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# Backup
docker exec CONTAINER /usr/bin/mysqldump -u root --password=root DATABASE > backup.sql

# Restore
cat backup.sql | docker exec -i CONTAINER /usr/bin/mysql -u root --password=root DATABASE

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class ActiveRecord::Base
  def can_destroy?
    self.class.reflect_on_all_associations.all? do |assoc|
      assoc.options[:dependent] != :restrict || (assoc.macro == :has_one && self.send(assoc.name).nil?) || (assoc.macro == :has_many && self.send(assoc.name).empty?)
    end
  end
end

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Falsehoods that Ethereum programmers believe

I recently stumbled upon Falsehoods programmers believe about time zones, which got a good laugh out of me. It reminded me of other great lists of falsehoods, such as about names or time, and made me look for an equivalent for Ethereum. Having found none, here is my humble contribution to this set.

About Gas

Calling estimateGas will return the gas required by my transaction

Calling estimateGas will return the gas that your transaction would require if it were mined now. The current state of the chain may be very different to the state in which your tx will get mined. So when your tx i

spalladino

var request = require('request');
var express = require('express');
var http = require('http');
var url = require('url');

// Parse command line options
var program = require('commander');

program
    .version("1.0.0")

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Estructuras de datos probabilísticas

• No devuelven la respuesta exacta, sino una estimación.
• En algoritmos de streaming, suele ser mejor una respuesta aproximada en el momento a una exacta mucho más tarde

Set membership

• Estructura Bloom filter para set membership, usa tiempo constante para add y query
• Hashing (tomar un fingerprint de todos los datos) suele ser mejor técnica que sampling (leer solamente algunos datos al azar), ya que genera solo falsos positivos, no negativos

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#!/usr/bin/env node

if (process.env.NODE_ENV === 'production') {
  throw new Error("Do not use nodemon in production, run bin/www.js directly instead");
}

const nodemon = require('nodemon');
const ngrok = require('ngrok');

// We start an ngrok tunnel to ensure it stays the same for the entire process

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pragma solidity ^0.7.0;

// Each mining pool that intends to provide flash loans deploys a Loaner contract and transfers ETH to it
// When testing each bundle, the diff in balance in this contract is taking into account for calculating effective gas price
// The contract loans funds only on blocks mined by the miner and on zero-gasprice txs
contract Loaner {
    address immutable owner;
    
    constructor(address _owner) {
        owner = _owner;

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class Graph:
    
    def __init__(self, n):
        self.n = n
        self.adjs = []
        self.edges = set()
        for i in range(n):
            self.adjs.append(set())
        
    def add_edge(self, v, w):

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// Adapted from https://github.com/MetaMask/faq/blob/master/DEVELOPERS.md#partly_sunny-web3---ethereum-browser-environment-check
window.addEventListener('load', function() {

  // Checking if Web3 has been injected by the browser (Mist/MetaMask)
  if (typeof web3 !== 'undefined') {
    // Use Mist/MetaMask's provider
    window.web3 = new Web3(web3.currentProvider);
  } else {
    // fallback - use your fallback strategy (local node / hosted node + in-dapp id mgmt / fail)
    window.web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));

spalladino

testruby.bundle: testruby.cr
	crystal testruby.cr --link-flags "-dynamic -bundle -Wl,-undefined,dynamic_lookup" -o testruby.bundle

irb: testruby.bundle
	irb -rtestruby -I.

clean:
	rm -rf .crystal testruby.bundle