From: Robert Klemme <bob.news@...>
Date: 2006-01-08T07:43:00+09:00
Subject: Re: Iterator Fu Failing Me

Bob Hutchison <hutch@recursive.ca> wrote:
> On Jan 7, 2006, at 1:08 PM, Robert Klemme wrote:
>>>
>>> You mean #detect or #select?
>>
>> #detect - because it stops as soon as it has a hit while #select
>> will return an array.  We need just the first hit.
>>
>>>> [nil,nil,nil,"w",2,3].find {|x|puts x;x}
>> nil
>> nil
>> nil
>> w
>> => "w"
>>>> [nil,nil,nil,"w",2,3].select {|x|puts x;x}
>> nil
>> nil
>> nil
>> w
>> 2
>> 3
>> => ["w", 2, 3]
>>
>
> The trouble is that detect returns the 'x' not the result of
> processing x successfully (or, in terms of the original post, the
> class that accepts the token not the result of the #parse? method).
> That's why you have to capture the result in the block. Map returns
> the result of processing.

Aargh!  I shoul've tested more carefully.  Yes you're completely right.  But 
the inject version still works, I think that's then my favourite.

elements = tokens.map do |tok|
  parsers.inject(false) {|a,pars| a = pars.parse? tok and break a}
end

Thanks for correcting me!

    robert