From: gotoken@... (GOTO Kentaro)
Date: 2000-02-15T22:34:45+09:00
Subject: [ruby-talk:01382] Re: nice sample for functional stuff

Hi,

In message "[ruby-talk:01378] Re: nice sample for functional stuff"
    on 00/02/15, Pixel <pixel_@mandrakesoft.com> writes:
>> >       def sum
>> >         inject(0) {|n, i| n += i }
>                                ^^ why ??
>
>        inject(0) {|n, i| n + i }
>
>seems enough to me, uh?

Yes. You are right. 

>uh? your solution gives ([].sum == nil), tis still not the best. mine has the
>same problem
>
>l = [1]
>l.sum + 1 #=> 2
>
>l.shift
>l.sum + 1 #=> Exception
>
>-> [].sum should raise an exception

Well, I didn't expect that the vaule of sum is a numeric then.  If I
would expect a integer, I specifies explicitly:

  l.sum.to_i + 1

This is very clear for me. But the following may be liked:

  def sum(value_for_empty = 0)
    inject(value_for_empty){|n,i| n+i}
  end

  [].sum + 1          #=> 1
  [].sum(0) + 1       #=> 1
  [].sum([]) + "tail" #=> ["tail"]
  [].sum("") + "tail" #=> "tail"

I can't choose better one though.  All I can say is I rather *like*
explicit conversion style.

>(perl has no such problem as "" is 0 is undef is ... :)

I believe I understand what you say, but sometimes such an implicit
conversion makes a bug which is not easy to find (at least for me).
It is one of favorite points, that is, Ruby's variable is type free
but Ruby does not do type conversion unless a user specify that.

Thanks,

-- gotoken