Declarative programming vs. Imperative programming
- by EpsilonVector
I feel very comfortable with Imperative programming. I never have trouble expressing algorithmically what I want the computer to do once I figured out what is it that I want it to do. But when it comes to languages like SQL or Relational Algebra I often get stuck because my head is too used to Imperative programming.
For example, suppose you have the relations band(bandName, bandCountry), venue(venueName, venueCountry), plays(bandName, venueName), and I want to write a query that says: all venueNames such that for every bandCountry there's a band from that country that plays in venue of that name.
In my mind I immediately go "for each venueName iterate over all the bandCountries and for each bandCountry get the list of bands that come from it. If none of them play in venueName, go to next venueName. Else, at the end of the bandCountries iteration add venueName to the set of good venueNames".
...but you can't talk like that in SQL and I actually need to think about how to formulate this, with the intuitive Imperative solution constantly nagging in the back of my head. Did anybody else had this problem? How did you overcome this? Did you figured out a paradigm shift? Made a map from Imperative concepts to SQL concepts to translate Imperative solutions into Declarative ones? Read a good book?
PS I'm not looking for a solution to the above query, I did solve it.
