From: nobu.nokada@...
Date: 2002-11-27T20:30:31+09:00
Subject: Re: set operation

Hi,

At Wed, 27 Nov 2002 20:18:15 +0900,
Tim Bates wrote:
> > if ([string] & array_of_strings).length!=0 then....
> 
> I don't know what 'in' is used for, but another way to do this might be
> if [array_of_strings].index(myString) then...

Or:

  array_of_strings.include?(myString)

If array_of_strings is large and invariant, you may want to
prepare a hash whose keys are the elements.

  hash_of_srings = {}
  array_of_strings.each {|s| hash_of_srings[s] = true}
  ...
  if hash_of_srings[myString]

Array#index and Array#include? are O(n) order but Hash#[] is
O(1).

-- 
Nobu Nakada