A CTree = (Node x [CTree]) is a Node associated with a list of subtrees called branches.
Tree normalizeAddTerm(Tree t)
Compute the Add-Normal form of a term t.
Tree normalizeDelay1Term(Tree s)
Compute the normal form of a 1-sample delay term s'.
Tree normalizeFixedDelayTerm(Tree s, Tree d)
Compute the normal form of a fixed delay term (s).
