
















%   Purpose: Flatten various binary trees to lists and convert back.

/*  This file was originally for PRESS, where you often want to take
    a tree such as 1+x+0+(u*v+9)+(x^2+2) and flatten it to a list
    such as [1,x,u*v,9,x^2,2] so that you can easily pick out all the
    constants or all the terms involving x or something, without having
    to write N different sets of predicates to handle N different
    binary operators.  It c























































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































