From: David Masover <ninja@...>
Date: 2009-09-15T10:15:51+09:00
Subject: Re: [1,2,3].map.with_object(3){|v|v+3} #=> 3 Is this a bug?

On Sunday 13 September 2009 09:19:31 pm ErMaker wrote:
> At ruby 1.9.2dev (2009-07-18 trunk 24186) [i386-mswin32_90]
>
> Ruby runs like this.
>
> >> [1,2,3].map.with_object(3){|v|v+3}
>
> => 3
>
> >> [1,2,3].each.with_object(3).map{|v|v+3}
>
> => [4, 5, 6]

That makes sense, now that I know what with_object does.

> I think that is better to use.
>
> >> [1,2,3].map.with_object(3){|v|v+3}
>
> => [4, 5, 6]
>
> Is it a bug?

I doubt it -- map is the only iterator that returns the results of each 
iteration.

In fact, if you look at what with_object does, it's doing exactly what it's 
designed to:

irb(main):041:0> [1,2,3].each.with_object({}){|x,h| h[x] = x**2}
=> {1=>1, 2=>4, 3=>9}

I don't see why you want to do with_object at all -- your above example would 
work just fine as:

[1,2,3].map{|v|v+3}

If you wanted to use a variable, you could do that too:

x = 3
[1,2,3].map{|v|v+x}

I can't imagine why you'd want to have the behavior of foo.with_object.map, 
ever. Could you please give more context?