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organize chapters for the ongoing research, remove dead links, add new resources

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bt3gl 2024-11-04 18:42:30 +07:00
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advanced_expert/vulnerabilities/arithmetic_errors/overflow.md
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## overflow of numbers
<br>
<br>
----
### unchecked math
<br>
* overflow and underflow of numbers in solidity 0.8 throw an error. this can be disabled with `unchecked`.
* disabling overflow / underflow check saves gas.
<br>
```
contract UncheckedMath {
function add(uint x, uint y) external pure returns (uint) {
// 22291 gas
// return x + y;
// 22103 gas
unchecked {
return x + y;
}
}
function sub(uint x, uint y) external pure returns (uint) {
// 22329 gas
// return x - y;
// 22147 gas
unchecked {
return x - y;
}
}
function sumOfCubes(uint x, uint y) external pure returns (uint) {
// Wrap complex math logic inside unchecked
unchecked {
uint x3 = x * x * x;
uint y3 = y * y * y;
return x3 + y3;
}
}
}
```
<br>