Implement new Concept Exercise: `with`

[angelikatyborska]

Getting started

Please please please read the docs before starting. Posting PRs without reading these docs will be a lot more frustrating for you during the review cycle, and exhaust Exercism's maintainers' time. So, before diving into the implementation, please read up on the following documents:

• The features of v3.
• Rationale for v3.
• What are concept exercise and how they are structured?

Goal

The goal of this exercise is to teach the student how the with special form works and when it is appropriate to use (e.g. to avoid nested cases)

Learning objectives

• Know how to use with to chain matching clauses
• Know how to use the else block in with to match on different kinds of errors
• Know when not to use with

Out of scope

?

Concepts

• with

Prerequisites

• errors (the with special form is most commonly used with error/ok-tuples and the exercise should teach that)
• pattern-matching
• other, depending on the story

Exercises

Maybe sgf-parsing could have with in its requirements?

Resources to refer to

• https://hexdocs.pm/elixir/Kernel.SpecialForms.html#with/1
• https://elixir-lang.org/getting-started/mix-otp/docs-tests-and-with.html#with
• http://learningelixir.joekain.com/learning-elixir-with/
• https://openmymind.net/Elixirs-With-Statement/

Analyzer

It will be necessary to use the analyzer to check that the with form was indeed used, and that no alternatives (e.g. cases) were used.

Help

If you have any questions while implementing the exercise, please post the questions as comments in this issue.

[ThiagosLima]

Hi, I am still learning Elixir and want to help with some issues in the future. But for now, I have just a comment.

This Analyzer part that assure students use the correct function could be added in some exercises. Like Strain exercise which it is not supposed to use filter and reject. And the Accumulate exercise that it is note supposed to use collect, map or fmap.

I don't know if it is already done in the v3. By the way, nice work with the Elixir track. It is really good!

[neenjaw]

@ThiagosLima thanks for the comment!! Glad to have you here! Yes, that is the eventual goal to add this functionality to practice exercises at some point too. :)

If you want to open an issue in our analyzer repo. Would help us to keep track of that: https://github.com/exercism/elixir-analyzer

[ThiagosLima]

Thanks! @neenjaw that is nice! I didn't know about the analyzer repo haha! Sorry. I will add the issues for the exercises that I saw.