Questions tagged [solidity-0.5.x]

Solidity is a contract-oriented, high-level language whose syntax is similar to that of JavaScript and it is designed for writing smart contracts in Ethereum to run on the EVM. Solidity is statically typed, supports inheritance, libraries and complex user-defined types among other features. Solidity version 0.5.0 is a specific version that includes a number of changes to the language and introduce new features.

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The current timestamp is 0x5000. What is the smallest future timestamp that would win the game?

The current timestamp is 0x5000. What is the smallest future timestamp that would win the game?
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Hello there i've problem with Expected primary expression

hello this is my code and error constructor(address _supplyChainAddress) public { supplyChainStorage = SupplyChainStorage(_supplyChainAddress); } and this is an error and i got stuck because ...
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Truffle console: Can't Retrieve Solidity send(..) and transfer(..) from SC code

I have written a program for Truffle console. My code accesses the string and should return statements related to Solidity send and transfer. When I am testing each line of Solidity SC as shown below,...
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BigNumber error

I started learning solidity but when I use construct im getting the error, please help: here's the code pragma solidity >=0.7.0 <0.9.0; contract base{ uint data; constructor (uint ...
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i cant refund my BNB from my contract on remix [duplicate]

my bnb stuck and I cant back it to my wallet! here is the code I used https://ghostbin.com/KgvTS/raw my address https://bscscan.com/address/0xf3321b8f53ed3051fd4f0ae139f04fd6a280c4b7#internaltx
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Converting from Version 4 to Version 5: Problem with Compilation

I got the following Solidity code from: https://www.zupzup.org/smart-contract-interaction/ pragma solidity ^0.5.6; contract Caller { function someAction(address addr) returns(uint) { ...
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Remix's documented test test#2 fails

Why the remix’s documented test#2 fails? Hi, I am following the remix’s example test available at: https://remix-ide.readthedocs.io/en/latest/unittesting_examples.html. The sender code is: pragma ...
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1 vote
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Sending Ether to contracts at object creation: Remix IDE

I am trying to send Ether to 2 Solidity contracts (version 0.5.3) using Remix IDE at the time of object creation. I am using following 2 techniques but getting compilation error: First Method: ...
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TypeError:Exactly one argument expected for explicit type conversion: Should I use 'new' keyword or not?

I have got following contracts: Sender: pragma solidity ^0.5.8; contract sender{ address owner; constructor () public{ owner = msg.sender; } function transferTo(address to, uint amount) public{ ...
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how to test internal variables

I have a contract: contract SS { address payable commissions = payable(0x...02); function doStuff() public payable { (bool success, ) = payable(commissions).call{value: msg.value * 30 / ...
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How to access mapping array and address of contract in truffle test

I have 3 contracts: sender, receiver and transferTest. I am getting error in transferTest due to an address array declared in the reciver contract: receiver.sol: pragma solidity ^0.5.8; contract ...
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Cannot import most libraries out there due to their compiler version being too old

My Contract has pragma solidity ^0.8.0; but I am using this library to be able to split strings that uses pragma solidity ^0.5.0;. Changing this line alone wont fix the issue, it will create new ones (...
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Is the primary reason keccak256(a, b, c) was changed to keccak256(abi.encodePacked(a, b, c)) because of the forgery attack vector?

I am/have been a noob developer attempting to develop dApp. When keccak256(a, b, c) was suddenly deprecated years ago, it seemed to me like it just added unnecessary complexity. In hindsight, I have ...
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Why is array.length giving "length" not found or not visible after argument-dependent lookup in mapping?

Here's how I defined an array of my struct: struct FoodItem { string name; uint price; bool available; } mapping(uint => FoodItem) public foods; Now I want to delete an ...
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1 answer
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How to tell how much money executing something will cost

I understand the difference between transaction costs and execution costs, but I don't understand two things: What does the "gas" readout in Remix refer to? How do I create an estimate of ...
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3 votes
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Include library function without function body

Using solc 0.5.0 it's possible to compile a contract that has a library function implemented with no body. For example: library Hasher { function MiMCSponge(uint256 in_xL, uint256 in_xR) external ...
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Error HH411: The library openzeppelin-solidity is not installed. Try installing it using npm (for old 0.5.0 solidity code)

I have solidity project with files like pragma solidity ^0.5.0; import "openzeppelin-solidity/contracts/ownership/Ownable.sol"; When I try to compile, I get error on not installed library ...
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Compiler version not recognized

Anyone have any ideas how to fix this? Compiler version is there. $ solc --optimize --abi ./contracts/MySmartContract.sol -o build ./contracts/MySmartContract.sol:1:1: Warning: Source file does not ...
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2 votes
1 answer
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What is the logic by which tokens are ordered when creating a new Uniswap V2 pair?

When creating a new pair contract via the UniswapV2Factory contract, the order in which tokens get assigned in storage (that is, the token0 and token1 vars) cannot be arbitrarily set by the caller: (...
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Ethereum DApp with user authentication

I'm creating a healthcare DApp and how can I create user authentication ( For Doctor and Patient). I'm using JavaScript and HTML for most of my UI.
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I can't compile my solidity contract, can someone help correct the code. i've been trying for about 24 hours now

This is my smart contract: pragma solidity ^0.5.0; contract Agent { struct patient { string name; string dob; address[] doctorAccessList; uint[] diagnosis; ...
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call method in compiler 0.8

how can i change this for older compiler versions like 0.4.24? (bool success, ) = transaction.to.call{value: transaction.value}(transaction.data); and if you have time please explain to me the call ...
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1 vote
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Storing constants in Storage vs Creating a view function? (Solidity 0.5.17)

So, which would be gas efficient? Reading a storage variable in a state-changing function? OR Reading from a pure function in a state-changing function? Example: contract Test { uint256 public a = ...
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I need to understand a line of code inside a contract => startTime: _startTime == 0 ? currentTime() : _startTime

I am reading a contract from this location : https://gist.github.com/rstormsf/7cfb0c6b7a835c0c67b4a394b4fd9383 I am not able to understand the logic in the code line 72 startTime: _startTime == 0 ? ...
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Contract pay the rest of gas fee

This is my payable public method1 : //Do sth if (condition) method2(); and as you know, if method2 is called, the user should pay the gas fee for it as well. How can call method2 from inside the ...
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Truffle test is failling with transferFrom.call

When I run tests with the following code, I get the following error: Error Error: Returned error: VM Exception while processing transaction: revert Tests it('Handles delegated token transfers', () =...
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How can a contract accept some ether and send a stablecoin in return

My contract has to take ETH as a collateral and send some stablecoins ( like USDC) to user. How can I use any stablecoin into my contract , assuming contract has an infinite supply of USDC ? I too ...
1 vote
1 answer
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Member "owner" not found or not visible after argument-dependent lookup in type

pragma solidity ^0.5.0; contract reeler{ uint public id; string public name; string public addres; string public state; string public pincode; uint public yarncount = 0; mapping(uint =&...
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how to get array that contain certain value

I'm new in solidity, I want to ask, in my case I want to store a data that may contain the same user ID but different value inside it each transaction, here is my smart contract: pragma solidity 0.5; ...
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Transfer ether in solidity 0.5.16 with truffle

I am currently working with Truffle and Ganache, therefore I use Solidity compiler version 0.5.16. With that version I have some problems to send ethers. I want to transfer ether to a specific address....
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How to ensure that a string parameter to a function is not empty?

Lets say that I have a function which needs two string parameter , function data(string memory _firstname, string memory _lastname) public { buyer[msg.sender] = Buyer(_firstname, _lastname); } Now, I ...
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Gas fee optimization questions [duplicate]

Can some recommend a way to save gas fees? a = a + 1; a++; I heard about this; Pack struct tightly Mine looks like this. I am not sure about size of address, ENUM variables and array without length. ...
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Validation of integers on solidity

I have this function and require the _price variable to be positive, But when I pass a negative int, it accepts the integer! How can I validate the input? The Contract : function createProduct(string ...
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2 answers
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How to I initialise an array inside the contructor in solidity?

I'm using the remix IDE.I want to define the size of the array at the time constructor is called. Someone please help. This is what I tried : pragma solidity >=0.7.0 <0.8.0; contract Vote { ...
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1 answer
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What's wrong with my buyToken function?

Here is my solidity interface IERC20 { function decimals() external view returns (uint8); function totalSupply() external view returns (uint); function balanceOf(address owner) external ...
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require(msg.sender.call("")): No matching declaration found after argument-dependent lookup

I am trying to compile the following Solidity program: pragma solidity ^0.5.9; contract Mutex { bool locked; modifier noReentrancy() { require(!locked); locked = true; ...
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Remix: ParserError: Expected pragma. import directive, or contract/library/interface definition

I'm trying to use Remix to interact with a suite of contracts. One of the contracts being used is OpenZeppelin's Ownable contract. I copied from the link above, and pasted it into Remix, with a few ...
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Issuing 1-1 eth for token problem

pragma solidity 0.6.6; // import "./XYZToken.sol"; contract Vault { mapping(address => uint256) balanceOf; mapping(address => bool) hasDepositedEther; mapping(...
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Transfer funds to inherited smart contracts [closed]

How would I make this work - the balanceOf[Pool, System + Cube] doesn't seem to work ;-; // SPDX-License-Identifier: GPLv2 pragma solidity ^0.7.0; import "./Pool.sol"; import "./Cube....
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1 vote
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Using inherited constructor in Solidity >=0.5.0

I want to use a contract inherit from another contract and use the parent constructor after using another commands in inherited constructor. So I wrote: pragma solidity ^0.5.10; contract A { ...
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How to call the super contract function where msg.sender should be same in solidity?

I am trying to call contract A.fun_A() via Contract C contract A{ function fun_A(address tenant, uint itemId){ //Here the msg.sender should be msg.sender in C require(msg.sender == ...
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Get a blank address

I have a little problem with my code. I'm trying to follow who are the current sender and the previous sender of a transaction respectively with the variable currentSender and lastSender, and then ...
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Getter of mapping inside a struct

I wanted to create a getter function to access a mapping nested inside a struct. But the function that I made required me to use the expiremental version (I'm on Remix). So I used the expiremental ...
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1 answer
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Else if structure gives the wrong output

I have a little problem with a else if struture that doesn't give out the right result. Here is the code: pragma solidity >=0.5.16; contract SupChain{ enum StateType {A, B, C} ...
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Negative integer function

I have the following problem, one of my function has a variable where the uint can be negative but I don't know of that before the user enter in the form the integer. How do I settle this problem ? ...
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Warning! Error encountered during contract execution [execution reverted]

I have an ERC20 Mintable+Burnable Token created on solidity 6.11 and a sale contract on solidity 5.0 I am getting error when i send ETH to the sale contract. https://rinkeby.etherscan.io/tx/...
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Flashloan callFunction being called internally

I had a chance to look at this contract. contract Flashloan is DyDxFlashLoan { uint256 public loan; constructor() public payable { (bool success, ) = WETH.call.value(msg.value)("&...
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Different compiler versions in OpenZepplinn ERC721 folder

We have created a contract by inheriting ERC721Burnable, Ownable contract from openzepplin. The compiler version we are using in our smart contract is 0.6.0. I flattened the smart-contract by using ...
4 votes
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How to get require() error message?

I can see the error message on Etherscan. But I can't find it in getTransactionRecept(). Is there any special settings that I need set in my Genesis.json before I can see it?
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Is it true that we can't make multiple Transfer() to the same address within a single transaction now?

The code below is for illustrative purposes only. Not the actual production code. function payCommission(address[] payee) public payable { for (uint i = 0; i < payee.length; i++) payee[...
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