im getting this erorr. Operator >= not compatible with types function (address,address) returns (uint256) and uint256.

here is the code for the function with the type eror.

pragma solidity 0.6.3;  

contract zylus {

    mapping (address => uint256) public _balances; 
    uint256 constant private MAX_UINT256 = 2**256 - 1;

    mapping (address => mapping (address => uint256)) public _allowances; 

    string public _name = 'Zylus';
    string public _symbol = 'zyl';
    uint8  public _decimals = 6;
    uint public _totalSupply = 100000000000000000; 

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    function name() public view returns (string memory) {
        return _name; 

    function symbol() public view returns (string memory) {
        return _symbol;
    function decimals() public view returns (uint8) {
        return _decimals; 

    function totalSupply() public view returns (uint256) {
        return _totalSupply;

    function balanceOf(address _owner) public view returns (uint256 balance) {
        return _balances[_owner];

    function transfer(address _to, uint256 _value)payable public returns (bool success) {
        require(_balances[msg.sender] >= _value);
        require(_balances[_to] + _value >= _balances[_to]);
        _balances[msg.sender] -= _value;   
        _balances[_to] += _value;
        emit Transfer(msg.sender, _to, _value);
        return true;                         

    function transferFrom(address _from, address _to, uint256 _value) public view returns (bool success) {
        uint256 allowanc = _allowances[_from][msg.sender];
        require(_balances[_from] >= _value && allowance >= _value);
        _balances[_to] += _value;
        _balances[_from] -= _value;
        if (allowance < MAX_UINT256) {
            _allowances[_from][msg.sender] -= _value;
        emit Transfer(_from, _to, _value); //solhint-disable-line indent, no-unused-vars
        return true;
    function approve(address _spender, uint256 _value) public view returns (bool success) {
        _allowances[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true; // NANDE (why)

    function allowance(address _owner, address _spender) public view returns  (uint256 remaining) {


  • There's a typo on the second line (allowanc -> allowance) but other than that, this compiles fine (when inserting into a token contract). Can you paste the whole of your code? Apr 17, 2021 at 18:29
  • ok here. It wasnt a typo. Its bc it would overwrite another var i made. Apr 17, 2021 at 18:29
  • I editeded the answer for the full code. I tried compiling but it dint work. Apr 17, 2021 at 18:31

2 Answers 2


Two things:

There's a typo on line 51.

uint256 allowanc = _allowances[_from][msg.sender];

...should be:

uint256 allowance = _allowances[_from][msg.sender];

Secondly, the functions transferFrom() and approve() are both modifying state, so they can't be view. Remove view.


Ok. You commented that the assignment uint256 allowanc = _allowances[_from][msg.sender]; was not a typo.

In that case, change require(_balances[_from] >= _value && allowance >= _value); to require(_balances[_from] >= _value && allowanc >= _value);

Also, as @Richard Horrocks said, remove view from the approve and transferFrom functions

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