Befunge-93 interpreter in Ruby
Written for Ruby Quiz #184

Message from my quiz submission on ruby-talk mailing list:

Subject: Re: Befunge (#184)
From: Jeff Dallien <jeff dallien.net>
Date: Sun, 30 Nov 2008 07:29:28 +0900

Here is my solution. It's not a revolutionary implementation, but I
had an emphasis on readability and testing. I believe it correctly
runs all the example programs from the Befunge-93 site that the C
reference implementation does.

While debugging I had a "C interpreter mode" which did a few things
slightly differently such as division and mod with negative numbers to
match the behaviour of the reference implementation. I eventually
removed it for clarity since it didn't gain much, other than
accounting for those differences.

For example, the following program will output -1 when run with the C
implementation and -2 with a standard Ruby implementation. Solutions
to Ruby Quiz #85 have some methods which provide C-like division and
mod.

3-2/.@

I couldn't find a simple solution for single character input, so it
goes without. Thus for programs like namegame.bf you have to hit enter
between each character.

Spec file is below the source. Thanks for the interesting quiz.

Jeff Dallien
http://jeff.dallien.net/