Conduit_trieSourceRadix tree that can do longest-prefix searches on string keys
Radix tree that maps string keys to 'a values
insert key value tree returns a new tree with the mapping key to value
longest_prefix key tree finds the key k which shares the longest prefix with key and returns the associated value.
fold f initial t folds f over all bindings in t
is_prefix a b returns true if a is a prefix of b