（CS0266、CS0120）我可以通过查看列表的实例来避免被要求访问我的列表吗？

Question

I'm having trouble compiling this program because of the errors noted in the title. My aim is for this program to output the zeros of a quadratic function.

I tried using.ElementAt(at line 14) to rectify the issue but I am apparently attempting to implement it improperly. I don't understand why I can't access my List (line 25).

using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
    int quad(List<double> terms) //takes input from terms list and outputs a list of doubles
    {
        double discriminant = Math.Sqrt(terms[1] * terms[1] - 4 * terms[0] * terms[2]);
        double quad1 = (-terms[1] + discriminant) / 2 * terms[0];
        double quad2 = (-terms[1] - discriminant) / 2 * terms[0];
        double[] quadOutput = new double[] { quad1, quad2 };
        foreach (var term in terms)
        {
            Console.WriteLine(quadOutput[term]); 
        }
        return 0;
    }



    static void Main(string[] args)
    {
        Console.WriteLine("Please enter terms (a,b,c)");
        var userInput = Console.ReadLine();
        List<double> terms = userInput.Split(',') //static?
                             .Select(Convert.ToDouble)
                             .ToList();
        quad(terms);
    }
}

I'm using mcs to compile on linux(arch64)

Error Codes:

CS0266: Cannot implicitly convert type double' to int'. An explicit conversion exists (are you missing a cast?)

CS0120: An object reference is required to access non-static member `Program.quad(System.Collections.Generic.List)'

Edit: Fixed both original problems but now i think the conversion from double to int (for the index) is rounding up somehow? Program compiles but upon running(given input) it gives multiple index out of bounds errors.

using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
    int quad(List<double> terms) //takes input from terms list and outputs a list of doubles
    {
        double discriminant = Math.Sqrt(terms[1] * terms[1] - 4 * terms[0] * terms[2]);
        double quad1 = (-terms[1] + discriminant) / 2 * terms[0];
        double quad2 = (-terms[1] - discriminant) / 2 * terms[0];
        double[] quadOutput = new double[] { quad1, quad2 };
        foreach (var term in terms)
        {
            Console.WriteLine(quadOutput[(Convert.ToInt32(term))]); //how is this converting double to int?
        }
        return 0;
    }



    static void Main(string[] args)
    {
        Console.WriteLine("Please enter terms (a,b,c)");
        var userInput = Console.ReadLine();
        List<double> terms = userInput.Split(',') 
                             .Select(Convert.ToDouble)
                             .ToList();
        Program q = new Program();
        q.quad(terms);
    }
}

Answer 1

using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
    int quad(List<double> terms) //takes input from terms list and outputs a list of doubles
    {
        double discriminant = Math.Sqrt(terms[1] * terms[1] - 4 * terms[0] * terms[2]);
        double quad1 = (-terms[1] + discriminant) / 2 * terms[0];
        double quad2 = (-terms[1] - discriminant) / 2 * terms[0];
        double[] quadOutput = new double[] { quad1, quad2 };
        foreach (var output in quadOutput) //works as expected
        {
            Console.WriteLine(output);
        }
        return 0;
    }



    static void Main(string[] args)
    {
        Console.WriteLine("Please enter terms (a,b,c)");
        var userInput = Console.ReadLine();
        List<double> terms = userInput.Split(',') 
                             .Select(Convert.ToDouble)
                             .ToList();
        Program q = new Program();
        q.quad(terms);
    }
}

Sorry for the confusion, I was for some reason trying to use the terms List to index. I guess I'm tired. Program now works as intended.

Answer 2

quadOutput is an array of doubles terms is a list of doubles

you're trying to say "give me quadOutput at index of (double)"

that's why it's invalid. you wouldn't be able to say quadOutput[1.3] because you can't get an index of 1.3 of an array

either turn your terms to a list of ints or cast your 'term' to an int