[Mini Kanren] Benchmarking different substitution data structures
In logic programming, a substitution is a mapping from logic variables to values (including other logic variables). Logic programs are composed of goals, with the type signature Subst => Subst* — i.e. it might fail (thus generating 0 possible substitution), succeed once, or succeed multiple times, or even an infinite number of times. It is necessary for substitutions to behave as values — if you take a substitution, and add a binding, you better get a new substitution, rather than do the modification in place, because that substitution might be used by other goals. In Lisp, the traditional data structure for this is the associat

Gnoetry 1-2-3
I’ve been fascinated with Jon Trowbridge and Eric Elshtain’s Gnoetry for quite some time, but have until recently contented myself with watching from the sidelines. There are several reasons — being busy with other projects, and mostly that the code is rather well-hidden from the public eye; there is a Subversion repository, but one has to jump through some hoops to get to it (I forgot how I got to the code; I think I might have emailed Jon about it). After you get the code, there’s still the matter of setting things up. And SVN is a rather messy

Discovering Rosetta Code
I discovered Rosetta Code over the weekend. It bills itself as a programming chrestomathy [wp] site, offering a place to learn, compare and contrast different programming languages by reading and writing solutions to different programming tasks. So far, I’ve been using it to brush up on my Clojure, Pure and Scala fu. I’ve just added the Pure category, so the examples are a bit sparse still. If you want to see the so

[Packaging] Ships that pass in the night
Amusing (or depressing?) trail of bug-hunting: During the package review process for pure, we discovered that a dlsym-ed strcmp does not produce the right result on F-12 The same problem turned out to be the case with avahi-sharp; its dlsym-ed strlen produces incorrect results, causing segmentation faults in Banshee (which uses it through mono-zeroconf) Switching zeroconf to use avahi through DBUS would fix things, but when poking through the sources, it is discovered that its developer has been bundling a private copy of NDesk.DBus, against Fedora guidelines and the wishes of NDesk.DBus upstream Said u

Mini Kanren: updates
Several updates to Mini Kanren, covering syntax, semantics and documentation. SyntaxImplicit conversions now allow you to write the more idiomatic x === y to mean mkEqual(x,y) . Likewise, you can use x =/= y to mean neverEqual(x,y) (see below for explanation). SemanticsThe =/= (neverEqual) goal has been added, specifying that x and y should never be unified with each other. This requires reworking the substitution system; previously, a substitution is simply a list of var -> x mappings, together with assorted functions. Supporting neverE