c - 为什么 -- 运算符在执行时不从值中减去？

Question

这个问题已经有答案了:

What is the difference between prefix and postfix operators? (13 个回答)

已关闭 8 年前。

为什么减运算符是--执行时没有将值减 1？

int a = 20;
int c ;

c = a--;

检查 c 的值现在应该是 19，但结果却是 20。我错过了什么？

Answer 1

a-- 是后递减，您需要 --a 预递减。请阅读 Wiki 上的自增和自减运算符

The following C code fragment illustrates the difference between the pre and post increment and decrement operators:

int  x;
int  y;

// Increment operators
x = 1;
y = ++x;    
// x is now 2, y is also 2
y = x++;
// x is now 3, y is 2

// Decrement operators
x = 3;
y = x--;    
// x is now 2, y is 3
y = --x;    
// x is now 1, y is also 1