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bb_update/3
bb_update(:Key, -OldTerm, +NewTerm)
If a term is currently stored under Key and unifies with
OldTerm, then the term is replaced by a copy of NewTerm.
Otherwise, bb_update/3
silently fails. This predicate provides
an atomic swap operation.
bbkey
term
term
Any uninstantiated variables in the Term will be replaced by brand new, unattributed variables (see ref-sem-sec).
instantiation_error
Key is not instantiated
type_error
Key is not an atom or a small integer.