True and false

Any Scheme value can be used as a boolean value for the purpose of a conditional test. As explained in section $[*]$ , all values count as true in such a test except for . This report uses the word ``true'' to refer to any Scheme value that counts as true, and the word ``false'' to refer to . true false

$\begin{note} In some implementations the empty list also counts as false instead of true. \end{note}$

Bartley: tighten this up.