C#•2y ago

✅ This shouldn't work for 2 and 3 but it does

Prime number checker:

static void Plus(int number)
        {
            Func<int, int> addone = x => (number + 1) / 6;
            Func<int, int> minusone = y => (number - 1) / 6;

            if (addone(number) % 6 != 0 || minusone(number) % 6 != 0)
            {
                Console.WriteLine("{0} is not prime", number);
            }
            else
            {
                Console.WriteLine("{0} is prime", number);
            }
        }

static void Plus(int number)
        {
            Func<int, int> addone = x => (number + 1) / 6;
            Func<int, int> minusone = y => (number - 1) / 6;

            if (addone(number) % 6 != 0 || minusone(number) % 6 != 0)
            {
                Console.WriteLine("{0} is not prime", number);
            }
            else
            {
                Console.WriteLine("{0} is prime", number);
            }
        }

29 Replies

Buddy•2y ago

$details

MODiX•2y ago

When you ask a question, make sure you include as much detail as possible. Such as code, the issue you are facing, and what you expect the result to be. Upload code here https://paste.mod.gg/ (see $code for more information on how to paste your code)

Kouhai•2y ago

Why do your delegates take parameters, you're discarding them.

DanyalOP•2y ago

By delegates do you mean the Funcs?

Kouhai•2y ago

Yeah

DanyalOP•2y ago

It told me to write it like that online

Kouhai•2y ago

Who told you to write it like that? You can basically think of this code like this

int number = 10
addone(20); 
int addone(int x)
{
  return (number + 1) / 6
}

int number = 10
addone(20); 
int addone(int x)
{
  return (number + 1) / 6
}

You're not using the parameter x

DanyalOP•2y ago

Kouhai•2y ago

Now to answer why it fails it's because (3+1/6) = 0 0 % 6 = 0 Yeah, here the parameter is used

DanyalOP•2y ago

I'm new to lambda that's why my code is bad

Matt•2y ago

why are you using delegates anyways

DanyalOP•2y ago

because my teacher wanted us to impress him and we hadnt learnt about them

Kouhai•2y ago

Well, using lambdas and delegates doesn't make sense tbh It's redundant

DanyalOP•2y ago

so its not needed?

Kouhai•2y ago

Yeah, it's not

DanyalOP•2y ago

oh so when would it be needed?

Kouhai•2y ago

Lambdas or delegates?

Matt•2y ago

I don't think this is a valid prime number checker? Number 17 is prime but that code says it isn't unless I'm missing something lol.

Kouhai•2y ago

Yeah, it won't work, it'll fail on 4 for example

DanyalOP•2y ago

lambdas

Matt•2y ago

(17 + 1) / 6 = 3 which doesn't divide by 6 exactly

DanyalOP•2y ago

yeah

Kouhai•2y ago

you can think of lambdas as basically inline functions

Matt•2y ago

assuming you're doing an Uni course, your teacher most likely wants you to implement a primality test like the ones at https://en.wikipedia.org/wiki/Primality_test

DanyalOP•2y ago

im in college

Kouhai•2y ago

They are called "closures", they can access variables in the the outside scope. In your example, you can see how you access the number parameters x => (number + 1) / 6;

DanyalOP•2y ago

yeah

Kouhai•2y ago

In your case, you don't need to do that at all

DanyalOP•2y ago

alright thanks for the help!

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✅ This shouldn't work for 2 and 3 but it does