Register machine

An implementation of a register machine with three instructions: increment, decrement, and halt.

Usage

python3 machine.py input_file.reg

Input file structure

The first line needs to be an initial configuration. This is a tuple whose 0th element is the label of the first instruction, and subsequent elements are initial register values. For example, (0, 0, 2, 4) means the first instruction is label 0 and the registers start with the values (r0, r1, r2) = (0, 2, 4).

All parsed lines after this are instructions. Instructions start with a label (which can be made up of any ASCII characters except colons and whitespace characters such as spaces and line breaks), followed by a colon (:), and then the instruction.

Instructions

The possible instructions are:

• halt: proper halt
• inc(rx), i: increment register x and then go to instruction with label i
• dec(ry), i, j: if register y > 0 then decrement it and go to instruction i, otherwise go to instruction j.

Comments and blank lines

Blank lines are ignored, as are comment lines starting with #.

Machine output

The machine outputs every operation in the comma-separated format Execution Number, Instruction Label, Register State.

Set the SHOW_TRACE constant in machine.py to False to only see the final state after the program has terminated and not every operation along the way.

Examples

See the examples directory in this repo for examples.