ExampleQRC20.sol

// SPDX-License-Identifier: BUSL-1.1
pragma solidity ^0.8.20;

/// @title ExampleQRC20
/// @notice A minimal QRC20 fungible token for the Quantova Virtual Machine (QVM).
/// @dev QRC20 mirrors the familiar fungible-token surface (balances, transfers,
///      approvals) for the QVM. The QVM is Solidity-compatible, so this compiles
///      with a standard Solidity toolchain and deploys as a QVM transaction
///      (see scripts/deploy.js and docs/deploying.md).
///
///      This example keeps the core surface only. A production QRC20 may add the
///      optional post-quantum permit (a gasless approval authorized by a Falcon
///      signature and verified on-chain via the Falcon precompile, with a
///      monotonic per-account nonce for replay protection). See the QRC20
///      standard in the developer documentation.
contract ExampleQRC20 {
    string public name;
    string public symbol;
    uint8 public constant decimals = 18;
    uint256 public totalSupply;

    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

    /// @param _name   Token name.
    /// @param _symbol Token symbol.
    /// @param _initialSupply Initial supply (in whole tokens; scaled by 10**decimals).
    constructor(string memory _name, string memory _symbol, uint256 _initialSupply) {
        name = _name;
        symbol = _symbol;
        uint256 minted = _initialSupply * (10 ** decimals);
        totalSupply = minted;
        balanceOf[msg.sender] = minted;
        emit Transfer(address(0), msg.sender, minted);
    }

    function transfer(address to, uint256 value) external returns (bool) {
        _transfer(msg.sender, to, value);
        return true;
    }

    function approve(address spender, uint256 value) external returns (bool) {
        allowance[msg.sender][spender] = value;
        emit Approval(msg.sender, spender, value);
        return true;
    }

    function transferFrom(address from, address to, uint256 value) external returns (bool) {
        uint256 allowed = allowance[from][msg.sender];
        require(allowed >= value, "QRC20: insufficient allowance");
        if (allowed != type(uint256).max) {
            allowance[from][msg.sender] = allowed - value;
        }
        _transfer(from, to, value);
        return true;
    }

    function _transfer(address from, address to, uint256 value) internal {
        require(to != address(0), "QRC20: transfer to zero address");
        uint256 bal = balanceOf[from];
        require(bal >= value, "QRC20: insufficient balance");
        unchecked {
            balanceOf[from] = bal - value;
            balanceOf[to] += value;
        }
        emit Transfer(from, to, value);
    }
}