Various types of Ruby string equality comparisons

string equivalency in ruby

>> s1 = "a"
=> "a"
>> s2 = "a"
=> "a"
>> s3 = s1
=> "a"

>> puts "s1 & s2 #{s1 == s2 ? 'do' : 'do not'} have identical content"
s1 & s2 do have identical content

>> puts "s1 & s2 #{s1 === s2 ? 'do' : 'do not'} have identical content"
s1 & s2 do have identical content

>> puts "s1 & s2 #{s1.eql?(s2) ? 'do' : 'do not'} have identical content"
s1 & s2 do have identical content

>> puts "s1 & s2 #{s1.equal?(s2) ? 'are' : 'are not'} the same objects"
s1 & s2 are not the same objects

>> puts "s1 & s3 #{s1.equal?(s3) ? 'are' : 'are not'} the same objects"
s1 & s3 are the same objects

Seems like === is a good candidate for case-insensitive, white space-insensitive comparison…

class String
  def ===(str)
    str.is_a?(String) && self.spaceless.casecmp(str.spaceless) == 0
  end

  def spaceless
    self.gsub(/\s/, "")
  end
end

which then allows for:

>> "   fo   \t  o  " === "  f o o"
=> true

The tricky thing is, this will override how case statements are compared. I'd prefer to have the looser match in many cases, but extra care should be taken when adding this to an existing codebase. In that case, I'd define the method as String#equiv? or similar. Ideally, Ruby would let us define something like ==~, but that generates a syntax error. C'mon, Ruby!