4]>
>> p x.sum
10.0
=> 10.0
>> p x.mean
2.5
=> 2.5
>> p x.values
[1, 2, 3, 4]
=> [1, 2, 3, 4]
>> p x.values.min
1
=> 1
>> p x.values.count
4
=> 4
>> p x.values.map{|x| x*x}
[1, 4, 9, 16]
=> [1, 4, 9, 16]

kind regards -botp