👂Gas Saving Technique 30: Using 1 and 2 rather than 0 and 1 saves gas

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Introduction: Solidity is a unique language with many nuances that can affect gas consumption. One such nuance involves the representation and usage of integer constants. This tutorial will dive into why using 1 and 2 as constant values can be more gas-efficient than 0 and 1.

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Concept: In Ethereum, the EVM (Ethereum Virtual Machine) treats the integer value 0 differently, as it's the default value of storage slots. When a storage slot is set to 0, the EVM refunds some gas because it assumes that you're freeing up storage. However, if you're using 0 and 1 for flagging or other logical purposes and not for freeing storage, this gas refund is not beneficial. Moreover, setting a value to 1 costs slightly more than setting it to any other non-zero value. Therefore, using 1 and 2 (or any other pair of non-zero values) can be more gas-efficient.

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Underlying Problem:

1. Unnecessary Gas Refund: Using 0 as a logical constant can trigger gas refunds, which are counterproductive if the intention isn't to free up storage.

2. Higher Cost for 1: Setting a value to 1 in storage is slightly more expensive than setting it to other non-zero values.

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Examples & Recommendations:

1. DepositHandler Constants:

   • Before:

     solidityCopy codeuint256 internal constant IS_NOT_LOCKED = uint256(0);
     uint256 internal constant IS_LOCKED = uint256(1);

   • After:

     solidityCopy codeuint256 internal constant IS_NOT_LOCKED = uint256(1);
     uint256 internal constant IS_LOCKED = uint256(2);

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Step-by-Step Guide to Implementing the Integer Gas Saving Technique:

1. Review your contract for instances where 0 and 1 are used as logical constants or flags.

2. Change those constants to 1 and 2 respectively.

3. Ensure that any conditional checks or logic that relied on these constants are updated accordingly.

4. Test the modified contract thoroughly to ensure consistent functionality.

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Benefits:

1. Gas Savings: By avoiding the default storage value (0) and the slightly higher cost of 1, contracts can conserve gas over multiple transactions.

2. Clearer Intention: Using 1 and 2 makes it clear that these values are being used for logic, not for storage clearing.

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Conclusion: Solidity, with its ties to the Ethereum ecosystem, has many peculiarities that can influence gas costs. Understanding these intricacies, like the special treatment of integer values 0 and 1, allows developers to write more optimized and efficient contracts.