Topic: hash merge and update  I basically need to add an key and
value pair to an hash based on condition. The following code
works.  result = expr > value ? 100: nil  if (!result.nil?)   
 hash.update({ :key3 => value3  How can i do that succintly?
what is the difference between merge and update?  Re: hash merge
and update  You can do this:  hash[:key] = 100 if exp > value
Merge and update are very similar, the only difference is
"merge" returns a new hash result, update changes the hash in
place. So "merge!" with the exclemation mark is the same as
"update".  Railscasts - Free Ruby on Rails Screencasts