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November 30, 2019 23:57
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pragma solidity ^0.4.24; | |
/** | |
* @title SafeMath | |
* @dev Math operations with safety checks that throw on error | |
*/ | |
library SafeMath { | |
/** | |
* @dev Multiplies two numbers, throws on overflow. | |
*/ | |
function mul(uint256 a, uint256 b) internal pure returns (uint256) { | |
if (a == 0) { | |
return 0; | |
} | |
uint256 c = a * b; | |
assert(c / a == b); | |
return c; | |
} | |
/** | |
* @dev Integer division of two numbers, truncating the quotient. | |
*/ | |
function div(uint256 a, uint256 b) internal pure returns (uint256) { | |
// assert(b > 0); // Solidity automatically throws when dividing by 0 | |
uint256 c = a / b; | |
// assert(a == b * c + a % b); // There is no case in which this doesn't hold | |
return c; | |
} | |
/** | |
* @dev Substracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend). | |
*/ | |
function sub(uint256 a, uint256 b) internal pure returns (uint256) { | |
assert(b <= a); | |
return a - b; | |
} | |
/** | |
* @dev Adds two numbers, throws on overflow. | |
*/ | |
function add(uint256 a, uint256 b) internal pure returns (uint256) { | |
uint256 c = a + b; | |
assert(c >= a); | |
return c; | |
} | |
} |
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