Variable length arrays in C#

Question

I have a class which defines few global variables as below:

namespace Algo
{
    public static class AlgorithmParameters
    {
        public int pop_size = 100;

    }
}

In my another csharp file, which also contains the main(), and in the main() I am declaring an array of type structure and the array size as pop_size but I am getting some error on "chromo_typ Population[AlgorithmParameters.pop_size];". Please find the code below. Am I using a incorrect syntax for array declaration of variable length size??

namespace Algo
{
    class Program
    {
        struct chromo_typ
        {
            string   bits;  
            float    fitness;

            chromo_typ() {
                bits = "";
                fitness = 0.0f;
            }

            chromo_typ(string bts, float ftns)
            {
                bits = bts;
                fitness = ftns;
            }
        };

        static void Main(string[] args)
        {

            while (true)
            {
                chromo_typ Population[AlgorithmParameters.pop_size];
            }
        }
    }
}

Error is:

Bad array declarator: To declare a managed array the rank specifier precedes the variable's identifier. To declare a fixed size buffer field, use the fixed keyword before the field type.

Array size cannot be specified in a variable declaration (try initializing with a 'new' expression)

Please help.

Guffa · Accepted Answer · 2012-04-21 23:04:04Z

12

You don't specify the size when you declare the variable, you specify it when you create the instance of the array:

chromo_typ[] Population = new chromo_typ[AlgorithmParameters.pop_size];

Or if you separate the declaration and creation:

chromo_typ[] Population;
Population = new chromo_typ[AlgorithmParameters.pop_size];

answered Apr 21, 2012 at 23:04

Guffa

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3 Comments

user1277070 Over a year ago

An object reference is required for the non-static field, method, or property 'Algo.AlgorithmParameters.pop_size'

Douglas Over a year ago

You need to make pop_size static, eg, public static int pop_size = 100;

user1277070 Over a year ago

ohh ok I changed pop_size to static int... Thanks

Steve · Accepted Answer · 2012-04-21 23:13:08Z

2

Change the initialize in this way:

        //while (true) ///??? what is the reason for this infinite loop ???
        //{ 
            chromo_typ[] Population = new chrom_typ[AlgorithmParameters.pop_size] ; 
        //}

also you need to change pop_size to a static because is declared inside a static class.

edited Apr 21, 2012 at 23:13

answered Apr 21, 2012 at 23:05

Steve

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Comments

ninja · Accepted Answer · 2012-04-21 23:16:17Z

1

Not sure why you have to use a while(true)

But in any case, to declare array, you have to do this:

chromo_typ[] Population = new chromo_typ[AlgorithmParameters.pop_size];

and also you have to declare the member pop_size as static in AlgorithmParameters

public static class AlgorithmParameters
{
     public static int pop_size = 100;
}

answered Apr 21, 2012 at 23:16

ninja

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1 Comment

ninja Over a year ago

One more thing, struct cannot have a default constructor.

Suraj Rao · Accepted Answer · 2022-12-18 04:29:19Z

0

Try to change the initialization statement as below, it will create an instance

chromo_typ[] Population = new chrom_typ[AlgorithmParameters.pop_size] ;

edited Dec 18, 2022 at 4:29

Suraj Rao

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answered Dec 18, 2022 at 4:28

Monukumar S

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