forget about loops

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FORGET ABOUT LOOPSDUŠAN KASAN

FORGET ABOUT LOOPSDUŠAN KASAN

github.com/DusanKasan

@DusanKasan

me@dusankasan.com

FORGET ABOUT LOOPSDUŠAN KASAN

What it’ll be about• The problem

• Functional programming

• Collection pipelines

• Collection pipelines in PHP

Problem | FP | Collection Pipelines | PHP

What’s the problem?$output .= "function {$properties['unifunc']} (Smarty_Internal_Template \$_smarty_tpl) {\n"; // include code for pluginsif (!$cache) { if (!empty($_template->compiled->required_plugins[ 'compiled' ])) { foreach ($_template->compiled->required_plugins[ 'compiled' ] as $tmp) { foreach ($tmp as $data) { $file = addslashes($data[ 'file' ]); if (is_array($data[ 'function' ])) { $output .= "if (!is_callable(array('{$data['function'][0]}','{$data['function'][1]}'))) require_once '{$file}';\n"; } else { $output .= "if (!is_callable('{$data['function']}')) require_once '{$file}';\n"; } } } } if ($_template->caching && !empty($_template->compiled->required_plugins[ 'nocache' ])) { $_template->compiled->has_nocache_code = TRUE; $output .= "echo '/*%%SmartyNocache:{$_template->compiled->nocache_hash}%%*/<?php \$_smarty = \$_smarty_tpl->smarty; "; foreach ($_template->compiled->required_plugins[ 'nocache' ] as $tmp) { foreach ($tmp as $data) { $file = addslashes($data[ 'file' ]); if (is_array($data[ 'function' ])) { $output .= addslashes("if (!is_callable(array('{$data['function'][0]}','{$data['function'][1]}'))) require_once '{$file}';\n"); } else { $output .= addslashes("if (!is_callable('{$data['function']}')) require_once '{$file}';\n"); } } } $output .= "?>/*/%%SmartyNocache:{$_template->compiled->nocache_hash}%%*/';\n"; }}

smarty_internal_runtime_codeframe.php

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Let’s boil it down[ { "id": 1, "username": "john", "verified": true, "posts": [ { "body": "Hi I'm John.", "likes": [2, 3, 5] }, { "body": "I hate this site.", "likes": [] } ] }, { "id": 2, "username": "tom", "verified": false, "posts": [] }, { "id": 3, "username": "jane", "verified": true, "posts": [ { "body": "Hi I'm Jane.", "likes": [4, 5] } ] }]

{ "1": [ { "body": "Hi I'm John.", "likes": [2, 3, 5] } ], "3": [ { "body": "Hi I'm jane.", "likes": [4, 5] } ]}

=>

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Let’s boil it down$likedPosts = [];foreach ($users as $user) { if ($user['verified']) { $userId = $user['id']; foreach ($user['posts'] as $post) { if (count($post['likes'])) { $likedPosts[$userId][] = $post; } } }}

4 levels of nesting

Harder to follow / cognitive load

Too much memorization

Refactoring candidate

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Refactoring - extract more functions$likedPosts = [];foreach ($users as $user) { if ($user['verified']) { $userId = $user['id']; foreach ($user['posts'] as $post) { if (count($post['likes'])) { $likedPosts[$userId][] = $post; } } }} private function getLikedPosts(array $posts)

{ $likedPosts = []; foreach ($posts as $post) { if (count($post['likes'])) { $likedPosts[] = $post; } } return $likedPosts; }

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Refactoring - extract more functions$likedPosts = [];foreach ($users as $user) { $likedPosts = $this->getLikedPosts($user['posts']); if ($user['verified'] && count($likedPosts)) { $likedPosts[$user['id']] = $likedPosts; }}

• Pretty good solution

• The new function name carries the meaning of the logic

• Enough for quick understanding

• For real understanding, we’ll hop between functions

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Refactoring - built-in array functions$indexedUsers = [];foreach ($users as $user) { $indexedUsers[$user['id']] = $user; }$verifiedUsers = array_filter( $indexedUsers, function ($user) { return $user['verified']; });

$likedPosts = array_map( function($verifiedUser) { return array_filter( $verifiedUser['posts'], function($post) {return count($post['likes']);} ); }, $verifiedUsers);

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Refactoring - built-in array functions

( °□°) ︵

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Refactoring - built-in array functions$indexedUsers = [];foreach ($users as $user) { $indexedUsers[$user['id']] = $user; }$verifiedUsers = array_filter( $indexedUsers, function ($user) { return $user['verified']; });

$likedPosts = array_map( function($verifiedUser) { return array_filter( $verifiedUser['posts'], function($post) {return count($post['likes']);} ); }, $verifiedUsers);

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Functional programming

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Functional programming buzzwords

Immutability

No side effects

Higher-order functions

Concurrency Parallelism

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Functional programming buzzwords

Immutability function withName(User $user, $name) { $result = User::from($user); $result->setName($name); return $result; } $tim = new User(1, ’tim', ....);$tom = withName($tim, 'tom'); echo $tim->getName(); //'tim'echo $tom->getName(); //'tom'

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

class User{ ... public function withName($name) { return new self($this->getId(), $name, ...); }}

Functional programming buzzwords

Immutability

No side effects

Higher-order functions

Concurrency Parallelism

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Functional programming buzzwords

No side effects $anotherTry = function ($a, $b, $c) { return $a . $b . $c; }; $a = $anotherTry( $randomObscureThing, $_REQUEST['absolutely_safe'], DateTime::ATOM );

$totallyNoSideEffectsHere = function () use ($randomObscureThing) { return $randomObscureThing . $_REQUEST['absolutely_safe'] . DateTime::ATOM; }; $a = $totallyNoSideEffectsHere();

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Functional programming buzzwords

Immutability

No side effects

Higher-order functions

Concurrency Parallelism

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Functional programming buzzwords

Higher-order functions

function show(callable $c) { echo $c();} function style(callable $c) : callable { return function () use ($c) { return '**' . $c() . '**'; };} $nameProvider = function () { return 'John'; }; show($nameProvider); //Johnshow(style($nameProvider)); //**John**

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Functional programming buzzwords

Immutability

No side effects

Higher-order functions

Concurrency Parallelism

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Functional programming buzzwords

Concurrency Parallelism

getOrderDetails( getOrderById($id), getPaymentByOrderId($id) );

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Collection Pipelines ( - )

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Collection Pipelines• What are collections?

• Group of values or key, value pairs

• Think arrays or Traversables

• Collection pipeline

• Design pattern

• Sequential operations on collections

• Operations e.g.: filter, map or reduce

• Used by both FP and OOP languages

• Immutable, lazy, concurrent

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Simple explanation

map([🌽, 🐮, 🐔], cook) => [🍿, 🍔, 🍳]

filter([🍿, 🍔, 🍳], isVegetarian) => [🍿, 🍳]

reduce([🍿, 🍳], eat) => 💩From a tweet by @steveluscher

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Simple explanation

[🌽, 🐮, 🐔]

.map(cook) // [🍿, 🍔, 🍳]

.filter(isVegetarian) // [🍿, 🍳]

.reduce(eat) // 💩

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Collection pipeline operations

append, combine, concat, contains, countBy, cycle, diff, distinct,

drop, dropLast, dropWhile, each, every, except, extract, filter, find,

first, flatten, flip, frequencies, get, getOrDefault, groupBy,

groupByKey, has, indexBy, interleave, interpose, intersect, isEmpty,

isNotEmpty, keys, last, map, mapcat, only, partition, partitionBy,

prepend, realize, reduce, reduceRight, reductions, reject, replace,

reverse, second, shuffle, size, slice, some, sort, splitAt, splitWith,

take, takeNth, takeWhile, transform, toArray, zip,

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

The original problem[ { "id": 1, "username": "john", "verified": true, "posts": [ { "body": "Hi I'm John.", "likes": [2, 3, 5] }, { "body": "I hate this site.", "likes": [] } ] }, { "id": 2, "username": "tom", "verified": false, "posts": [] }, { "id": 3, "username": "jane", "verified": true, "posts": [ { "body": "Hi I'm Jane.", "likes": [4, 5] } ] }]

{ "1": [ { "body": "Hi I'm John.", "likes": [2, 3, 5] } ], "3": [ { "body": "Hi I'm jane.", "likes": [4, 5] } ]}

=>

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Refactoring - Collections$likedPosts = [];foreach ($users as $user) { if ($user['verified']) { $userId = $user['id']; foreach ($user['posts'] as $post) { if (count($post['likes'])) { $likedPosts[$userId][] = $post; } } }}

$likedPosts = Collection::from($users) ->filter(function ($user) {return $user['verified'];}) ->indexBy(function($user) {return $user['id'];}) ->map(function($user) { return Collection::from($user['posts']) ->filter(function($post) {return count($post['likes']);}); }) ->reject(function($posts) {return isEmpty($posts);});

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

When to use collection pipelines• Where you work with collections?

• API

• Import CSV

• Any nontrivial collection based work

• Refactoring of current code base to for comprehension

Drawbacks?• Function call overhead

• You have to understand it :)

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Collection pipelines in PHP• CakePHP Collection (github.com/cakephp/collection)

• Laravel Collections (github.com/illuminate/support)

• PHP-Collection (github.com/emonkak/php-collection)

• Knapsack (github.com/DusanKasan/Knapsack)

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

http://github.com/cakephp/collection
http://github.com/illuminate/support
http://github.com/emonkak/php-collection
http://github.com/DusanKasan/Knapsack

PHP’s shortcomings

$collection->map(function($item) {return $item->field;});

$collection->map($item ~> $item->field);

$collection->map(function($item) { return $item->field; });

$collection->map(function($item) => $item->field);

RFC targeting PHP 7.1

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

Interested?

• Martin Fowler (martinfowler.com)

• Adam Wathan (adamwathan.me/refactoring-to-collections)

• Documentation and tests to the mentioned libraries

FORGET ABOUT LOOPSDUŠAN KASAN Problem | FP | Collection Pipelines | PHP

http://martinfowler.com/
http://adamwathan.me/refactoring-to-collections

FORGET ABOUT LOOPSDUŠAN KASAN

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