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function confirmEtherTransaction(txHash, confirmations = 10) {
  setTimeout(async () => {
    
    // Get current number of confirmations and compare it with sought-for value
    const trxConfirmations = await getConfirmations(txHash)
    
    console.log('Transaction with hash ' + txHash + ' has ' + trxConfirmations + ' confirmation(s)')

    if (trxConfirmations >= confirmations) {
      // Handle confirmation event according to your business logic

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function watchTokenTransfers() {
  // Instantiate web3 with WebSocketProvider
  const web3 = new Web3(new Web3.providers.WebsocketProvider('wss://rinkeby.infura.io/ws'))

  // Instantiate token contract object with JSON ABI and address
  const tokenContract = new web3.eth.Contract(
    TOKEN_ABI, process.env.TOKEN_CONTRACT_ADDRESS,
    (error, result) => { if (error) console.log(error) }
  )

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async function getConfirmations(txHash) {
  try {
    // Instantiate web3 with HttpProvider
    const web3 = new Web3('https://rinkeby.infura.io/')

    // Get transaction details
    const trx = await web3.eth.getTransaction(txHash)

    // Get current block number
    const currentBlock = await web3.eth.getBlockNumber()

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function watchEtherTransfers() {
  // Instantiate web3 with WebSocket provider
  const web3 = new Web3(new Web3.providers.WebsocketProvider('wss://rinkeby.infura.io/ws'))

  // Instantiate subscription object
  const subscription = web3.eth.subscribe('pendingTransactions')

  // Subscribe to pending transactions
  subscription.subscribe((error, result) => {
    if (error) console.log(error)

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This gist shows how formal conditions of Solidity smart contracts can be automatically verified even in the presence of potential re-entrant calls from other contracts.

Solidity already supports formal verification of some contracts that do not make calls to other contracts. This of course excludes any contract that transfers Ether or tokens.

The Solidity contract below models a crude crowdfunding contract that can hold Ether and some person can withdraw Ether according to their shares. It is missing the actual access control, but the point that wants to be made

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/**
 * Base contract that all upgradeable contracts should use.
 * 
 * Contracts implementing this interface are all called using delegatecall from
 * a dispatcher. As a result, the _sizes and _dest variables are shared with the
 * dispatcher contract, which allows the called contract to update these at will.
 * 
 * _sizes is a map of function signatures to return value sizes. Due to EVM
 * limitations, these need to be populated by the target contract, so the
 * dispatcher knows how many bytes of data to return from called functions.

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{
    "nonce": "0x0000000000000042",
    "difficulty": "0x40000",
    "alloc": {
            "YOUR_COINBASE_ADDRESS": {
            "balance": "10015200000000000000000"
        }
    },
    "mixhash": "0x0000000000000000000000000000000000000000000000000000000000000000",
    "coinbase": "0x0000000000000000000000000000000000000000",

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use std::rc::Rc;
use std::cell::{RefCell,Ref, RefMut};
use std::ops::Deref;
use std::fmt;

#[derive(Clone)]
struct Shared<T> {
    v: Rc<RefCell<T>>
}

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//
//  debounce-throttle.swift
//
//  Created by Simon Ljungberg on 19/12/16.
//  License: MIT
//

import Foundation

extension TimeInterval {

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@interface NSObject (Debounce)

- (void)debounce:(SEL)action delay:(NSTimeInterval)delay;

@end