This is a version of ant that has been customized to demonstrate
multithreading and strong typing.  Ant now has a function called
(if ...) which takes a boolean value.  Based on that value, it
either evaluates and returns its second or third argument. 

Booleans include food ahead, food behind, food to the right,
or food to the left.

This code runs great on an Alpha machine running digital Unix 4.0;
I can't vouch for anything else.
