从double隐式转换为int？

Question

// Assuming these initializations
int x; 
float y;

这有什么区别：

  x = y = 7.5;

和这个：

  y = x = 7.5;

为什么第一个将y值打印为7.5，第二个将值打印y为7.00？

Answer 1

解释很简单：=从右到左是关联的，这意味着x = y = 7.5;被评估为x = (y = 7.5);与以下相同：

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;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

这些隐式转换可能很不直观。您可能希望提高警告级别，以使编译器警告您潜在的错误和有害的副作用。