Initial commit.

.editorconfig

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+# This file is for unifying the coding style for different editors and IDEs
+# editorconfig.org
+
+# PHP PSR-2 Coding Standards
+# http://www.php-fig.org/psr/psr-2/
+
+root = true
+
+[*.{php,inc,module}]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 4
+
+[*.{json,json.dist,yml,yml.dist}]
+indent_size = 4

.gitattributes

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+/spec export-ignore
+.editorconfig export-ignore
+.gitattributes export-ignore
+.gitignore export-ignore
+.scrutinizer.yml export-ignore
+.travis.yml export-ignore
+phpunit.xml.dist export-ignore
+infection.json.dist export-ignore
+grumphp.yml.dist export-ignore
+phpspec.yml.dist export-ignore

.github/CODEOWNERS

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+* @loophp

.github/CODE_OF_CONDUCT.md

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+# Contributor Covenant Code of Conduct
+
+## Our Pledge
+
+In the interest of fostering an open and welcoming environment, we as contributors and maintainers pledge to making participation in our project and our community a harassment-free experience for everyone, regardless of age, body size, disability, ethnicity, gender identity and expression, level of experience, nationality, personal appearance, race, religion, or sexual identity and orientation.
+
+## Our Standards
+
+Examples of behavior that contributes to creating a positive environment include:
+
+* Using welcoming and inclusive language
+* Being respectful of differing viewpoints and experiences
+* Gracefully accepting constructive criticism
+* Focusing on what is best for the community
+* Showing empathy towards other community members
+
+Examples of unacceptable behavior by participants include:
+
+* The use of sexualized language or imagery and unwelcome sexual attention or advances
+* Trolling, insulting/derogatory comments, and personal or political attacks
+* Public or private harassment
+* Publishing others' private information, such as a physical or electronic address, without explicit permission
+* Other conduct which could reasonably be considered inappropriate in a professional setting
+
+## Our Responsibilities
+
+Project maintainers are responsible for clarifying the standards of acceptable behavior and are expected to take appropriate and fair corrective action in response to any instances of unacceptable behavior.
+
+Project maintainers have the right and responsibility to remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned to this Code of Conduct, or to ban temporarily or permanently any contributor for other behaviors that they deem inappropriate, threatening, offensive, or harmful.
+
+## Scope
+
+This Code of Conduct applies both within project spaces and in public spaces when an individual is representing the project or its community. Examples of representing a project or community include using an official project e-mail address, posting via an official social media account, or acting as an appointed representative at an online or offline event. Representation of a project may be further defined and clarified by project maintainers.
+
+## Enforcement
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by contacting the project team at [email protected]. The project team will review and investigate all complaints, and will respond in a way that it deems appropriate to the circumstances. The project team is obligated to maintain confidentiality with regard to the reporter of an incident. Further details of specific enforcement policies may be posted separately.
+
+Project maintainers who do not follow or enforce the Code of Conduct in good faith may face temporary or permanent repercussions as determined by other members of the project's leadership.
+
+## Attribution
+
+This Code of Conduct is adapted from the [Contributor Covenant][homepage], version 1.4, available at [http://contributor-covenant.org/version/1/4][version]
+
+[homepage]: http://contributor-covenant.org
+[version]: http://contributor-covenant.org/version/1/4/

.github/CONTRIBUTING.md

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+# CONTRIBUTING
+
+We're using [Travis CI](https://travis-ci.com) as a continuous integration system.
+
+For details, see [`.travis.yml`](../.travis.yml). 
+
+## Tests
+
+We're using [`grumphp/grumphp`](https://github.com/phpro/grumphp) to drive the development.
+
+Run
+
+```bash
+./vendor/bin/grumphp run
+```
+
+to run all the tests.
+
+## Coding Standards
+
+We are using [`drupol/php-conventions`](https://github.com/drupol/php-conventions) to enforce coding standards.
+
+Run
+
+```bash
+./vendor/bin/grumphp run
+```
+
+to automatically detect/fix coding standard violations.

.github/FUNDING.yml

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+github: loophp

.github/ISSUE_TEMPLATE.md

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+## Steps required to reproduce the problem
+
+1. 
+2. 
+3. 
+
+## Expected Result
+
+* 
+
+## Actual Result
+
+* 

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,9 @@
+This PR
+
+* [x] 
+* [ ] 
+* [ ] 
+
+Follows #.
+Related to #.
+Fixes #.

.github/settings.yml

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+# https://github.com/probot/settings
+
+labels:
+    - name: bug
+      color: ee0701
+
+    - name: dependencies
+      color: 0366d6
+
+    - name: enhancement
+      color: 0e8a16
+
+    - name: question
+      color: cc317c
+
+    - name: security
+      color: ee0701
+
+    - name: stale
+      color: eeeeee
+
+repository:
+    allow_merge_commit: true
+    allow_rebase_merge: false
+    allow_squash_merge: false
+    default_branch: master
+    description: "A curated list of combinators"
+    topics: combinator,combinatory-logic,functional-programming
+    has_downloads: true
+    has_issues: true
+    has_pages: false
+    has_projects: false
+    has_wiki: false
+    name: combinator
+    private: false

.github/stale.yml

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+daysUntilStale: 60
+
+daysUntilClose: 7
+
+staleLabel: stale
+
+markComment: >
+  This issue has been automatically marked as stale because it has not had
+  recent activity. It will be closed if no further activity occurs. Thank you
+  for your contributions.

.github/workflows/continuous-integration.yml

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+# https://help.github.com/en/categories/automating-your-workflow-with-github-actions
+
+on:
+    - pull_request
+    - push
+
+name: "Continuous Integration"
+
+jobs:
+    run:
+        name: "Grumphp"
+        runs-on: ${{ matrix.operating-system }}
+        strategy:
+            fail-fast: false
+            matrix:
+                operating-system: [ubuntu-latest, windows-latest, macOS-latest]
+                php-versions: ['7.1', '7.2', '7.3', '7.4']
+
+        steps:
+            - name: Checkout
+              uses: actions/checkout@master
+              with:
+                  fetch-depth: 1
+
+            - name: Install PHP
+              uses: shivammathur/setup-php@master
+              with:
+                  php-version: ${{ matrix.php-versions }}
+                  extensions: xdebug,mbstring
+
+            - name: Get Composer Cache Directory
+              id: composer-cache
+              run: echo "::set-output name=dir::$(composer config cache-files-dir)"
+
+            - name: Cache dependencies
+              uses: actions/cache@v1
+              with:
+                  path: ${{ steps.composer-cache.outputs.dir }}
+                  key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.json') }}
+                  restore-keys: ${{ runner.os }}-composer-
+
+            - name: Install dependencies
+              run: composer install --no-progress --no-suggest --prefer-dist --optimize-autoloader
+
+            - name: Run Grumphp
+              run: vendor/bin/grumphp run
+              env:
+                  STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}
+
+            - name: Scrutinizer
+              run: vendor/bin/ocular code-coverage:upload --format=php-clover build/logs/clover.xml
+              continue-on-error: true

.gitignore

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+/composer.lock
+/vendor
+/build
+/.php_cs.cache
+/example/
+/.idea/
+/test.php
+/phpspec.yml

.scrutinizer.yml

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+build:
+    nodes:
+        analysis:
+            tests:
+                override:
+                    - php-scrutinizer-run
+
+filter:
+    paths:
+        - 'src/*'
+
+tools:
+    external_code_coverage:
+        timeout: 600
+    php_loc: true
+    php_pdepend: true
+    php_sim: true
+    php_changetracking: true

LICENSE

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+MIT License
+
+Copyright (c) 2018 Pol Dellaiera
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+[![Latest Stable Version](https://img.shields.io/packagist/v/loophp/combinator.svg?style=flat-square)](https://packagist.org/packages/loophp/combinator)
+ [![GitHub stars](https://img.shields.io/github/stars/loophp/combinator.svg?style=flat-square)](https://packagist.org/packages/loophp/combinator)
+ [![Total Downloads](https://img.shields.io/packagist/dt/loophp/combinator.svg?style=flat-square)](https://packagist.org/packages/loophp/combinator)
+ [![GitHub Workflow Status](https://img.shields.io/github/workflow/status/loophp/combinator/Continuous%20Integration?style=flat-square)](https://github.com/loophp/combinator/actions)
+ [![Scrutinizer code quality](https://img.shields.io/scrutinizer/quality/g/loophp/combinator/master.svg?style=flat-square)](https://scrutinizer-ci.com/g/loophp/combinator/?branch=master)
+ [![Code Coverage](https://img.shields.io/scrutinizer/coverage/g/loophp/combinator/master.svg?style=flat-square)](https://scrutinizer-ci.com/g/loophp/combinator/?branch=master)
+ [![Mutation testing badge](https://badge.stryker-mutator.io/github.com/loophp/combinator/master)](https://stryker-mutator.github.io)
+ [![License](https://img.shields.io/packagist/l/loophp/combinator.svg?style=flat-square)](https://packagist.org/packages/loophp/combinator)
+ [![Donate!](https://img.shields.io/badge/Donate-Paypal-brightgreen.svg?style=flat-square)](https://paypal.me/drupol)
+
+# Combinator
+
+This package provides a list of well known Combinators.
+
+A combinator is [a higher-order function](https://en.wikipedia.org/wiki/Higher-order_function) that uses only function
+application and earlier defined combinators to define a result from its arguments.
+It was introduced in 1920 by [Moses Schönfinkel](https://en.wikipedia.org/wiki/Moses_Sch%C3%B6nfinkel) and
+[Haskell Curry](https://en.wikipedia.org/wiki/Haskell_Curry), and has more recently been used in computer
+science as a theoretical model of computation and also as a basis for the design of [functional programming languages](https://en.wikipedia.org/wiki/Functional_programming_languages).
+Combinators which were introduced by Schönfinkel in 1920 with the idea of providing an analogous way to build up
+functions - and to remove any mention of variables - particularly in predicate logic.
+
+## Requirements
+
+* PHP >= 7.1.3
+
+## Installation
+
+```shell script
+composer require loophp/combinator
+```
+
+## Available combinators
+
+| Combinator | Definition                               | # Arguments |
+|------------|------------------------------------------|-------------|
+| A          | `a => b => a(b)`                         | 2           |
+| B          | `a => b => c => a(b(c))`                 | 3           |
+| C          | `a => b => c => a(c)(b)`                 | 3           |
+| D          | `a => b => c => d => a(b)(c(d))`         | 4           |
+| E          | `a => b => c => d => e => a(b)(c(d)(e))` | 5           |
+| F          | `a => b => c => c(b)(a)`                 | 3           |
+| G          | `a => b => c => d => a(d)(b(c))`         | 4           |
+| H          | `a => b => c => a(b)(c)(b)`              | 3           |
+| I          | `a => a`                                 | 1           |
+| J          | `a => b => c => d => a(b)(a(d)(c))`      | 4           |
+| K          | `a => b => a`                            | 2           |
+| L          | `a => b => a(b(b))`                      | 2           |
+| M          | `a => a(a)`                              | 1           |
+| O          | `a => b => b(a(b))`                      | 2           |
+| Psi        | `a => b => c => d => a((b(c))(b(d)))`    | 4           |
+| Q          | `a => b => c => b(a(c))`                 | 3           |
+| R          | `a => b => c => b(c)(a)`                 | 3           |
+| S          | `a => b => c => a(c)(b(c))`              | 3           |
+| T          | `a => b => b(a)`                         | 2           |
+| U          | `a => b => b(a(a)(b))`                   | 2           |
+| V          | `a => b => c => c(a)(b)`                 | 3           |
+| W          | `a => b => a(b)(b)`                      | 2           |
+| Y          | `a => (b => b(b))(b => a(c => b(b)(c)))` | 1           |
+
+Example with the B combinator:
+
+The definition means that the combinator needs 3 arguments: `a`, `b` and `c`.
+The return of this combinator is the result of the function `a` applied to the result of the function `b` applied to `c`.
+
+PHP will first evaluate `b(c)` and will then pass the result to the function `a`, this is what the definition means: `a(b(c))`
+
+## Usage
+
+Example with [the Y combinator](https://en.wikipedia.org/wiki/Fixed-point_combinator).
+
+```php
+<?php
+
+declare(strict_types=1);
+
+include 'vendor/autoload.php';
+
+use loophp\combinator\Y;
+
+$fibonacci = new Y(
+    static function ($f) {
+        return static function ($n) use ($f) {
+            return (1 >= $n) ? $n : ($f($n - 1) + $f($n - 2));
+        };
+    }
+);
+
+$result = $fibonacci()(10);
+```
+
+## Further reading
+
+- [To Mock a Mockingbird](https://en.wikipedia.org/wiki/To_Mock_a_Mockingbird)
+- [http://dkeenan.com/Lambda/](http://dkeenan.com/Lambda/)
+- https://gist.github.com/Avaq/1f0636ec5c8d6aed2e45
+- https://en.wikipedia.org/wiki/Combinatory_logic
+- https://github.com/sanctuary-js/sanctuary
+- https://en.wikipedia.org/wiki/Lambda_calculus
+
+## Authors
+
+* Pol Dellaiera