Clarifications, etc.:
<ul>
<li>The note at the bottom of the description means that your <i>tests.c</i> should not test assignment to variables. Note that you <b>do</b> need to test assignment in your own code, just do not include such a test in the version of tests.c that you submit.
<li>The original files contained object code (for buggy
	implementations you can test against) compiled for 32-bit
	architectures. p4.tar.gz has been replaced w/ p4-1.tar.gz,
	which contains object code compile for the grace machines
	(which are 64-bit).
<li>The project description for minusOperator initially said "Subtract
	left sub-tree from right". This is backwards. Subtract right
	from left (and for divide as well).
<li>A binary version assocMemory.o is in ~/212files on grace.
<li>You have some latitude about when to detect error
	conditions. createOperatorNode(), for example, does not
	necessarily have to sanity check its inputs (non-null left and
	right, for example). However, these clearly have to be checked
	before any tree is evaluated or simplified.

</ul>