Thank you for your comment; what’s up?

Actually, I’ve already downloaded and installed Qi II (on GNU CLISP 2.45), and followed part of the “Qi for the ML Programmer” tutorial (see http://www.lambdassociates.org/qiml.htm). The reason that I haven’t posted a blog entry on it is that I had been trying to learn enough of it to write a version of Towers of Hanoi, properly commented, in it to post, but with my special assignment, just didn’t have enough time.

Qi seems to be a fascinating language. Although it is built on top of Common Lisp, it actually seems to be more of a hybrid of Scheme and Haskell. What is intriguing about Qi is that the language is just semantically similar enough to Haskell to achieve a symbiotic pedagogical relation for the student; i.e., learning Qi helps to elucidate Haskell concepts, and vice-versa.

Another language that I just discovered two days ago, and am currently experimenting with, is Refal, an abbreviation for “Recursive Functions Algorithmic Language” (see http://www.refal.net/index_e.htm). Refal was designed by Valentin Turchin (see http://pespmc1.vub.ac.be/TURCHIN.html), a Russian emigrant, currently Professor Emeritus of Computer Sciences at the City College at the City University of New York. Refal is a functional programming language with pattern matching oriented toward symbol manipulation, wherein the pattern matching works forwards, unlike in Prolog, wherein it works backwards.

An example of a simple Refal function to determine whether a given string is a palindrome is as follows:

Pal { = True;
s.1 = True;
s.1 e.2 s.1 = ;
e.1 = False; }

The above-mentioned code defines a function Pal, which executes a sequence of pattern-matching statements. Basically, it reads as follows (where s.1 is a free variable matching any symbol consisting of a single character, e.2 is a free variable matching any expression, and the angle-brackets “<>” are used to delimit a function call within):

If a string is blank, then return True;
else if the string consists of only one character, then return True;
else if the string consists of only one character, followed by any expression, followed by the same one character, then call Pal recursively on the expression;
else if the string consists of any other expression, then return False.

Elegant, don’t you think? One aspect of Pal that I really like is the fact that it is based on symbol manipulation, rather than numerical computation. One of my dreams is one day to design a functional program that can pass the Turing Test, and for that, symbol manipulation seems more relevant than numerical computation.

A version of Refal-5 for win-32 is bundled with SciTE in a package called “Refal-SciTE,” downloadable in a self-installing installer at the Web site “Integrated cover for program developing” (http://www.refal.net/~belous/refsci-e.htm) (the download page, linked to from that page, is http://www.refal.net/~belous/download-refalscite.htm).

I’ll write about both Qi II and Refal-5 as soon as I find time. Thanks for commenting! ]]> http://www.dekudekuplex.org/2008/11/18/towers-of-hanoi/comment-page-1/#comment-6 Benjamin L. Russell Wed, 24 Dec 2008 02:50:51 +0000 http://www.dekudekuplex.org/?p=3#comment-6 Oops, you’re absolutely right! Sorry. I’ll correct that right now…. Oops, you’re absolutely right! Sorry. I’ll correct that right now….