Functional completeness 自足算子
In logic, a functionally complete set of logical connectives or Boolean operators is one which can be used to express all possible truth tables by combining members of the set into a Boolean expression. A well-known complete set of connectives is { AND, NOT }, consisting of binary conjunction and negation. The singleton sets { NAND } and { NOR } are also functionally complete.
，这里的 
是一个任意集合而 
是一个通用的 2-元素集合，典型为 
，特别是生成所有的有限布尔函数，
。