1
exercism fetch erlang difference-of-squares

Difference Of Squares

Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.

The square of the sum of the first ten natural numbers is (1 + 2 + ... + 10)² = 55² = 3025.

The sum of the squares of the first ten natural numbers is 1² + 2² + ... + 10² = 385.

Hence the difference between the square of the sum of the first ten natural numbers and the sum of the squares of the first ten natural numbers is 3025 - 385 = 2640.

Running tests

In order to run the tests, issue the following command from the exercise directory:

For running the tests provided, rebar3 is used as it is the official build and dependency management tool for erlang now. Please refer to the tracks installation instructions on how to do that.

In order to run the tests, you can issue the following command from the exercise directory.

1
$ rebar3 eunit

Test versioning

Each problem defines a macro TEST_VERSION in the test file and verifies that the solution defines and exports a function test_version returning that same value.

To make tests pass, add the following to your solution:

1
2
3
4
-export([test_version/0]).

test_version() ->
  1.

The benefit of this is that reviewers can see against which test version an iteration was written if, for example, a previously posted solution does not solve the current problem or passes current tests.

Questions?

For detailed information about the Erlang track, please refer to the help page on the Exercism site. This covers the basic information on setting up the development environment expected by the exercises.

Source

Problem 6 at Project Euler http://projecteuler.net/problem=6

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.