c - 宏 c 编程 #define min(a,b) (a < b ? a : b)

Question

我正在阅读宏，我想知道这个#define 是做什么的？我不明白“？” 和“：”。是不是说如果一个

#define min(a,b) (a < b ? a : b)

Answer 1

这不是宏特性，而是核心 C 特性，称为条件运算符的三元运算符。

x = a < b ? a : b

本质上是：

if (a < b)
   x = a
else
   x = b

即：(cond ? a : b)具有aifcond为 true 的值，否则为b。

Answer 2

The ? has nothing to do with macros, it's an Ternary Operator. It is similar to the if-else operator.

A simple example:

c = (a < b ? a : b)

This code says that when a<b is true, a is assigned to c, if a<b is false b is asigned to c. You can read more by googling "Ternary operator".