uint256 private constant MAX = ~uint256(0);
uint256 private constant _tTotal = 10 * 10**6 * 10**9;
uint256 private _rTotal = (MAX - (MAX % _tTotal));
What is the value of the MAX and _rTotal constants?
I couldn’t understand the MAX constant 
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Hi, ～ means bitwise negation, so ~uint256(0) = 2**256-1, that is the max value in the type of uint256, and these are just some mathematical calculations, if you do not know, you can deploy the contract to see the final result:
uint256 public constant MAX = ~uint256(0);
uint256 public constant _tTotal = 10 * 10**6 * 10**9;
uint256 public _rTotal = (MAX - (MAX % _tTotal));
So the results are:
MAX = 115792089237316195423570985008687907853269984665640564039457584007913129639935
_tTotal = 10000000000000000
_rTotal = 115792089237316195423570985008687907853269984665640564039457580000000000000000
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Where can I check the value of these constants while writing the contract?
for example:
console.log(MAX)
print(MAX)
echo(MAX)
What should I do if I want to see the result as defined as?
I am still in the first hours so I am very inexperienced 
what should be in a developer’s bag? Which tools and what are their functions?
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You can use console.log, https://medium.com/nomic-labs-blog/better-solidity-debugging-console-log-is-finally-here-fc66c54f2c4a, but now, this plugin renamed hardhat
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thank you so much. Let’s see how the result will be
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