http://www.cplusplus.com/
round() Returns the integral value that is nearest to x, with halfway cases rounded away from zero
floor() Rounds x downward, returning the largest integral value that is not greater than x
ceil() Rounds x upward, returning the smallest integral value that is not less than x
trunc() The nearest integral value that is not larger in magnitude than x (as a floating-point value)
| value | round | floor | ceil | trunc |
|---|---|---|---|---|
| 2.3 | 2.0 | 2.0 | 3.0 | 2.0 |
| 3.8 | 4.0 | 3.0 | 4.0 | 3.0 |
| 5.5 | 6.0 | 5.0 | 6.0 | 5.0 |
| -2.3 | -2.0 | -3.0 | -2.0 | -2.0 |
| -3.8 | -4.0 | -4.0 | -3.0 | -3.0 |
| -5.5 | -6.0 | -6.0 | -5.0 | -5.0 |