TreeContext.TreeSourceThe module for trees
pp ppf fmt t pretty prints the tree t on the formatter fmt using the pretty printer for tree nodes ppf
fold_depth_first (f,g) t recursively computes (g a) b_1 .... b_n where a=f t_0 and b_i= f t_i and t is a tree of node t_0 and of children t_1...t_n