silasjmatson / prime

Session for finding primes

elixir-pdx/prime

---

#Overview

This exercise is designed to be an introduction to both Elixir and the basics of functional programming.

The challenge is to complete the implementation of the Prime.nth_prime function such that when called with a single integer argument it will return to the caller the Nth prime number. For instance, if called as Prime.nth_prime(1000) the result should be 7919. Since the 1000th prime number is 7919.

Prerequisites:

• elixir

---

#Getting Started

There are two different ways to start this project:

###1. Use the mix tool to bootstrap your project.

$ cd ~/Repositories
$ mix new prime
$ cd prime

Then change the contents of lib/prime.ex to match:

defmodule Prime do	

	def nth_prime(1) do
		2
	end

	def nth_prime(number) do
		IO.puts("Called with #{number}")
		number
	end

	defp is_prime(number) do
		false
	end
	
end

and change the contents of test/prime_test.exs to match:

defmodule PrimeTest do
  use ExUnit.Case

  test "nth_prime with 1" do
    assert Prime.nth_prime(1) == 2
  end

  test "nth_prime with 3" do
    assert Prime.nth_prime(3) == 5
  end

  test "nth_prime with 1000" do
    assert Prime.nth_prime(1000) == 7919
  end

end

###2. Clone this repository.

$ cd ~/Repositories
$ git clone https://github.com/elixir-pdx/prime.git
$ cd prime

#Hacking

You may find it helpful to play with your code in Elixir's iex interactive console. If you want to do that and autoload the console session with your code then you can do the following from the project root:

$ iex -S mix

That will make sure that you're running iex inside your project's build environment.

#Building

To compile your project simply run this from the project root:

$ mix compile

#Testing

To run the test suite defined in test/prime_test.exs then run this from the project root:

$ mix test

If you got your project bootstrapped correction you should see something like the following:

lib/prime.ex:12: warning: function is_prime/1 is unused
Compiled lib/prime.ex
Generated prime.app
Called with 3
Called with 1000


  1) test nth_prime with 3 (PrimeTest)
     test/prime_test.exs:8
     Assertion with == failed
     code: Prime.nth_prime(3) == 5
     lhs:  3
     rhs:  5
     stacktrace:
       test/prime_test.exs:9



  2) test nth_prime with 1000 (PrimeTest)
     test/prime_test.exs:12
     Assertion with == failed
     code: Prime.nth_prime(1000) == 7919
     lhs:  1000
     rhs:  7919
     stacktrace:
       test/prime_test.exs:13

.

Finished in 0.05 seconds (0.05s on load, 0.00s on tests)
3 tests, 2 failures