c - 从 double 到 int 的隐式类型转换？

Question

// Assuming these definitions
int x; 
float y;

这有什么区别:

  x = y = 7.5;

和这个:

  y = x = 7.5;

为什么第一个打印 y值为 7.5 ,
和第二个打印 y如 7.00 ?

Answer 1

解释很简单:=从右到左关联，这意味着 x = y = 7.5;被评估为 x = (y = 7.5);因此本质上与:

y = 7.5;   // value is converted from double to float, y receives 7.5F
x = y;     // value of y is converted from float to int, x receives 7 (truncated toward 0)

而 y = x = 7.5;被评估为 y = (x = 7.5); :

x = 7.5;   // 7.5 is converted to int, x receives value 7 (truncated toward 0)
y = x;     // value of x is converted to float, y receives 7.0F

这些隐式转换可能违反直觉。您可能希望提高警告级别，让编译器警告您潜在的错误和不需要的副作用。