Basic Pascal Tutorial/Chapter 3/Boolean Expressions/zh CN: what changed
Revision 2 to 3. Removed lines have a minus sign; added lines have a plus sign.
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| 1 | 1 | 3B - 布尔表达式 (原作者: Tao Yue, 状态: 未更改) | |
| 2 | 2 | ||
| 3 | 3 | [[Boolean/zh CN|布尔表达式]] 用于比较两个值，得到 `真` 或者 `假`： | |
| 4 | 4 | ||
| 5 | - | ||
| 5 | + | ``` | |
| 6 | + | 值1 关系运算符 值2 | |
| 7 | + | ``` | |
| 6 | 8 | ||
| 7 | 9 | 使用以下关系运算符： | |
| 8 | 10 | ||
| 9 | - | ||
| 10 | - | ||
| 11 | - | ||
| 12 | - | ||
| 13 | - | ||
| 14 | - | ||
| 11 | + | ``` | |
| 12 | + | < 小于 | |
| 13 | + | > 大于 | |
| 14 | + | = 等于 | |
| 15 | + | <= 小于等于 | |
| 16 | + | >= 大于等于 | |
| 17 | + | <> 不等于 | |
| 18 | + | ``` | |
| 15 | 19 | ||
| 16 | 20 | 你可以将运算结果赋值给变量，这里我们将一个 `真` 赋值给 some_bool。 | |
| 17 | 21 | ||
| 18 | - | ||
| 22 | + | ``` pascal | |
| 23 | + | some_bool := 3 < 5; | |
| 24 | + | ``` | |
| 19 | 25 | ||
| 20 | 26 | 逻辑运算符： | |
| 21 | 27 | ||
| 22 | - | ||
| 23 | - | ||
| 24 | - | ||
| 25 | - | ||
| 28 | + | ``` | |
| 29 | + | not 逻辑非 (~) | |
| 30 | + | and 逻辑与 (^) | |
| 31 | + | or 逻辑或 (v) | |
| 32 | + | xor 逻辑异或 | |
| 33 | + | ``` | |
| 26 | 34 | ||
| 27 | 35 | `NOT`是一元运算符，用于取反。 | |
| 28 | 36 | ||
| 29 | 37 | - not 真 = 假 | |
| 30 | 38 | - not 假 = 真 | |
| 31 | 39 | ||
| 32 | 40 | `AND`，当两个值都为真是，结果为真，否则为假。 | |
| 33 | 41 | ||
| 34 | 42 | - 真 and 假 = 假 | |
| 35 | 43 | - 真 and 真 = 真 | |
| 36 | 44 | ||
| 37 | 45 | `OR`，当有一个值为真时，结果为真，否则为假。 | |
| 38 | 46 | ||
| 39 | 47 | - 真 or 真 = 真 | |
| 40 | 48 | - 真 or 假 = 真 | |
| 41 | 49 | - 假 or 真 = 真 | |
| 42 | 50 | - 假 or 假 = 假 | |
| 43 | 51 | ||
| 44 | 52 | `XOR`，任一值为真时，结果为真，但不能同时是，从而： | |
| 45 | 53 | ||
| 46 | 54 | - 真 xor 真 = 假 | |
| 47 | 55 | - 真 xor 假 = 真 | |
| 48 | 56 | - 假 xor 真 = 真 | |
| 49 | 57 | - 假 xor 假 = 假 | |
| 50 | 58 | ||
| 51 | 59 | 当关系运算符和逻辑运算符混合使用时，要小心使用括号。 | |
| 52 | 60 | ||
| 53 | 61 | ``` pascal | |
| 54 | 62 | (3>5) or (650<1) | |
| 55 | 63 | ``` | |
| 56 | 64 | ||
| 57 | 65 | `逻辑运算符` 优先级高于 `关系运算符`： | |
| 58 | 66 | ||
| 59 | 67 | 1. not | |
| 60 | 68 | 2. * / div mod and | |
| 61 | 69 | 3. \+ - or | |
| 62 | 70 | 4. \< \> \<= \>= = \<\> | |
| 63 | 71 | ||
| 64 | 72 | 所以，`3 > 5 or 650`，运算时，是这样：`3 > (5 or 650)`，但这样没有意义，因为整数不适用逻辑运算。 | |
| 65 | 73 | ||
| 66 | 74 | 逻辑运算符（`AND、OR、NOT、XOR`），可以很容易在逻辑表达式上使用。 | |
| 67 | 75 | ||
| 68 | 76 | 如有可能，不要使用等号比较2个实数，因为，小数位会导致它们不相等。 | |
| 69 | 77 | ||
| 70 | 78 | | | | | | |
| 71 | 79 | |----|----|----| | |
| 72 | 80 | | [[Basic Pascal Tutorial/Chapter 3/Sequential control/zh CN|上一页]] | [[Basic Pascal Tutorial/Contents/zh CN|目录]] | [[Basic Pascal Tutorial/Chapter 3/IF/zh CN|下一页]] | | |
| 73 | 81 | ||
| 74 | 82 | --- | |
| 75 | 83 | *From the Free Pascal wiki, page "Basic Pascal Tutorial/Chapter 3/Boolean Expressions/zh CN", as it stood on 2022-08-20 after a change by Kai Burghardt, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).* |