Having trouble returning a true/false boolean value

Question

I am trying to get this method to return a boolean value of true for prime numbers and false for when a number is not prime. So far it is returning true but not false. Here is the code I have created so far.

def prime?(num=1..11)
    array = (1..11).to_a
if num > 1 
    return true 
elsif num / 2 || 3 
    return false 
    end 
end

My logic behind this was that the prime? method would take in a range as an argument and that argument I would set to an array (I have to set it equal to an array in this instance its part of the exercise). Since prime numbers are greater than 1 and divisible by their selves I set it to return true if the range is greater than 1. Since the numbers between 1-11 can be divisible by 2 or 3, I made the method return false if any number is divisible by 2 or 3. I feel I made some error in this code but this is what I am trying to achieve. Thanks for any help!

Answer 1 · 2015-10-05T18:24:52Z

October 5, 2015 6:24pm

Hi ! if you're trying to determine if a number n is prime, why would you pass a range as argument to method prime?() 0 and 1 are not prime (prime number have only two divisers: 1 and themselves) I suggest you this :

def prime?(n)
   if n % 2 == 0 || n % 3 == 0 # if n modulo 2 = 0 or n modulo 3 = 0, n cannot be prime
      return false # not prime
    else
       return true
    end
end

There are 4 particular cases that needs to be adressed : 0 and 1 are not prime 2 and 3 are prime

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Daniel Wise

Daniel Wise

Having trouble returning a true/false boolean value

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samuel gustave

samuel gustave