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- A node-set is true if and only if it is non-empty. 一个节点当且仅当它不是空节点时，表达式的值为真。
- A string is true if and only if its length is non-zero. 字符串的值为真的充分必要条件就是字符串的长度不为零。
- Declare it as Shared if and only if you define it inside a class. 当且仅当在类中定义此过程时,才将其声明为Shared。
- Theorem 1 and are equivalent infinitesimals if and only if . 定理1与是等阶无穷小的充分必要条件为.
- Every thing has its solution, if and only if you can be farseeing. 每个问题都有其解决之道，只要你把目光放得远一点！
- The Boolean operation whose result has the Boolean value 0 if and only if each operand has the Boolean value 0. 一种布尔运算,当且仅当每个操作数都具有布尔值0时,其结果才具有布尔值0。
- A rational decision maker takes an action if and only if the marginal benefit of the action exceeds the marginal cost. 只有当这个行动带来边际利润超出它的边际成本时,一个理性的决策制定者才可以实施这个行动。
- Positive semi-definite matrices are positive definite if and only if they are nonsingular. 正半定矩阵是正定的，当且仅当它们是非奇异矩阵。
- Object variables are identical if and only if they refer to the same instance of the same class. 相同类的相同实例。
- The dyadic Boolean operation whose result has the Boolean value 0 if and only if the first operand has the Boolean value 0 and the second has the Boolean value 1. 一种二元布尔运算,在这种运算中,当且仅当第一个操作数的布尔值为0,第二个操作数的布尔值为1时,其结果的布尔值才为0。
- Two sets are said to be equivalent if and only if they can be placed in one-to-one correspondence. 当且仅当两个集合中的元素一一对应时，才称它们为等势。
- Hashes of two sets of data should match if and only if the corresponding data also matches. 两组数据的哈希值仅在相应数据也匹配时才应当匹配。
- Type object references refer to the same object if and only if they represent the same type. 对象引用当且仅当它们表示相同的类型时,才引用相同的对象。
- Numbered logfiles may be moved, but not deleted, if and only if the database file(s) are Consistent. 当且仅当数据库文件一致时,可以移动已编号的日志文件,但不能删除。
- If Char F = p > 0, L is abelian if and only if every (finite-dimensional) irreducible module of L is one-dimensional. 若charF=P>0,则L为交换当且仅当L的任一(有限维)不可约模为1维的;
- A rational decisionmaker takes an action if and only if the marginal benefit of the action exceeds the marginal cost. 如果而且只有一种行动的边际收益大于边际成本，一个理性决策者才会采取这项行动。
- The Boolean operation whose result has the Boolean value 1 if and only if each operand has the Boolean value 1. 一种布尔操作,当且仅当每个操作数的布尔值都为1时,它的结果的布尔值为1。
- A tree is balanced if and only if for every node the heights of its two subtrees differ by at most 1. 当且仅当两个子树的高度差不超过1时，这个树是平衡二叉树。（同时是排序二叉树）
- It is proved that A is an intuitionistic fuzzy subset of a group G if and only if cut sets of A are subgroup of G. 最后，讨论了直觉模糊集截集与直觉模糊子群的关系，证明了A是群G的一个直觉模糊子群的充分必要条件是A的截集是G的一个子群。
- An epistemic proposition is true if and only if it is a member of corresponding world. 一个认知命题是真的,当且仅当它属于相应的认知世界之中。
