Loops and gas in Solidity

Every pass costs gas; bounded arrays keep loops honest.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

// Loops cost gas per pass, so bounded arrays keep them honest.
contract WeighStation {
    uint256[] public cratesKg;

    function log(uint256 kg) external {
        cratesKg.push(kg);
    }

    function total() external view returns (uint256 sum) {
        uint256 n = cratesKg.length;
        for (uint256 i = 0; i < n; i++) {
            sum += cratesKg[i];  // named return accumulates
        }
    }

    function heaviest() external view returns (uint256 best) {
        for (uint256 i = 0; i < cratesKg.length; i++) {
            if (cratesKg[i] > best) best = cratesKg[i];
        }
    }
}

How it works

1. Caching length before the loop saves repeated reads.
2. A named return like uint256 sum accumulates directly.
3. Unbounded growth makes total() costlier every push.

Keywords and builtins used here

• contract
• external
• for
• function
• if
• public
• returns
• uint256

The run, in numbers

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24

Characters to type

560

Tokens

126

Three-star pace

60 tpm

At the three-star pace of 60 tokens a minute, this run takes about 126 seconds.

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Step 2 of 3 in Data & gas, step 15 of 28 in Language basics.

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