该代码如何工作，它叫什么

Question

The code in question is "? something : something_else". Usually in the code below you can put either I2C_SLAVE or I2C_SLAVE_FORCE. But this code does something else. How does it work and what exactly does it do?

if(ioctl(state.i2c_bus_address, force ? I2C_SLAVE_FORCE : I2C_SLAVE, add) < 0)
{
    logger.fail("i2c select fail %d",add);
    return -1;
}

Answer 1

It's called the ternary conditional operator. It's like an if, but inline. Here's the format

boolean ? result evaluated to if true : result evaluated to if false

Here's an example:

y = x>2 ? 12 : 5;

If x is greater than 2, y will be 12, otherwise y will be 5.

Answer 2

It's name is "conditional operator".

condition ? expression1 : expression2

If condition evaluates to true, then evaluate expression1 , otherwise evaluate expression2 .

Answer 3

Not sure if this is what you're after, but the statement ? if_true : if_false statement ? if_true : if_false control flow is called the ternary operator.

The statement is evaluated. If it's true, the expression after the : is evaluated. Otherwise, the expression after the : is evaluated.