From: Robert Klemme <shortcutter@...>
Date: 2011-05-11T06:25:29+09:00
Subject: Re: Enumerable#find returns an enumerator?

On 10.05.2011 22:33, Lars Schirrmeister wrote:
> The find method on an array takes a block and returns an enumerator
> if no block is given. The value you pass to the find method is not
> the value you want to find but the value which is returned if no
> block evaluates to true.

More precisely: the value passed is something which returns the 
replacement value when #called:

irb(main):007:0> (10..20).to_a.find(99) {|x| x > 150}
NoMethodError: undefined method `call' for 99:Fixnum
         from (irb):7:in `find'
         from (irb):7
         from /usr/local/bin/irb19:12:in `<main>'
irb(main):008:0> (10..20).to_a.find(lambda {99}) {|x| x > 150}
=> 99

Which is precisely what the docs say:

$ ri19 -T Enumerable#find
-------------------------------------------------------- Enumerable#find
      enum.detect(ifnone = nil) {| obj | block }  => obj or nil
      enum.find(ifnone = nil)   {| obj | block }  => obj or nil

      From Ruby 1.9.1
------------------------------------------------------------------------
      Passes each entry in _enum_ to _block_. Returns the first for which
      _block_ is not +false+. If no object matches, calls _ifnone_ and
      returns its result when it is specified, or returns +nil+

         (1..10).detect  {|i| i % 5 == 0 and i % 7 == 0 }   #=> nil
         (1..100).detect {|i| i % 5 == 0 and i % 7 == 0 }   #=> 35

There are places where Ruby's documentation is bad but here 
documentation is clear.  Why do so many people tell different stories if 
it is so easy to read this up in documentation?  (And, btw, it has been 
that way in all versions from 1.8.6 on.)

Cheers

	robert


-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/