Using MetaMask v3.14.1 you can reset your account as follow: Resetting an Account In the Settings menu, MetaMask has a “Reset Account” button. This button wipes the current account’s transaction history, which is used to calculate the current account nonce. Normal users should never have a reason to use this feature. This is useful for … Read more
Yes you can, by using some EVM assembly code to get the address’ code size: function isContract(address addr) returns (bool) { uint size; assembly { size := extcodesize(addr) } return size > 0; }
In solidity every variable is set to 0 by default. You should think of mappings as all possible combinations are set to 0 by default. In your specific case I would use the following: if (buyers[msg.sender].amount == 0)
This is a good question, though not one easily addressed with a simple answer. As @Mat0 commented above, one difference is the approaches that the various platforms are using to achieve consensus. Some use proof of work (PoW), others use variants of byzantine fault tolerant strategies (PBFT, SBFT, etc). Some use PAXOS derivative strategies. Hyperledger … Read more
You should add memory keyword for string parameter, which was introduced in solidity version 0.5.0 As per the documentation: Explicit data location for all variables of struct, array or mapping types is now mandatory. This is also applied to function parameters and return variables. For example, change uint[] x = m_x to uint[] storage x … Read more
On the Web: (Not programmatic, but for completeness…) If you just want to get the balance of an account or contract, you can visit http://etherchain.org or http://etherscan.io. From the geth, eth, pyeth consoles: Using the Javascript API, (which is what the geth, eth and pyeth consoles use), you can get the balance of an account … Read more
Within an Ethereum transaction, the zero-account is just a special case used to indicate that a new contract is being deployed. It is literally ‘0x0’ set to the to field in the raw transaction. Every Ethereum transaction, whether it’s a transfer between two external accounts, a request to execute contract code, or a request to … Read more
Without the memory keyword, Solidity tries to declare variables in storage. Lead Solidity dev chriseth: “You can think of storage as a large array that has a virtual structure… a structure you cannot change at runtime – it is determined by the state variables in your contract”. That is, the structure of storage is set … Read more
Before I answer the main question, I’m going to try to define a bit more precisely what it would mean to write code in Haskell or Idris and compile it to run on an Ethereum-like blockchain. Idris is probably a better fit for this, but I’m going to use Haskell because that’s what I’m familiar … Read more