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.
153
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Call or assignment expected. Getting this error while upgrading solidity version
I am not aware of the Assembly code. I copied the ERC1820 registry contract from here. This is written in 0.5.3. When I tried to compile it with 0.8.0 it gave me this error :
I know it's because of ...
- 53
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1
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24
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how to revert transaction excuted by low level call
Hello ethereum community. I'm experimenting with low level calls and i want to revert the transaction made by low level call, if i didn't get the desired result. Is it possible?
(bool success, ) = ...
- 69
1
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1
answer
28
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Compiler doesn't show a warning if empty function is not marked as pure
When compiling a function without marking its state mutability as pure, the compiler shows the following warning:
Warning: Function state mutability can be restricted to pure
For example:
contract ...
- 536
0
votes
1
answer
207
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Flash Loan Transaction
Please I need help here, I am new to flash loans. I want to understand flash loan transactions on ether scan , how to identify them, if the transaction make profit or not.
I am trying to implement a ...
- 31
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0
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13
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Difference between deployed object and current object?
I have a problem understanding the concept of deployed object. Kindly follow the link:
Executing reentrancy on Truffle Console: attacker not stealing 5 ether , why only 2 reentrant calls?
The link ...
- 1,416
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0
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26
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Truffle Exec Script: VM Exception While Executing (commented line#10) Require
I am trying to execute the following SC:
1.pragma solidity ^0.5.16;
2.contract SSUE2 {
3.address public owner;
4.bool public paused;
5.constructor() public {
6.owner = msg.sender;
...
- 1,416
1
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1
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30
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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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1
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53
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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,...
- 1,416
2
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0
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115
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ParserError: Expected '{' but got reserved keyword 'override' ) external override returns (bool) { ^------^
Can someone fix the code problem below?
I compile in remix.ethereum.org , it show ParserError: Expected ';' but got '}' } external override
The code:
pragma solidity 0.5.8;
/**
Ropsten instances:...
0
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3
answers
686
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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 ...
0
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1
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101
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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
- 1
1
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1
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43
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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) {
...
- 1,416
0
votes
1
answer
65
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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 ...
- 1,416
1
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1
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154
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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:
...
- 1,416
0
votes
1
answer
102
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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 / ...
- 1,145
0
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1
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406
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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 ...
- 1,416
0
votes
2
answers
749
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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 (...
- 167
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votes
1
answer
406
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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 ...
- 103
1
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1
answer
515
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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 ...
- 113
3
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0
answers
181
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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 ...
- 31
3
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4
answers
10k
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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
...
- 551
1
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0
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97
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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 ...
- 125
2
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1
answer
905
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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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0
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1
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139
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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.
0
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1
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396
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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;
...
1
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1
answer
225
views
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 ...
- 41
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1
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211
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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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1
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49
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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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1
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244
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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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0
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259
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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', () =...
0
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0
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456
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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 ...
- 334
2
votes
2
answers
589
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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 =&...
0
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1
answer
220
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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;
...
0
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0
answers
337
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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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1
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2
answers
1k
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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 ...
- 334
0
votes
1
answer
698
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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. ...
- 116
0
votes
0
answers
758
views
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 ...
- 57
1
vote
2
answers
845
views
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
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1
answer
763
views
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 ...
- 195
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1
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532
views
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;
...
- 1,416
0
votes
1
answer
1k
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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 ...
- 2,709
0
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0
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32
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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(...
- 107
0
votes
1
answer
206
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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
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1
answer
1k
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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 {
...
- 505
1
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0
answers
382
views
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 == ...
- 11
0
votes
3
answers
58
views
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 ...
0
votes
1
answer
466
views
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 ...
0
votes
1
answer
41
views
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}
...
- 3
0
votes
0
answers
44
views
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 ?
...
- 3
0
votes
1
answer
1k
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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/...
