Function goldbach

other/primelib.py:267–312

Goldbach's assumption input: a even positive integer 'number' > 2 returns a list of two prime numbers whose sum is equal to 'number'

(number)

    
    
def goldbach(number):
    """
        Goldbach's assumption
        input: a even positive integer 'number' > 2
        returns a list of two prime numbers whose sum is equal to 'number'
    """
    
    # precondition
    assert isinstance(number,int) and (number > 2) and isEven(number), \
    "'number' must been an int, even and > 2"
    
    ans = [] # this list will returned
    
    # creates a list of prime numbers between 2 up to 'number'
    primeNumbers = getPrimeNumbers(number)
    lenPN = len(primeNumbers)    

    # run variable for while-loops.
    i = 0
    j = 1
    
    # exit variable. for break up the loops
    loop = True
    
    while (i < lenPN and loop):
        
        j = i+1
        
        
        while (j < lenPN and loop):
            
            if primeNumbers[i] + primeNumbers[j] == number:
                loop = False
                ans.append(primeNumbers[i])
                ans.append(primeNumbers[j])
                
            j += 1

        i += 1
        
    # precondition
    assert isinstance(ans,list) and (len(ans) == 2) and \
    (ans[0] + ans[1] == number) and isPrime(ans[0]) and isPrime(ans[1]), \
    "'ans' must contains two primes. And sum of elements must been eq 'number'"
        
    return ans
    
# ----------------------------------------------