= SixArm Ruby Gem: email address validation using RFC 822 pattern matching

Author:: Joel Parker Henderson, joelparkerhenderson@gmail.com
Copyright:: Copyright (c) 2006-2010 Joel Parker Henderson
License:: CreativeCommons License, Non-commercial Share Alike
License:: LGPL, GNU Lesser General Public License

Email address regex, to validate an email address using RFC 822.

This is a gem wrapper around http://tfletcher.com/lib/rfc822.rb

Example:
  if EMAIL_ADDRESS_PATTERN=~'foo@bar.com'
    puts "found" 
  else
    puts "not found"
  end
  => found

To find an email address in a string, do the pattern match
then use the result, which is the match's string position:

Example of match position:
  match_position = EMAIL_ADDRESS_PATTERN=~'foo@bar.com'
  => 0

  match_position = EMAIL_ADDRESS_PATTERN=~'... foo@bar.com ...'
  => 4

  match_position = EMAIL_ADDRESS_PATTERN=~'... hello world ...'
  => nil

To do an exact pattern match, use the EMAIL_ADDRESS_EXACT_PATTERN.
This matches the entire string from start to end; in other words,
the entire string must be one email address.

Example of exact pattern match:
  if EMAIL_ADDRESS_EXACT_PATTERN=~'foo@bar.com' 
    puts "found" 
  else
    puts "not found"
  end
  => found

  if EMAIL_ADDRESS_EXACT_PATTERN=~'... foo@bar.com ...' 
    puts "found" 
  else
    puts "not found"
  end
  => not found

The exact pattern is especialy useful to validate an email address.

Example to validate an email address:
  def valid?(email_address)
    EMAIL_ADDRESS_EXACT_PATTERN=~email_address ? true : false
  end