Raindrops 48in24 approaches #1422
Conversation
|
Thank you for contributing to Based on the files changed in this PR, it would be good to pay attention to the following details when reviewing the PR:
Automated comment created by PR Commenter 🤖. |
|
Link checkers will fail until the first deployment, as this PR will create the missing pages. |
| @@ -0,0 +1,49 @@ | |||
| # Introduction | |||
There was a problem hiding this comment.
I think my preference would be to try to start the approaches documents with the "most reasonable" solution first, and explore the more exotic solutions further down. I know that's very subjective, but I hope we can agree on which one is the best 😁
I have a strong opinion for this exercise that the best solution uses a list that pairs divisors to sounds, and then iterates over them like this one:
https://exercism.org/tracks/elixir/exercises/raindrops/solutions/SaberCon
I don't know if you would qualify that as a variant of a "step by step" approach? You didn't mention anything with Enum yet. Maybe it deserves to be its own approach.
Btw. In this exercise it's important to note that maps in Elixir are not sorted. This solution for example https://exercism.org/tracks/elixir/exercises/raindrops/solutions/alkhulaifi has to sort the map first before iterating, which clearly suggests a list of two-tuples is a better data structure here.
| case {rem(number, 3), rem(number, 5), rem(number, 7)} do | ||
| {0, 0, 0} -> "PlingPlangPlong" | ||
| {0, 0, _} -> "PlingPlang" | ||
| {0, _, 0} -> "PlingPlong" | ||
| {_, 0, 0} -> "PlangPlong" | ||
| {0, _, _} -> "Pling" | ||
| {_, 0, _} -> "Plang" | ||
| {_, _, 0} -> "Plong" | ||
| _ -> Integer.to_string(number) | ||
| end |
There was a problem hiding this comment.
I was actually shocked to see this approach, but people actually use it 😮 (found:
https://exercism.org/tracks/elixir/exercises/raindrops/solutions/Martin1982
https://exercism.org/tracks/elixir/exercises/raindrops/solutions/Gorgij
https://exercism.org/tracks/elixir/exercises/raindrops/solutions/NaeosPsy
https://exercism.org/tracks/elixir/exercises/raindrops/solutions/zimakki
)
Can we put it at the bottom of the document?
|
|
||
| All the examples above, at their core, represent the same approach of doing the check step by step. | ||
|
|
||
| [pattern-matching-approach]: https://exercism.org/tracks/elixir/exercises/raindrops/approaches/pattern-matching |
There was a problem hiding this comment.
What's the pattern matching approach for this exercise?
| @@ -0,0 +1,75 @@ | |||
| # Pattern Matching | |||
exercises/practice/raindrops/.approaches/check-every-possibility/content.md
Show resolved
Hide resolved
| # Step By Step | ||
|
|
||
| ```elixir | ||
| defmodule Raindrops do | ||
| @spec convert(pos_integer) :: String.t() | ||
| def convert(number) do | ||
| pling = if rem(number, 3) == 0, do: "Pling", else: "" | ||
| plang = if rem(number, 5) == 0, do: "Plang", else: "" | ||
| plong = if rem(number, 7) == 0, do: "Plong", else: "" | ||
| sound = pling <> plang <> plong | ||
|
|
||
| if sound == "" do | ||
| Integer.to_string(number) | ||
| else | ||
| sound | ||
| end | ||
| end | ||
| end | ||
| ``` | ||
|
|
||
| In this approach, we test each condition only once, similar to using the `case` on a tuple in the [pattern matching approach][pattern-matching-approach]. | ||
| However, this time, if a condition is true, we capture the sound component, and if it is not true, we capture the sound as an empty string. | ||
|
|
||
| Once this is done, we can concatenate all three conditions to get the full sound. | ||
| Finally, if the `sound` is empty, we can return the number or, alternatively, the calculated `sound`. | ||
|
|
||
| ## Functions | ||
|
|
||
| We can create private functions to test for component sounds. | ||
|
|
||
| ```elixir | ||
| defp pling(n) when rem(n, 3) == 0, do: "Pling" | ||
| defp pling(_), do: "" | ||
| defp plang(n) when rem(n, 5) == 0, do: "Plang" | ||
| defp plang(_), do: "" | ||
| defp plong(n) when rem(n, 7) == 0, do: "Plong" | ||
| defp plong(_), do: "" | ||
| defp sound(sound, number) when sound == "", do: Integer.to_string(number) | ||
| defp sound(sound, _number), do: sound | ||
| ``` | ||
|
|
||
| Now the solution can look like this: | ||
| ```elixir | ||
| def convert(number) do | ||
| sound(pling(number) <> plang(number) <> plong(number), number) | ||
| end | ||
| ``` |
There was a problem hiding this comment.
String concatenation isn't used by Elixir devs that often. It has a big disadvantage - it crashes on nils. Elixir devs usually always use string interpolation.
Using string interpolation in both of those solutions would make them slightly shorter:
defmodule Raindrops do
@spec convert(pos_integer) :: String.t()
def convert(number) do
pling = if rem(number, 3) == 0, do: "Pling"
plang = if rem(number, 5) == 0, do: "Plang"
plong = if rem(number, 7) == 0, do: "Plong"
sound = "#{pling}#{plang}#{plong}"
if sound == "" do
Integer.to_string(number)
else
sound
end
end
enddefp pling(n), do: if(rem(n, 3) == 0, do: "Pling")
defp plang(n), do: if(rem(n, 5) == 0, do: "Plang")
defp plong(n), do: if(rem(n, 7) == 0, do: "Plong")
defp sound(sound, number) when sound == "", do: Integer.to_string(number)
defp sound(sound, _number), do: sound
def convert(number) do
sound("#{pling(number)}#{plang(number)}#{plong(number)}", number)
end
Co-authored-by: Angelika Tyborska <[email protected]>
Resolves #1420
I'm trying a different approach to approaches than the one I used in the leap.
Rather than focusing on the features of the language I'm focusing on two logical approaches and showing how they can be implemented differently using various features of the language. Let me know what you think.