OLD higher-order functions concept exercise

[BethanyG]

This issue describes how to implement the higher-order functions concept exercise for the python 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:

• Contributing to Exercism | Exercism and GitHub | Contributor Pull Request Guide
• What are those Weird Task Tags about?
• Building Language Tracks: An Overview
• What are Concepts?
• Concept Exercise Specifications
• Concept Specifications
• Exercism Formatting and Style Guide
• Exercism Markdown Specification
• Reputation

Goal

This concept exercise is meant to teach a deeper understanding/use of higher-order functions in python.

Learning objectives

• Understand and create higher-order functions in Python
• Create functions used as arguments to other functions
• Create functions that return functions
• Learn about currying
• Understand and create closures -- where an inner function has access to a variable from it's enclosing scope (the outer function) that has completed its execution.
• Understand and use simple recursion-- where a function calls itself as an argument.

Out of scope

• comprehensions
• decorators (these will have their own exercise)
• functools (this will get its own exercise)
• functools.wraps
• generators
• lambda, anonymous functions
• map(), filter(), and reduce() (these will get their own exercise)

Concepts

• closures
• currying
• functions, higher-order functions
• functions as arguments
• functions as returns
• recursion

Prerequisites

These are the concepts/concept exercises the student needs to complete/understand before solving this concept exercise.

• basics
• booleans
• comparisons
• dicts
• dict-methods
• functions
• function-arguments
• argument unpacking
• iteration
• lists
• list-methods
• numbers
• sequences
• sets
• strings
• string-methods
• tuples

Resources to refer to

• Python Docs: Python Scopes and Namespaces
• Python Docs: Defining Functions
• Dan Bader: Python s Functions are First-Class
• Functions as Objects in Python
• Composing Programs: Higher-Order Functions
• Tobias Kohn: Closures in Python
• zetcode: Python Closures
• Sagnick: Python is the Haskell you Never Knew You Had: Currying
• Oreilly: Associating Parameters with a Function (Currying)
• Real Python: Thinking Recursively in Python
• Train Your Brain to Think Recursively

• Hints

  For more information on writing hints see hints

  • You can refer to one or more of the resources linked above, or analogous resources from a trusted source. We prefer using links within the Python Docs as the primary go-to, but other resources listed above are also good. Please try to avoid paid or subscription-based links if possible.

• links.json

  For more information, see concept links file

  • The same resources listed in this issue can be used as a starting point for the concepts/links.json file, if it doesn't already exist.
  • If there are particularly good/interesting information sources for this concept that extend or supplement the concept exercise material & the resources already listed -- please add them to the links.json document.

Concept Description

Please see the following for more details on these files: concepts & concept exercises

• Concept about.md

  Concept file/issue: There is currently no issue or files for the concept. They are TBD.

  For more information, see Concept about.md

  • This file provides information about this concept for a student who has completed the corresponding concept exercise. It is intended as a reference for continued learning.

• Concept introduction.md

  For more information, see Concept introduction.md

  • This can also be a summary/paraphrase of the document listed above, and will provide a brief introduction of the concept for a student who has not yet completed the concept exercise. It should contain a good summation of the concept, but not go into lots of detail.

• Exercise introduction.md

  For more information, see Exercise introduction.md

  • This should also summarize/paraphrase the above document, but with enough information and examples for the student to complete the tasks outlined in this concept exercise.

Test-runner

No changes required to the Python Test Runner at this time.

Representer

No changes required to the Python Representer at this time.

Analyzer

No changes required to the Python Analyzer at this time.

Exercise Metadata - Track

For more information on concept exercises and formatting for the Python track config.json , please see concept exercise metadata. The track config.json file can be found in the root of the Python repo.

You can use the below for the exercise UUID. You can also generate a new one via exercism configlet, uuidgenerator.net, or any other favorite method. The UUID must be a valid V4 UUID.

• Exercise UUID : 37e7b0bd-6d70-415f-806b-cda91173c7c8
• concepts should be filled in from the Concepts section in this issue
• prerequisites should be filled in from the Prerequisites section in this issue

Exercise Metadata Files Under .meta/config.json

For more information on exercise .meta/ files and formatting, see concept exercise metadata files

• .meta/config.json - see this link for the fields and formatting of this file.
• .meta/design.md - see this link for the formatting of this file. Please use the Goal, Learning Objectives,Concepts, Prerequisites and , Out of Scope sections from this issue.

Implementation Notes

• Code in the .meta/examplar.py file should only use syntax & concepts introduced in this exercise or one of its prerequisite exercises.
• Please do not use comprehensions, generator expressions, or other syntax not previously covered. Please also follow PEP8 guidelines.
• In General, tests should be written using unittest.TestCase and the test file should be named <EXERCISE-NAME>_test.py.
• While we do use PyTest as our test runner and for some implementation tests, please check with a maintainer before using a PyTest test method, fixture, or feature.
• Our markdown and JSON files are checked against prettier . We recommend setting prettier up locally and running it prior to submitting your PR to avoid any CI errors.

Help

If you have any questions while implementing the exercise, please post the questions as comments in this issue, or contact one of the maintainers on our Slack channel.

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