1.2 KiB
1.2 KiB
title | localeTitle |
---|---|
Short-Circuit Evaluation | 短路评估 |
短路评估
仅当第一个参数不足以确定表达式的值时,短路评估才包括检查或执行第二个参数。
您可以使用&&和||进行短路评估运营商。
&&运算符的示例:
canOpenFile(filename) && openFile(filename); // If you can open the file then open it.
上面的例子相当于:
if ( canOpenFile(filename) ) {
openFile(filename);
}
示例包含||运营商:
isServerOn || startServer(); // If the server is not on then start it.
The example above is equivalent to:
if ( !isServerOn ) {
startServer();
}
Keep it all together in real example
#include <stdio.h>
#include <stdlib.h>
char *getName();
int main(int argc, char *argv[]) {
// Get first argument passed via terminal
char *name = argv[1];
// If name is not passed via terminal then print message and then get the name
name || printf("Please give me your name:") && (name = getName());
printf("Hello %s\n", name);
}
char *getName() {
// Allocate memory
char *name = malloc(30);
scanf("%s", name);
return name;
}