Logic Programming in Clojure | Hacker News Reader

Logic Programming in Clojure

intensivesystems.net

46 pointscubix8 comments

Besides The Reasoned Schemer, another excellent logic programming book is _The Art of Prolog_ by Sterling and Shapiro. While it uses Prolog rather than Lisp, it's overall focus is more on Logic Programming than Prolog specifically. It starts with the big ideas in Logic Programming and what they're theoretically capable of, and then shifts to Prolog, the most mainstream implementation of an LP language, and the design trade-offs it has made. (There are other great books more specific to Prolog, if you find you like it.)

Also, it has been out of print for a while, and the second edition can be pretty expensive ($90-100ish used). The first edition is much cheaper ($2-5), and while the second covers a newer version of Prolog and greatly expands on the "projects in Prolog" chapters, the first still covers the core LP concepts pretty well.

Strongly seconded - I started with The Art of Prolog a few months ago and also enjoyed it. Having seen both, I think I'll probably go through the Reasoned Schemer and then return to the Art of Prolog.

A list can be defined using square-brackets, '[' and ']'.

I thought it was funny to do this in Lisp and not represent lists with parens, but I guess it's only syntatic sugar anyway.

A list is represented with parens. [] is a vector. There are behavior and performance differences between lists and vectors.

I don't quite follow, but I'm also new to mini-Kanren. They're called lists in the article and said "to group values or variables so that the collection may referred to as a unit", which sounds like a generic list to me. He compares them to Lisp lists just a couple paragraphs lower. Could you elaborate please?

Most likely it's a "list" in the DSL, but implemented using Clojure's vectors, which are represented with square brackets and have convenient evaluation semantics (items are evaluated, but it's not a function call), so that it's much more common to use vectors in clojure where one would often type (list foo bar) in CL or perhaps Scheme.

Often vectors are used in Clojure DSLs to differentiate from the "operator syntax" which uses actual lists. There are some exceptions in even clojure.core macros, but often you can assume that any unquoted list is evaluated as a function or macro call, even if it is a macro parameter.

K, upvoted simply for mentioning The Reasoned Schemer, a book that I'm having great fun simply picking up occasionally. Time to really start cranking on it.

The port of mini-Kanren to Clojure is a great contribution - thanks!

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