title: visitor vs servant vs command patterns
body: <p><a href="https://en.wikipedia.org/wiki/Servant_(design_pattern)#Similar_design_pattern:_Command" rel="nofollow">Here</a> the resemblance of Command and Servant patterns is discussed. But on the other hand I see that Servant is very similar to Visitor and so much similar that I don't know what is the difference at all? Both serve for other class objects by adding functionality. But command pattern does not add functionality, instead wraps it, right? Please explain where is my confusion.</p>