go-rodrego

This is a reimplementation of the RodRego register machine in Go, and hopefully performs the same computations as the version from Tufts, which is available for download and on GitHub as well.

To understand register machines and what's going on generally, take a look at Dan Dennett's The Secrets of Computer Power Revealed, or his very nice book "Intuition Pumps and Other Tools for Thinking".

I made go-rodrego mostly just as a small exercise for learning Go, but also because the Tufts version seems to be in RealBASIC (now called Xojo apparently) and I couldn't figure out how to make it go on Linux without downloading... uh... Xojo.

Anyway! This is a tiny interpreter for the RodRego register machine, and I hope somebody will find it interesting.

installation

You'll need Go installed already -- I have Go release 1.2.1 on Ubuntu, but later versions will probably work.

Get the package like so:

$ git clone https://github.com/alexrudnick/go-rodrego.git

Then build:

$ cd go-rodrego
$ go build rodrego.go

And there you go! You can now run ./rodrego

running RodRego programs

You can specify both the program to run and the initial state of the registers with names of files on the command line.

• The -program argument (obligatory) is for specifying the RodRego program to run. Give it a filename.
• The -values argument (optional) is for specifying the initial state of the registers for the register machine.
• The -step flag makes the interpreter step through a program one instruction at a time.

For example:

$ ./rodrego -program testprograms/add.rgo -values values.txt

This will run the add.rgo file with initial register values set by values.txt. If your values.txt looks like this:

2 10
3 5

... (which sets register 2 to have value 10, and register 3 to have value 5), then the end result should be their sum, 15, in the output register.

file formats

The official RodRego ships with sample programs that have old-style (pre-Mac OS X) Mac line endings; just a carriage return character, rather than the more familiar Unix/Mac line endings (line feed) or DOS/Windows-style CRLF.

go-rodrego supports programs with any of these line endings, which is slightly interesting because the Go standard library routines don't expect by default to see old-style Mac line endings.

rodrego programs

To learn how these programs work, take a look at Dan Dennett's excellent The Secrets of Computer Power Revealed. He does a fabulous job of explaining what's up here.

RodRego programs have one instruction per line, of the form LINENUMBER INSTRUCTION ARGUMENTS. Instructions can be one of INC, DEB or END (any case is fine).

• INC takes two arguments, a register number to increment and a line to jump to next.
• DEB is "decrement or branch", and it takes three arguments: the register number to degrement, a line number to jump to if that can be done, and a line number to jump to if the register is already at 0. This is the only way to do a conditional branch in the language.
• END ends the program.

Line numbers are canonically natural numbers in base-10, but in this implementation you can actually use any kind of label as long as it doesn't have whitespace in it. You could use aubergine as a line number if you want.

Also comments are a thing; a line where the first non-whitespace character is a # is treated as a comment.

register values

One register can be set per line; put the register number and then its value.

Both must be base-10 nonnegative integers.

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OK, that's it! Have fun!