This version of Learn Prolog Now! embeds SWI SH , SWI-Prolog for SHaring. The current version rewrites the Learn Prolog Now! HTML on the fly, recognising source code and example queries. It is not yet good at recognising the relations between source code fragments and queries. Also Learn Prolog Now! needs some updating to be more compatible with SWI-Prolog. All sources are on GitHub:
LearnPrologNow LPN SWISH Proxy SWISH

We are pleased to announce that Learn Prolog Now! is now available in book form: on 15 June 2006 it was published by College Publications as Volume 7 of their Texts in Computer Science series.

Learn Prolog Now has been available as a web-book since 2001. Over this period we have received numerous requests for a real hold-in-your-hands version of LPN! (that is, what is technically known as a ‘book’!). Well, we've finally produced such a thing, but we've done more than that. While preparing it, we took the opportunity to make extensive changes and improvements. The most important are the following:

  • We have rewritten a number of crucial sections. In particular, we have lengthened and improved our discussion of unification, proof search, recursion, termination, and DCGs.
  • We have made numerous small corrections and changes throughout the text (thanks to the many readers who pointed out errors and infelicities).
  • We took the opportunity to get rid of non-ISO constructs used in the web-book.
  • We added a Preface (telling a little about the history of LPN!) and an introduction (which discusses Prolog from a more general perspective). We also added an appendix briefly discussing some other books on Prolog that we liked.
  • We added new exercises, worked them all, and put all the answers into an appendix.

So, there you have it: LPN!, the handheld version.

Order the book at:,,,,,, Barnes and Noble, or

Click here for a BibTeX entry. And click here for a list of errata.

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© 2006-2012 Patrick Blackburn, Johan Bos, Kristina Striegnitz