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Tech deep dive: Interest Bearing {asset} token

An interest Bearing collateralised, streamable token earning yield via all Strategies involved in the Liquidity Direction Protocol of Alluo.
The Interest Bearing {asset} token is developed and used by Alluo to run deposit farms.
Currently, there are 4 Interest Bearing tokens on Polygon and Ethereum: IbAlluoUSD, IbAlluoEUR, IbAlluoBTC and IbAlluoETH.

How is it interest-bearing?

We have a value growingRatio that increases overtime at the interestPerSecondrate that is set biweekly by the DAO through governance votes. This growingRatio is routinely called by a gelato resolver and updateRatio() is also called before any movement of IbAlluo to ensure that users get the correct values
IbAlluo.sol
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/// @notice Updates the growingRatio
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/// @dev If more than the updateTimeLimit has passed, call changeRatio from interestHelper to get correct index
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/// Then update the index and set the lastInterestCompound date.
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function updateRatio() public whenNotPaused {
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if (block.timestamp >= lastInterestCompound + updateTimeLimit) {
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growingRatio = changeRatio(
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growingRatio,
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interestPerSecond,
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lastInterestCompound
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);
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lastInterestCompound = block.timestamp;
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}
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}
An example can be seen below, where if a user wants to transfer exactly $100 USD worth of IbAlluoUSD (keep in mind that 100 IbAlluoUSD is worth 100 * growingRatio > 1 ), the function ensures that the ratio is up to date when transferring $100 worth.
IbAlluo.sol
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/**
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* @dev See {IERC20-transfer} but it transfers amount of tokens
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* which represents asset value
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*/
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function transferAssetValue(address to, uint256 amount)
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public
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whenNotPaused
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returns (bool)
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{
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address owner = _msgSender();
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updateRatio();
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uint256 adjustedAmount = (amount * multiplier) / growingRatio;
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_transfer(owner, to, adjustedAmount);
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emit TransferAssetValue(owner, to, adjustedAmount, amount, growingRatio);
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return true;
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}
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Key functionality:

The next few subpages will touch upon some key functionalities in the IbAlluo contract, including: