Compile: erlc tarry.erl

Run: erl -noshell -run tarry -run init stop < input.txt

An undirected network of processes.

Initially, an initiator sends out a token.

• Rule 1: A process never forwards the token through the same channel twice.

• Rule 2: A process only forwards the token to its parent when there is no other option.

The token travels through each channel both ways, and finally ends up at the initiator.