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What is an easy way to determine if a number is prime?Įxample: Write the number 100 as the sum of two prime numbers.įor me it is difficult to determine whether or not a number is prime. We’ll start with this question from 2008: Checking if a Number from 1-100 is Prime The next question many students have is, how can I make a list of prime numbers (or write a computer program to do so)? We’ll learn about the Sieve of Eratosthenes, and list all the prime numbers up to 1000. Gen_list(10, Z, Z2), Z2=, writeln(Z).We’ve looked at what prime numbers are, and how the concept extends (or doesn’t) to 0, 1, and negative integers. This also enables us to stop and continue the primes generation from the point where we stopped, instead of starting over from the beginning: ?- L =, gen_list(8, L, Z), Z=, writeln(),

Gen_list(X, N, L, Z) :- % get N more odd primes into L's tail

We can introduce a little twist to it, disallowing requests for 0 primes (there's no point to it anyway), so that we also get back the last generated prime: genList(1,, 2) :- !. And you're right, it's essentially a functional programming style. The if-then-else construct embodies the cuts. GenList(X, N, L, Z):- % L-Z is the result: primes list of length N Here's what you meant to write: genList(N, L) :- genList(2, N, L, ). I want to say that when isPrime(X) fails, we continue to the next number without saving anything, but when isPrime(X) is true, then we recurse and continue to the next number, saving X. I definitely feel that this is not logic programming style. This is what I type into the Prolog interpreter: genList(1,N, ,L).įor the 1st line, how do I make the base case such that when N=0, I stop recursing? Is this correct?Īs for the next 2 clauses, I am having difficulty in thinking in terms of logic programming. This is the part of the relevant code: genList(_, 0, _). Generating the prime number is not an issue, but rather, generating it in a list is the issue I have.

I need to generate the first N prime numbers and return it in a list. I believe I am not implementing it right and need help. I have a problem with the recursive function of Prolog.