Cprogramming 简明教程
Ternary Operator in C
C 中的三元运算符 (?:) 是一种条件运算符。术语 “三元” 暗示运算符有三个操作数。三元运算符通常用于以更简洁的方式放置多个条件（if-else）语句。
The ternary operator (?:) in C is a type of conditional operator. The term "ternary" implies that the operator has three operands. The ternary operator is often used to put multiple conditional (if-else) statements in a more compact manner.
Syntax of Ternary Operator in C
三元运算符与以下语法一起使用：
The ternary operator is used with the following syntax −
exp1 ? exp2 : exp3它使用三个 operands −
It uses three operands −
-
exp1 − A Boolean expression evaluating to true or false
-
exp2 − Returned by the ? operator when exp1 is true
-
exp3 − Returned by the ? operator when exp1 is false
Example 1: Ternary Operator in C
下面的 C 程序使用三元运算符检查变量是否为偶数或奇数。
The following C program uses the ternary operator to check if the value of a variable is even or odd.
#include <stdio.h>
int main(){
int a = 10;
(a % 2 == 0) ? printf("%d is Even \n", a) : printf("%d is Odd \n", a);
return 0;
}Example 2
条件运算符是 if-else 结构的紧凑表示。我们可以通过以下代码来改写检查奇数/偶数的逻辑 −
The conditional operator is a compact representation of if–else construct. We can rewrite the logic of checking the odd/even number by the following code −
#include <stdio.h>
int main(){
int a = 10;
if (a % 2 == 0){
printf("%d is Even\n", a);
}
else{
printf("%d is Odd\n", a);
}
return 0;
}Example 3
下面的程序比较变量 "a" 和 "b"，并将其中一个较大值分配给变量 "c"。
The following program compares the two variables "a" and "b", and assigns the one with the greater value to the variable "c".
#include <stdio.h>
int main(){
int a = 100, b = 20, c;
c = (a >= b) ? a : b;
printf ("a: %d b: %d c: %d\n", a, b, c);
return 0;
}Example 4
使用 if-else 结构所对应的代码如下 −
The corresponding code with if–else construct is as follows −
#include <stdio.h>
int main(){
int a = 100, b = 20, c;
if (a >= b){
c = a;
}
else {
c = b;
}
printf ("a: %d b: %d c: %d\n", a, b, c);
return 0;
}Example 5
如果你需要在三元运算符的 true 和/或 false 操作中输入多个语句，那么你必须用逗号将它们分开，如下所示 −
If you need to put multiple statements in the true and/or false operand of the ternary operator, you must separate them by commas, as shown below −
#include <stdio.h>
int main(){
int a = 100, b = 20, c;
c = (a >= b) ? printf ("a is larger "), c = a : printf("b is larger "), c = b;
printf ("a: %d b: %d c: %d\n", a, b, c);
return 0;
}Example 6
使用 if-else 语句的相应程序如下 −
The corresponding program with the use of if–else statements is as follows −
#include <stdio.h>
int main(){
int a = 100, b = 20, c;
if(a >= b){
printf("a is larger \n");
c = a;
}
else{
printf("b is larger \n");
c = b;
}
printf ("a: %d b: %d c: %d\n", a, b, c);
return 0;
}Nested Ternary Operator
就像我们可以使用嵌套的 if-else 语句一样，我们可以在 True 操作数和 False 操作数中使用三元运算符。
Just as we can use nested if-else statements, we can use the ternary operator inside the True operand as well as the False operand.
exp1 ? (exp2 ? expr3 : expr4) : (exp5 ? expr6: expr7)首先，C 检查 expr1 是否为 true。如果是，则检查 expr2。如果为 true，则结果为 expr3；如果为 false，则结果为 expr4。
First C checks if expr1 is true. If so, it checks expr2. If it is true, the result is expr3; if false, the result is expr4.
如果 expr1 变为 false，则它可能会检查 expr5 是否为 true，然后返回 expr6 或 expr7。
If expr1 turns false, it may check if expr5 is true and return expr6 or expr7.
Example 1
让我们开发一个 C 程序来确定一个数字是能被 2 和 3 整除，还是仅能被 2 整除，或仅能被 3 整除，还是不能被 2 和 3 整除。我们将为此使用嵌套条件运算符，如下面的代码所示 −
Let us develop a C program to determine whether a number is divisible by 2 and 3, or by 2 but not 3, or 3 but not 2, or neither by 2 and 3. We will use nested condition operators for this purpose, as shown in the following code −
#include <stdio.h>
int main(){
int a = 15;
printf("a: %d\n", a);
(a % 2 == 0) ? (
(a%3 == 0)? printf("divisible by 2 and 3") : printf("divisible by 2 but not 3"))
: (
(a%3 == 0)? printf("divisible by 3 but not 2") : printf("not divisible by 2, not divisible by 3")
);
return 0;
}检查不同的值 −
Check for different values −
a: 15
divisible by 3 but not 2
a: 16
divisible by 2 but not 3
a: 17
not divisible by 2, not divisible by 3
a: 18
divisible by 2 and 3Example 2
在此程序中，我们针对相同目的使用了嵌套 if-else 语句代替条件运算符 −
In this program, we have used nested if–else statements for the same purpose instead of conditional operators −
#include <stdio.h>
int main(){
int a = 15;
printf("a: %d\n", a);
if(a % 2 == 0){
if (a % 3 == 0){
printf("divisible by 2 and 3");
}
else {
printf("divisible by 2 but not 3");
}
}
else{
if(a % 3 == 0){
printf("divisible by 3 but not 2");
}
else {
printf("not divisible by 2, not divisible by 3");
}
}
return 0;
}当你运行这段代码时，它将产生以下输出：
When you run this code, it will produce the following output −
a: 15
divisible by 3 but not 2