🪃Gas Saving Tutorial 27: Efficient Boolean Comparison

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Introduction: In smart contract development, every bit of gas saved is crucial, especially for functions that get called frequently. One common micro-optimization that often goes unnoticed is how boolean values are compared. In this tutorial, we'll show you how to make your boolean comparisons more gas-efficient in Solidity.

Concept: Booleans inherently represent true or false. Comparing them directly to true or false is redundant and slightly gas inefficient. Rather than using if (booleanValue == true), you can simply use if (booleanValue). For false checks, instead of if (booleanValue == false), if (!booleanValue) can be used.

Benefits include:

1. Gas Efficiency: Avoiding the direct comparison conserves some gas as fewer opcodes are executed in the EVM.

2. Code Clarity: Directly using the boolean value usually results in more readable and concise code.

Example:

Given the code snippet in a governance system:

solidityCopy codefunction voteOnProposal(uint256 proposalId)
    external
    onlyRegisteredVoter
{
    require(
        hasVoted[msg.sender][proposalId] == false, //@audit gas: instead of comparing to a constant, just use "hasVoted[msg.sender][proposalId]"
        "Voter has already voted on this proposal!"
    );
    ...
}

The optimized boolean comparison would be:

solidityCopy codefunction voteOnProposal(uint256 proposalId)
    external
    onlyRegisteredVoter
{
    require(
        !hasVoted[msg.sender][proposalId], // Simply negate the boolean value for a false check
        "Voter has already voted on this proposal!"
    );
    ...
}

Recommendation:

1. Examine your contracts for boolean comparisons using == true or == false.

2. Replace these direct comparisons with the efficient boolean evaluations.

3. Test to make sure the logic remains consistent and the behavior is as intended.

Conclusion:

Though the savings from boolean comparison optimizations might seem minute, they add up to provide a more gas-efficient and cleaner codebase. In projects with a multitude of such comparisons, the aggregated savings over numerous transactions can be significant. Always aim for efficient, clean code that accomplishes the same objective with fewer operations.