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My ultimate goal is to have an array of token, e.g. mapping (address => x) token_balance; where x is of type a float/double. As far as I'm aware, Solidity does not support float/double values. …

I've read somewhere says storing values in logs is cheaper than storing it in the contract's permanent storage. I wondered if it is the case. If yes, why? More general question: What is the pros and …

My question is related to my previous question: Solidity: How can a contract B, burn from contract A, generate another contract? As we can in the aforementioned post when we are deploying contract …

Please let me know to delete the question if it's already been asked. I was told (by a colleague of mine) that adding more external function to a smart contract increases its gas. I tested (on rem …

Im learning Solidity. As far as I'm aware, it's recommended using "require" to handle errors. But, I'd like to inform the users about the kind of errors they make, e.g. an argument is invalid or out o …

I'm aware that Solidity doesn't support double and floating values. I'd like to know if there's any way, in Solidity, to get the floor of a division, like: floor(x/2), where x can be any arbitrary "u …

Assume we have a variable in a smart contract. When it reaches a certain value (as a result of interacting with), it posts an advert on social media, like Facebook, and pays for it. Question: Is it …

I have a smart contract that has only one payable function and one that pays, as follows: contract DAO_Test{ // define something function buyToken() payable external returns(bool){ uin …

As we know, in every function call we can add {from: "address, value:5, gass: 420000}. I wondered who provides these capabilities? Is it Solidity, VM or web3.

As we know, in order for a contract to call the other contract, it needs to know the called contract interface/abstract. Question 1: Can we pass that interface/abstract as a function argument to a c …

Assume I have a contract A: pragma solidity ^0.4.4; contract A{ struct St{ uint val; } function double(uint a)external returns (uint res){ res= 2*a; } } Let's call the above lines of …

I wondered if "transfer()" function is a call or a transaction. We know contracts only send messages, not transactions. If a DAO-like contract has a variable and a threshold when the variable reac …

As we know msg.value in contract is in wei. I wondered if there is a better way to convert it to Ether than dividing it by 10^18? As an application consider the case where people buy tokens and the c …

In a smart contract, if we make a member variable public: Question 1: Can a malicious party write a transaction/contract and change the value/state of the public variable in the contract? Question 2: …

I'm trying to design a user interface for private blockchain using Ethereum to test my contracts. So, users with different password and account address login. I'm aware of this question, but it was …