From: "Benjamin J. Tilly" <ben_tilly@...>
Date: 2001-06-19T03:44:19+09:00
Subject: [ruby-talk:16599] RE:  RCR: Enumerable: every() and none()

>===== Original Message From Hugh Sasse Staff Elec Eng <hgs@dmu.ac.uk> =====
>I've been off the list for a while but I'm dipping back in to suggest:
>
>Enumerable should have functions every and none to complement find_all
>and reject.  I think it is likely that people will want to know if all
>the things in the enumObj match or all don't match the conditions
>specified by block. So:

Personally I would use detect (or equivalently find) with a not
inserted either before the detect (for none) or before the
condition in the block (for every).  I am comfortable putting
that logic inline, and when possible I like having a relatively
small circle of ideas that play well together rather than a lot
of slightly different permutations on the same thing.

YMMV.

It will definitely vary if your array potentially contains nil
or false and you are interested in detecting that.  The
overloading of the return of detect/find makes this problematic,
however the situation does not appear to arise as often as you
might fear.  (However it is something to be aware of.)

>def every(&block)
>    find_all(&block) == to_a()
>end
>
>def none(&block)
>    reject(&block) == to_a()
>end

[...]
>that EVERY *params is numeric, or that EVERY *params is a trapezoid....
>I submit that this is generalized enough and useful enough to merit
>inclusion in ruby, hence my proposing this RCR.  There may be a more 
efficient
>way to implement this than with the above code, so that is intended only
>as a description of functionality.

I would definitely recommend breaking out on the first element
found that didn't fit the assertion.  Failing, that the following
will be more efficient, particularly if the collection has
complex entries:

  def every(&block)
    reject(&block) == []
  end

  def none(&block)
    find_all(&block) == []
  end


Cheers,
Ben