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Error: Truffle is currently using solc 0.5.8,

i run migrate in the terminalbut it shows Error: Truffle is currently using solc 0.5.8, but one or more of your contracts specify "pragma solidity ^0.4.27". Please update your truffle config or ...
0
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1answer
14 views

What is the meaning of “memory is erased between (external) function calls”?

From the official documentation on the memory keyword: The second is “memory”, this is used to hold temporary values. It is erased between (external) function calls and is cheaper to use. Can ...
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0answers
14 views

Undefined Contract

I am finally able to come up with a compilable code. As I attempt to verify the contract, the Remix - Ethereum output is "undefined". Someone advice me on what to do. My ABI is as follows: [ { "...
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0answers
11 views

Contract address is not shown in rinkeby testnet etherscan

I am using Getch with truffle framework and i created an account. I have Migrations and Election.sol. After i can migrate, i couldnt see it in etherscan website. Although truffle migrate --reset --...
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0answers
8 views

ICO fund withdrawal

we are a launch platform ICO Projects, we create tokens and smart contracts on behalf of the project owners. we raise fund on behalf of them and once ICO fund softcap / end date reached, can we ...
-1
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1answer
10 views

Check the math on a crypto project

Here is my whitepaper for my project https://cracknet.io/docs/wp0.pdf Wrote it by myself is the mathematics correct?
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0answers
6 views

Is centralized data with a token to reward participation with the content a tried and true business model?

Are there any apps that do this? Would the token gain more value if the data was decentralized?
0
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1answer
11 views

Is it safe to share my signed transaction publicly?

If someone got hold of my Ethereum signed transaction, is my wallet still safe? Can they extract the raw transaction from the signed transaction to get my private key?
0
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1answer
9 views

How can i `ecrecover` in solidity to verify the digest produced by `web3.utils.soliditySha3` in JS side?

Javascript side: id = 128 uri = "xxx://xxx" hash = web3.utils.soliditySha3(id,uri) sign = web3.eth.accounts.sign(hash1, privateKey) Solidity side: function(uint256 id, string memory uri,bytes v, ...
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2answers
34 views

How to reduce the gas price for complicated smart contracts?

This is my smart contract's calculateReward function: function calculateReward(uint256 _amount, address _sender) internal view returns (uint256) { uint256 reward = 0; for (uint256 i= ...
-1
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0answers
15 views

__callback was called after the specified delay

My smart contract should return the ETH rate from Coinbase api .. So i'm using Provable engine and i'm testing my smart contract locally using ganache and ethereum-bridge . It's expected that result ...
0
votes
1answer
18 views

web3 on react-native : Error: Returned error: insufficient funds for gas * price + value

using web3@1.0.0-beta.33 and react-native@0.59.10, because latest web3 have install issue on react-native, after deep research 1.0.0-beta.33 is suitable on react-native const web3 = new Web3("https://...
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1answer
10 views

Trying to build a coin - ParserError: Expected '(' but got identifier constructor KoandCo( [on hold]

I have this error message browser/KoandCo.sol:20:17: ParserError: Expected '(' but got identifier constructor KoandCo( ^-----^ And my code is: constructor KoandCo( uint256 ...
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0answers
16 views

How do you activate an else statement after a web3.js call is thrown?

General purpose of code: I am trying to create a helper function that returns true if an element exists in a dynamic array in solidity, and false if an element does not exist at a certain index ...
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0answers
13 views

subscription to “pendingTransactions” stop after 5 or 6 hours runing

i have the next code: function subscribsEth(){ var subscription = web3.eth.subscribe('pendingTransactions', function(error, result){ if(!error){ web3.eth.getTransaction(result,function(...
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0answers
9 views

Cannot install web3 on nodejs

When I try to install web3 using 'npm install ethereum/web3.js --save' command, I get the following error messages- npm ERR! path git npm ERR! code ENOENT npm ERR! errno ENOENT npm ERR! syscall spawn ...
1
vote
1answer
30 views

Is the gast cost of '<=' lower than the gas cost of '<'?

I've been debating on whether I should use < or <= in a for loop. So I decided to conduct a small test and verify that their gas costs are the same. Here is my contract: pragma solidity 0.4....
1
vote
1answer
23 views

Missing create2 opcode in ethereum yellow paper

In eip 1014 Vitalik added Create2 at opcode 0xf5 Adds a new opcode at 0xf5 But in ethereum yellow paper opcode i don't see opcode 0xf5 or any create2 opcode, it doesn't appear in https://www....
0
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1answer
16 views

I am getting the following wrror while i tried to do node <file name> and also truffle test <file name>

Error: Cannot find module 'web3' at Function.Module._resolveFilename (internal/modules/cjs/loader.js:581:15) at Function.Module._load (internal/modules/cjs/loader.js:507:25) at Module....
0
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1answer
29 views

Empty array is being returned

Am trying to add few hashes into an array and retrieve those but the getHash() is returning an empty array. My smart contract is : pragma solidity ^0.5.0; contract simpleexample{ bytes32 public ...
0
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1answer
38 views

Gas required exceeds allowance truffle migrate

Hi i am trying to work truffle migrate and firstly it start to Migration.sol and then Election.sol. When start to deploy ELection.sol it throws following error. What should i write gas:270000 instead ...
0
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1answer
23 views

Why Should I use Ethereum in an Online-Election(Vote) System based on ZKP(Zero-Knowledge Proof)?

I am an undergraduate student studying Ethereum in South Korea. Currently, I am developing an online election system that can be applied. At first, I came up with this idea: The system has an ETC ...
0
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1answer
20 views

How can I freeze an erc20 token in another holder's wallet

Token was compromised and some portions went to a wrong hand, now owners of token wants to freeze that wallet holding it, is there any way to do this.
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0answers
19 views

ERC20 is not working after deploy

I've deployed an ERC20 like this: const fs = require("fs"); const Web3 = require('web3'); const testnet = 'http://localhost:8545'; const PrivateKeyProvider = require("truffle-privatekey-provider"); ...
1
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0answers
9 views

Genesis Block mismatch with seemingly exact same file

I run a private Eth network with geth. I have two nodes on the network. I had these nodes connected over the last months. However, today when I try to connect one to the other I get an error: err="...
0
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0answers
13 views

How to detect ERC20 token amount sent in the incoming transaction?

Using python's web3 is there some method to detect how many tokens were sent? I.e. detect how many ERC20 USDT tokens were sent to my account address?
0
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0answers
18 views

Error while installing truffle-hdwallet-provider

I am on windows OS and my current python version is 3.6 and node version is v10.12.0 I am trying to install truffle-hdwallet-provider by running following command: npm install --save truffle-...
0
votes
1answer
21 views

How to remove 2 contracts

I have 2 contracts to be removed 0xc4ba2bbfc1d35d4a6dc37d7764081a1880e5a281 unable to verify source for some reason. 0xf3db7f7f6419bf537fd24eb530b6eace38850c0c contains 0 tokens. How do i do this? ...
1
vote
0answers
20 views

Is there an API to Download source code of verified smart contracts from etherscan?

There is same question on stackexchange but the answer to that question does not include the new api on etherscan which, given an address as input, allows you to download source code of that verified ...
0
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0answers
13 views

How can I update the web3.js of Geth? [duplicate]

Web3.js has so many newer versions than one of Geth. I want to use the 1.2.0 version (or newer) web3 with Geth. When compiling, can I replace the old version with any newer version?
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2answers
22 views

ParserError: Expected identifier, got 'LParen' constructor() public {

i don't know why i get this problem, anybody who can helps thanks a lot pragma solidity ^0.4.21; contract MathContract { function mulAtoB(uint a, uint b) pure public returns(uint) { ...
0
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1answer
21 views

After POS is implemented, what stops mining pools from being formed?

There won't be "mining pools" but stake pools but what if someone creates a system where participants stake everthing in one place in order to make the mkst money? Is this allowed and is this a ...
1
vote
2answers
27 views

invalid bytes32 value - Maker Contract Call

I am trying to call the Maker CDP Contract manager smart contract. I want to get the information from this public mapping in the contract. mapping (bytes32 => Cup) public cups and should ...
0
votes
1answer
11 views

Is allocating a portion of tokens to the dapp creator after a crowdsale a bad business move? [on hold]

Will this lessen the integrity of the dapp? Will people trust the company less?
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0answers
29 views

Sending ether to a list of accounts in a loop but only the first account receives ether

I'm implementing a betting smart contracts where users can stake on games and if their team won then admin pay all of the winners by calling function payoutWinners() but the problem is when I call the ...
0
votes
1answer
12 views

Is a Raspberry Pi 2 a suitable piece of hardware to run a Quorum Node with Tessera? If so has it been done?

I would like to set up some Quorum nodes (5) for test purposes and thus far have been unsuccessful in getting a node to run on a Pi 2. The work has stopped due to the need to recompile the binaries ...
1
vote
1answer
27 views

Can I deploy smart contract written in an older version of solidity ? If yes how to recognize it in EVM?

If I can compile a smart-contract written in an older version say 0.1.3, can I still deploy it? If I can, is there a way to look at EVM bytecode and tell that this smart contract is written with an ...
0
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0answers
32 views

web3.js version is 1.2.1 , Error: Returned values aren't valid, did it run Out of Gas?

my web3.js version is 1.2.1 let testAddr = "0x0c1A5F4556B09C89D29c1F4C4b2497EEd81aF31D"; let contract = new web3.eth.Contract(abi, contractAddress, {gasPrice: '3000000', from: userAddr}); ...
0
votes
1answer
31 views

getPastEvents cannot handle multiple requests?

When I send about 100-120 requests in async, it is fine, the event will give me a response. But above 150 or so, I get "Invalid JSON RPC response: "" Web3JS 1.2.1 Geth Info: Version: 1.8.12-stable ...
0
votes
2answers
19 views

Rinkeby not producing blocks

transactions are not getting mined on rinkeby testnet and last block time is almost 2 hours ago. How did such things happen in a decentralised network?
0
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0answers
41 views

How to get the result from another contract's Optional method while return empty if it does not exist or throws? [duplicate]

For example I want to write a contract where when one passes the address of another contract to it, it will check whether this other contract has the name() function, and if the name() function ...
0
votes
1answer
23 views

Can someone explain to me how to add USDT support to my wallet? I use my own GETH node

How to listen USDT contract? How to transfer my USDT to another USDT wallet? How to use both ETH and USDT in the same service? Etc. As you can see, I am new to these issues and would be grateful for ...
0
votes
0answers
12 views

DAO that automatically renews its own Ethereum Name Service with ether generated from its Dapp?

Are you allowed/is it possible to create a DAO that automatically renews its own Ethereum Name system domain with ether collected from a dapp? Are we allowed to do this or does it have to be a human ...
2
votes
1answer
34 views

Different outputs for Keccak256(), which one is right?

To get a value from contract storage I used this geth code succesfully: var contractAddress = '0x88e726de6cbadc47159c6ccd4f7868ae7a037730' var index = '...
0
votes
1answer
14 views

Get array of structs by giving address as parameter

Here's my code: contract company { struct contractDetails { string contractId; string companyA; string companyB; address A; address B; uint256 ...
0
votes
1answer
12 views

How the consensus informations are transported across the network?

Lets consider the scenario, if one node in India, finds the nonce (in pow) and it will generate the block and propagate to the network. How the block will move across the each and every node of the ...
0
votes
1answer
24 views

Is Ethereum suitable as a store of value?

Say you bought some ether when ethereum was at 1.0. Most of the time Ethereum requires you to update (via a hard fork) to the latest software. This means you'd need to update your wallet every time ...
-1
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0answers
21 views

Geth - deploy smart contract in a private blockchain [on hold]

storage.get.call() returns 0 Always for any integer value What may be the solution?
1
vote
2answers
28 views

Is Metamask (and other tools like it) a threat to decentralization? [on hold]

The concept of cryptocurrencies were to remove trust but tools like metamask require you to trust them with your front end.
0
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2answers
30 views

How to cancel pending transaction of ethereum from exchange wallet? [duplicate]

How to cancel pending transaction of ethereum from exchange wallet? It is pending for around 36 hours now. There is no available tx hash.

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