ðŸŽ‰ Exercism Research is now launched. Help Exercism, help science and have some fun at research.exercism.io ðŸŽ‰

# filipeherculano's solution

## to Series in the Elixir Track

Published at Jul 11 2020 · 0 comments
Instructions
Test suite
Solution

Given a string of digits, output all the contiguous substrings of length `n` in that string in the order that they appear.

For example, the string "49142" has the following 3-digit series:

• "491"
• "914"
• "142"

And the following 4-digit series:

• "4914"
• "9142"

And if you ask for a 6-digit series from a 5-digit string, you deserve whatever you get.

Note that these series are only required to occupy adjacent positions in the input; the digits need not be numerically consecutive.

## Running tests

Execute the tests with:

``````\$ mix test
``````

### Pending tests

In the test suites, all but the first test have been skipped.

Once you get a test passing, you can unskip the next one by commenting out the relevant `@tag :pending` with a `#` symbol.

For example:

``````# @tag :pending
test "shouting" do
assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
end
``````

Or, you can enable all the tests by commenting out the `ExUnit.configure` line in the test suite.

``````# ExUnit.configure exclude: :pending, trace: true
``````

If you're stuck on something, it may help to look at some of the available resources out there where answers might be found.

## Source

A subset of the Problem 8 at Project Euler http://projecteuler.net/problem=8

## Submitting Incomplete Solutions

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

### series_test.exs

``````defmodule StringSeriesTest do
use ExUnit.Case

# @tag :pending
test "slices of size 1" do
assert StringSeries.slices("01234", 1) == ["0", "1", "2", "3", "4"]
end

@tag :pending
test "slices of size 2" do
assert StringSeries.slices("01234", 2) == ["01", "12", "23", "34"]
end

@tag :pending
test "slices of size 3" do
assert StringSeries.slices("01234", 3) == ["012", "123", "234"]
end

@tag :pending
test "slices of size 4" do
assert StringSeries.slices("01234", 4) == ["0123", "1234"]
end

@tag :pending
test "slices same size as string" do
assert StringSeries.slices("01234", 5) == ["01234"]
end

@tag :pending
test "Unicode characters count as a single character" do
assert StringSeries.slices("JosÃ©", 1) == ["J", "o", "s", "Ã©"]
assert StringSeries.slices("JosÃ©", 2) == ["Jo", "os", "sÃ©"]
end

@tag :pending
test "slices with size longer than string return empty list" do
assert StringSeries.slices("01234", 6) == []
end

@tag :pending
test "slices with size zero or negative return empty list" do
assert StringSeries.slices("01234", -1) == []
assert StringSeries.slices("01234", 0) == []
end
end``````

### test_helper.exs

``````ExUnit.start()
ExUnit.configure(exclude: :pending, trace: true)``````
``````defmodule StringSeries do
@doc """
Given a string `s` and a positive integer `size`, return all substrings
of that size. If `size` is greater than the length of `s`, or less than 1,
return an empty list.
"""
@spec slices(s :: String.t(), size :: integer) :: list(String.t())
def slices(s, size) when size > 0 do
s
|> to_charlist()
|> Enum.chunk_every(size, 1, :discard)
|> Enum.map(&to_string/1)
end

def slices(_, _), do: []
end``````

### What can you learn from this solution?

A huge amount can be learned from reading other peopleâ€™s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

• What compromises have been made?
• Are there new concepts here that you could read more about to improve your understanding?