Minor correction and clarification.

Doc/lib/liboperator.tex

@@ -59,7 +59,9 @@ core defines this operation.  The result is affected by the
 \end{funcdesc}
 
 \begin{funcdesc}{truth}{o}
-Return \code{1} if \var{o} is true, and 0 otherwise.
+Return \constant{True} if \var{o} is true, and \constant{False}
+otherwise.  This is equivalent to the constructor of the \class{bool}
+constructor.
 \end{funcdesc}