[v3] Implement new Concept Exercise: `Higher-order functions`

Start by reading docs/features-of-v3.md, docs/rationale-for-v3.md, and docs/concept-exercises.md, then review the JavaScript elyses-transformative-enchantments exercise and the linked Clojure guide. Create the specified .docs, .meta, source, and test files under languages/clojure/exercises/concept/; done means the exercise teaches the listed higher-order-function objectives and its tests and metadata follow the v3 structure.

This issue describes how to implement the Higher-order functions concept exercise for the Clojure track.

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?

Please also watch the following video:

• The Anatomy of a Concept Exercise.

Goal

The goal of this exercise is to teach the student how to use higher-order functions in Clojure.

It can be a simple port of elyses-transformative-enchantments from the JavaScript Track.

Learning objectives

The student will gain a general understanding of:

• First Class Functions
• Functions that take one or more functions as arguments
• Functions that return a function as its result

Out of scope

• This is a general overview of the concept, not in-depth usage of specific functions.

Concepts

• higher-order-functions

Prerequisites

• basics

Resources to refer to

Clojure guide - Higher Order Functions

Representer

The Clojure Representer is currently being implemented and contributions are welcome.

Analyzer

The Clojure Analyzer is currently being implemented and contributions are welcome.

Implementing

To implement a concept exercise, the following files must be created:

languages
└── clojure
    └── exercises
        └── concept
            └── <SLUG>
                ├── .docs
                |   ├── instructions.md
                |   ├── introduction.md
                |   ├── hints.md
                |   └── after.md (optional)
                ├── .meta
                |   |── design.md
                |   └── Example.clj
                ├── <NAME>.clj
                └── <NAME>_test.clj

Help

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