Tagged Index (Part 2)

There is another design decision that I forgot to discuss in the previous Tagged Index blog entry: the meaning of the free tag. There are a number of cases that this tag could cover:

• A book may be distributed freely and not sold. There are currently no books in the Haskell books index like this.
• A book may be distributed freely as well as sold, including books with a minimum price of free. An example is Mark Watson’s Haskell Tutorial and Cookbook.
• A book may have print books for sale while distributing electronic versions freely. For example, Bob Harper provides a free PDF of his Practical Foundations for Programming Languages textbook.
• An electronic version of a book may be provided for a book that is out of print. An example is Simon Peyton Jones’s The Implementation of Functional Programming Languages.
• A book may have print and electronic versions for sale while providing a way to read the book online in a browser. There are many of these, including Haskell in Depth, Learn You a Haskell for Great Good!, and Real World Haskell.
• Source code may be available for a book that is (otherwise) not available for free. An example is Sandy Maguire’s Algebra Driven Design.

After much deliberation, I decided to associate the free tag with any book that can be read for free online. This covers all of the above cases except for the last one. The source code case is not included because I imagine that many people do not have the resources and/or knowledge to easily build the book themselves.