Branch Store
find r b is Some c iff c is bound to b in t. It is None if b is not present in t.
get t b is similar to find but raise Invalid_argument if b is not present in t.
watch t b f calls f on every change in b.
Make_ext.BranchManipulate branches.
find r b is Some c iff c is bound to b in t. It is None if b is not present in t.
get t b is similar to find but raise Invalid_argument if b is not present in t.
watch t b f calls f on every change in b.