Stackoverflow.com

If three classes all validate email addresses in the same way, create a shared validation method. That way, if email validation rules change, you update the one method.

Sometimes the simplest solution is to duplicate code in two places rather than build an abstraction. The key is whether the logic is conceptually the same, not just textually similar.

Intent

A one-to-many dependency between object so that when one object (subject) changes, all its dependents (observers) are notified and update automatically.

Inconveniences of Unsigned Types in .NET

Languages like C++ come with convenient support for unsigned integer types where non-negative values make sense. std::size_t is the unsigned integer type of the sizeof and alignof operators. std::size_t is also used when indexing C++ containers.

In contrast, .NET tends to use signed integer types even where unsigned ones would be more intuitive, e.g.,

• List<T>.Count returns an Int32
• Indexing into a List<T> takes in an Int32 index

.NET is language independent. Languages like C#, F#, and Visual Basic target .NET implementations. The Common Language Specification (CLS) is the set of features that are common to all the languages. Of relevance is the fact that Byte, Int16, Int32, and Int64 are the only CLS-compliant integer types.

Parsing

Each line represents a single equation, e.g., 292: 11 6 16 20.

Part One needs to make a decision based on each line independently. Parsing each line into a data structure and yielding that should suffice.

using System.Collections.Immutable;
using System.Text.RegularExpressions;

namespace AoC2024;

public partial class BridgeRepair
{
    public static IEnumerable<CalibrationEquation> Parse(string filePath)
    {
        using var inputReader = new StreamReader(filePath);

        string? line;
        while ((line = inputReader.ReadLine()) != null)
        {
            var numbers = InputLineRegex.Matches(line)
                .Select(match => long.Parse(match.Value));
            yield return new(numbers.First(), numbers.Skip(1).ToImmutableList());
        }
    }

    public readonly record struct CalibrationEquation(
        long Result, ImmutableList<long> Operands);

    private static Regex InputLineRegex = NumbersRegex();

    [GeneratedRegex(@"\d+")]
    static private partial Regex NumbersRegex();
}

Part One

Using only add and multiply, evaluated left-to-right (not according to math precedence rules), determine which equations could possibly be true. For example, \(292 = ((11 + 6) \times 16) + 20\). Of the equations that could possibly be true, what is the sum of their results?

Testing Web Components

While any test framework can work, it’s better to test web components in a browser environment because that’s where they’ll be used. Node-based frameworks would require too much shimming of DOM calls that’d make the tests unrepresentative. and are good options for browser-based testing.

is powered by ES-build, and so is the client-side of the app; let’s go down this path and see where it leads. CommonJS modules don’t work in the browser . Earlier on , using ESM on the server turned out difficult. Hopefully, that doesn’t me bite back now.

Mixins

A mix-in is an abstract subclass. This technique is especially useful in languages where a class can only have a single superclass.

const calculatorMixin = (Base) =>
  class extends Base {
    calc() {}
  };

const randomizerMixin = (Base) =>
  class extends Base {
    randomize() {}
  };

class Foo {}
class Bar extends calculatorMixin(randomizerMixin(Foo)) {}

Syntax Highlighting

Previously, we’d highlight code on the client by loading src/lib/highlight.pack.js, a bundle downloaded from but served from our domain, and then execute hljs.highlightBlock on demand, e.g., on page load, when showing a card, etc. This doesn’t work well with a web-component-centric design. Running hljs.highlightBlock through possible Shadow DOM boundaries is a hassle.

Back in 2018 , we installed highlightjs, a shim for the official HighlightJS. Times have changed and has an official Node package, highlight.js . Now, on the server, compute the syntax-highlighted HTML and have it stored in Card.descriptionHTML. All that’s left is to provide CSS on the client.

How to handle redirects without setting window.location.href?

Right now, there’s a pattern of doing:

sendHTTPRequest("POST", "/login/", {})
  .then((_) => {
      window.location.href = "/";
  })
  .catch((err) => { console.error(err); });

Isn’t this something that the server can do? In response, why not issue a redirect?

A class is a user-defined type provided to represent a concept in the code of a program. Essentially, all language facilities beyond the fundamental types, operators, and statements exist to help define better class or to use them more conveniently.

Day 3 - Advent of Code 2021. Eric Wastl. adventofcode.com . Accessed Feb 23, 2022.

Problem Description

Part One

The submarine has been making some odd creaking noises, so you ask it to produce a diagnostic report just in case.

The diagnostic report (your puzzle input) consists of a list of binary numbers which, when decoded properly, can tell you many useful things about the conditions of the submarine. The first parameter to check is the power consumption.

Problem Statement

\(n!\) means \(n \times (n - 1) \times … \times 3 \times 2 \times 1\).

For example, \(10! = 10 \times 9 \times … \times 3 \times 2 \times 1 = 3628800\), and the sum of the digits in the number \(10!\) is \(3 + 6 + 2 + 8 + 8 + 0 + 0 = 27\).

Find the sum of the digits in the number \(100!\)