confusion about `unary_op_abs`

functor定义：
```C++
struct unary_op_abs
{
    float operator()(const float& x) const
    {
        return abs(x);
    }
};
```

std::abs原型：
```c++
int       abs( int n );
```

`unary_op_abs`的目的是截断为int类型吗？