Wednesday, May 03, 2006

Good Hungarian

We are used to think of hungarian notation as being a bad thing.  However, not many people know that what we know as hungarian notation is a perverted version of the original pure and good hungarian notation.  Joel Spolsky talks about that too.

-hungarian is when you prefix a variable name with type information


  fWidth = fSize

the 'f' simply means float. 

You can see you have type compatibilty on both sides, but it doesn't say anything about semantic compatibility. fWidth could be used as a measure expressed in metres, whereas fSize is expressed in feet!

Good-hungarian is when you prefix a variable name with semantic information

   mtrWidth = ftSize


   metric_width = feet_size

you can see immediately that there is a problem there. 

Both variables are of the same type (Float), yet they have a different meaning.  The prefix difference make the error stand out clearly.

This is very useful in general, but I would argue that in ruby - with the dynamism offered by duck typing - good hungarian is very useful and we already use, without even thinking about it.

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