条件?a:b与result = value1 if condition else value2区别
时间: 2024-05-25 17:18:27 浏览: 13
条件表达式a:b和result = value1 if condition else value2的主要区别在于它们的语法和用法。
- 条件表达式a:b的语法简单,它用于在一行代码中根据条件选择一个值。它的语法是condition为真时返回a,否则返回b。例如:x = 5 if a > b else 10
- result = value1 if condition else value2是一个三元运算符,它允许根据条件选择两个不同的值之一,并将其分配给变量result。它的语法是,如果条件为真,则将value1赋给result,否则将value2赋给result。例如:result = "Yes" if x > y else "No"
总之,条件表达式a:b用于选择一个值,而result = value1 if condition else value2用于根据条件选择并赋值给变量。
相关问题
select case when null = null then 1 when null < > null then 2 else 3 end result_value from dual;
The result of this query would be 1.
Explanation:
- The first condition "null = null" is evaluated as true.
- The second condition "null < > null" is evaluated as null, because any comparison with null results in null.
- Since the second condition is not true, the query moves on to the "else" clause and returns 3.
常用C语言与汇编语言之间的对应关系:if else;switch;条件表达式;while;for
下面是常用C语言与汇编语言之间的对应关系:
1. if else:
C语言代码:
```
if (condition) {
// do something
} else {
// do something else
}
```
汇编语言代码:
```
; assume condition is in register eax
cmp eax, 0 ; compare eax with 0
je else ; jump to else if eax is 0
; do something
jmp end_if
else:
; do something else
end_if:
```
2. switch:
C语言代码:
```
switch (expression) {
case value_1:
// do something
break;
case value_2:
// do something
break;
default:
// do something else
break;
}
```
汇编语言代码:
```
; assume expression is in register eax
cmp eax, value_1
je case_1
cmp eax, value_2
je case_2
jmp default_case
case_1:
; do something
jmp end_switch
case_2:
; do something
jmp end_switch
default_case:
; do something else
end_switch:
```
3. 条件表达式:
C语言代码:
```
result = condition ? value_if_true : value_if_false;
```
汇编语言代码:
```
; assume condition is in register eax
cmp eax, 0 ; compare eax with 0
je false_case ; jump to false_case if eax is 0
mov result, value_if_true ; move value_if_true to result
jmp end_conditional
false_case:
mov result, value_if_false ; move value_if_false to result
end_conditional:
```
4. while:
C语言代码:
```
while (condition) {
// do something
}
```
汇编语言代码:
```
start_while:
; assume condition is in register eax
cmp eax, 0 ; compare eax with 0
je end_while ; jump to end_while if eax is 0
; do something
jmp start_while ; jump back to start_while
end_while:
```
5. for:
C语言代码:
```
for (initialization; condition; increment) {
// do something
}
```
汇编语言代码:
```
initialization ; initialization code
start_for:
; assume condition is in register eax
cmp eax, 0 ; compare eax with 0
je end_for ; jump to end_for if eax is 0
; do something
increment ; increment code
jmp start_for ; jump back to start_for
end_for:
```
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