SafeMath

SafeMath is a library created by OpenZeppelin to make sure math operations won't cause the overflows.

Example ​

SafeMath attaches 4 functions — add, sub, mul, and div to native data types. We can access them from uint256 as follows:

using SafeMath for uint256;

uint256 a = 5;
uint256 b = a.add(3); // 5 + 3 = 8
uint256 c = a.mul(2); // 5 * 2 = 10

[!tip]

It's a good idea in general to just use SafeMath instead of the basic math operations. Maybe in a future version of Solidity these will be implemented by default, but for now we have to take extra security precautions in our code.

[!danger]

SafeMath library is designed for uint256 type. For uint16/32 you need to implement the library yourself or use an existing implementation (?)