Thursday, April 11, 2013

This Seems Irrational... But... HamCalc

Step 1.  Look at the original HamCalc.  Even if you aren't interested in Ham radio, it's an epic, evolving achievement in a specialized kind of engineering support.  It's a repository of mountains of mathematical models, some published by the ARRL, others scattered around the internet.

Step 2.  Look closely at HamCalc.  It's all written in GW basic.  Really.  The more-or-less final update is from 2011 -- it's no longer an active project -- but it's a clever idea that suffers from a horrible constraint imposted by the implementation language.

A long time ago, I was captivated by the idea of rewriting HamCalc as Java Applets.  It seemed like a good idea at the time, but that's a lot of work: 449 programs, 85,000 lines of code.

Recently, I wanted to make some additional use of HamCalc's amazing collection of formulas.

However.  The distribution kit is rather hard to read.  The .BAS files are in the tokenized "binary" format.

I found a Python project to interpret the byte codes into a more useful format. See http://www.danvk.org/wp/gw-basic-program-decoder/  However, it wasn't terribly well written, and didn't prove completely useful.

GW Basic Bytes Codes

Look at http://www.chebucto.ns.ca/~af380/GW-BASIC-tokens.html for some basic rules on the file format.

See http://www.antonis.de/qbebooks/gwbasman/index.html for a reasonably clear definition of the language itself. Quirks are, of course, studiously ignored, so there's a lot of ambiguity on edge cases.

For simple bytes-to-text translation, this is pretty simple.  The next step -- interpreting GW Basic -- is a bit more complex.

Future

The irrational thing is that I'm captivated by the idea of preserving this legacy gift from the authors in another, more useful language. Indeed, the idea of a community of "HamCalc Ports to Other Languages" appeals to me. This base of knowledge is best preserved by being made open so that it can be rewritten into other commonly-used languages.

There's a subset version here: http://www.softpedia.com/get/Science-CAD/HamCalc.shtml and here http://www.dxzone.com/dx11432/hamcalc-v1-3.html. This is just a few of the calculations, carefully rebuilt to include nice versions of the ASCII-art graphics that are central to the original presentation.

The hard part of preserving HamCalc is the absolute lack of any test cases of any kind.

I think the project should work like this.

  1. Publish the complete plain text source decoded from the tokenized binary format. It will likely be somewhere on http://www.itmaybeahack.com/ or perhaps a Dropbox.
  2. Publish the index of programs and features as a cross-reference to the various programs. This should include the various links and references and documentation snippets that populate the code and output. This forms the backbone of the documentation as well as the unit testing.
  3. Do a patient (and relatively lame) translation to Python3.2 to break HamCalc into two tiers. The calculation library and a simple UI veneer using stdio features of the print() and input() statements. The idea is to do a minimalist rewrite of the core feature set so that a GUI can be laminated onto a working calculation library.
  4. Work out test cases for the initial suite of 449 legacy programs oriented toward the calculation layer, avoiding the UI behavior. The idea isn't 100% code coverage. The idea is to pick the relevant logic paths based on the more obvious use cases.
A sophisticated GUI is clearly something that was part of the original vision. But the limitations of GW Basic and tiny computers of that era assured that the UI and calculation were inextricably intertwingled.

If we can separate the two, we can provide a useful library that others can build on.

Maybe I should organize http://www.hamcalc.org/ as the jumping-off point for this effort?