From: Robert Klemme <shortcutter@...>
Date: 2007-05-27T20:35:02+09:00
Subject: Re: Introducing the "it" keyword

On 27.05.2007 11:46, Robert Dober wrote:
> On 5/27/07, Robert Klemme <shortcutter@googlemail.com> wrote:
> <snip>
>> >>
>> > That is something I am surprised about, b/c the intention was to have
>> > an idiom for
>> > return it if h(x) < 10
>>
>> No, it's "return it if it < 10" with "it" being "v+1" in this case.
> Well that was the original idiom but we are looking for existing ones, 
> right?

Yes, and that's why I presented what I presented.  I am not sure I 
understand your point here. :-)

>> > and
>> > return it_test(h(x))
>> > really is not the same, right?
>>
>> It's not the same but I believe you misread the task.  it_test is just a
>> method to demonstrate the idiom in lines 2-4.
> 
> Ah that's why you called the method test_..., not stupid at all ;)
> Well I will get to understand what is going on here...
> .. eventually...
> .. potentially...
> .. maybe...
> .. hardly...

Um...  It's really not that difficult.  I just used instance_eval 
because that will rebind "self" inside the block but retain the original 
binding afterwards.  That way you get something like a "temporary 
variable" but without needing to manually make sure the reference is 
released after the test.  Remeber that the problem with my first 
suggestion was that you had to add tmp=nil after the line with return in 
order to make sure the object would be released again.

It is really just the built in way of doing what is known in other 
languages as "with":

irb(main):001:0> def with(x,&b) x.instance_eval(&b) end
=> nil
irb(main):002:0> with "" do
irb(main):003:1*   p length
irb(main):004:1>   p empty?
irb(main):005:1> end
0
true
=> nil
irb(main):009:0> with "aaaaaaaaa" do
irb(main):010:1*   scan(/a{1,3}/) {|x| p x}
irb(main):011:1> end
"aaa"
"aaa"
"aaa"
=> "aaaaaaaaa"
irb(main):012:0>

Hope that explains it.   If not, let me know.

Kind regards

	robert