C#

Dave Kreskowiak wrote:

... values in an enum should not be thought of as variable names at all ... It may work in interpreted languages, but it doesn't work in compiled languages. The variable names no longer exist(*).

Dave Kreskowiak wrote:

context of "beginner"

using System;
using System.Collections.Generic;

namespace YourNameSpace
{
    public enum Fruit
    {
        NoFruit, Apple, Orange
    }

    public class FruitCalc
    {
        private Dictionary<Fruit, Func<int, int, Fruit>> CalcFruitDict
            = new Dictionary<Fruit, Func<int, int, Fruit>>
            {
                // lambda notation used here
                {Fruit.Apple, (int napples, int noranges) => napples > noranges ? Fruit.Apple : Fruit.NoFruit },
                {Fruit.Orange, (int napples, int noranges) => napples < noranges ? Fruit.Orange : Fruit.NoFruit },
            };

        public Fruit Calculate(Fruit fruit, int napples, int noranges)
        {
            if (fruit == Fruit.NoFruit)
            {
                throw new InvalidOperationException("Sorry, no fruit means no fruit");
            }

            // check integer parameters for valid range ?

            return CalcFruitDict[fruit](napples, noranges);
        }
    }
}

FruitCalc fcalc = new FruitCalc();

Fruit f1 = fcalc.Calculate(Fruit.Apple, 12, 4);
Fruit f2 = fcalc.Calculate(Fruit.Orange, 14, 24);

Fruit f3 = fcalc.Calculate(Fruit.Apple, 2, 4);
Fruit f4 = fcalc.Calculate(Fruit.Orange, 14, 2);

// force an error
Fruit f5 = fcalc.Calculate(Fruit.NoFruit, 12, 4);

public Fruit Calculate2(Fruit fruit, int napples, int noranges)
{
    switch (fruit)
    {
        case Fruit.Apple:
            return napples > noranges ? Fruit.Apple : Fruit.NoFruit;
        case Fruit.Orange:
            return napples < noranges ? Fruit.Orange : Fruit.NoFruit;
        default:
            throw new InvalidOperationException("Sorry, no fruit means no fruit");
    }
}

public void DropDownSelectChanged(object sender, EventArgs args)
{
  // assuming the sender is the drop down
  var ddl = sender as DropDown; // whatever the actual control is in your GUI
  Calculate(ddl.SelectedItem);
}

// These get set in your constructor.
public Action MoreApplesAction {get; set;}
public Action FewerApplesAction {get; set;}

public void Caclulate(Fruit selectedFruit)
{
  // Of course, these should be properties somewhere
  var Apple = 5
  var Orange = 1

  // It's OK to create guards like this to
  // enhance readability, but don't be surprised
  // when someone objects because of the memory
  // allocation.
  var MoreApples = Apple > Orange;
  var FewerApples = Apple < Orange;

  switch(selectedFruit)
  {
    case Apple:
      if(MoreApplies) MoreApplesAction?.Invoke();
      break;

    case Orange:
      if(FewerApples) FewerApplesAction?.Invoke();
      break;
  }
}

// required
// using System.Collections.Generic;
// using System.IO;
// using System.Linq;

public class Person
{
    public Person(string name, int age, int telNum, string emailId)
    {
        Name = name;
        Age = age;
        TelNum = telNum;
        EmailId = emailId;
    }

    public string Name { get; set; }
    public int Age { get; set; }
    public int TelNum { get; set; }
    public string EmailId { get; set; }
}

// 2 define a factory that reads a file, and creates a List<Person>

public static class PersonFactory
{

    static char[] delimiter = new []{','};
    
    public static Person MakePerson(string line)
    {
        try
        {
            var data = line.Split(delimiter, StringSplitOptions.RemoveEmptyEntries);
            var name = data[0];
            var age = Int32.Parse(data[1]);
            var tel = Int32.Parse(data[2]);
            var eml = data[3];
    
            return new Person(name, age, tel, eml);
        }
        catch (Exception ex)
        {
            throw new InvalidDataException(ex.Message);
        }
    }
    
    public static List<Person> PersonsFromFile(string filepath)
    {
        // note use of Skip to ignore first line
        // which contains header informatiomn
        var lines = File.ReadAllLines(filepath).Skip(1);
    
        return lines.Select(line => MakePerson(line.Trim())).ToList();
    }
}

var persons = PersonFactory.PersonsFromFile(@"C:\Users\###\##\##?.txt");
            
int chrisage = persons.First(p => p.Name == "Chris").Age;

Member 14571520 wrote:

I am having trouble constructing these matrices..

public class MyData
{
    private System.Globalization.CultureInfo ci = new System.Globalization.CultureInfo("en-US");
    public string Name {get; set;}
    public string Institute {get; set;}
    public int X {get; set;}
    public int Y {get; set;}
    public string[] Headers {get; set;}
    public double[][] DataMatrix {get; set;}
    public MyData(string sFileName)
    {
        if(!File.Exists(sFileName))
            throw new FileNotFoundException($"File '{Path.GetFileName(sFileName)}' does not exist!");

        string[] lines = File.ReadAllLines(sFileName);
        Name = lines[0];
        Institute = lines[1];
        X = Convert.ToInt32(lines[5].Split(' ')[0]);
        Y = Convert.ToInt32(lines[5].Split(' ')[1]);
        Headers = lines[7].Split(new string[]{" : "}, StringSplitOptions.RemoveEmptyEntries);
        DataMatrix = lines.Skip(9)
            .TakeWhile(l=>l.Length>0 && !l.StartsWith("."))
            .Select(l=>l.Split(' ').Select(d=>Double.Parse(d, ci)).ToArray())
            .ToArray();
    }
}

string filename= "C://user//abc.txt";
MyData md = new MyData(filename);
Console.WriteLine(md.Name);
Console.WriteLine(md.Institute);
Console.WriteLine("X = {0}, Y = {1}", md.X, md.Y);
double[] allMasses = md.DataMatrix.Select(m=>m[0]).ToArray();
foreach(double d in allMasses)
    Console.WriteLine(d);
//on the same manner you can get Weight, Time, Velocity, Acceleration and Distance

Member 14571520 wrote:

MandW = new matrix(x,2); /* Mass and Weight Matrix*/

MandW = new double[x,2]; /* Mass and Weight Matrix*/