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TURN ON THE GENERATOR

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ARRAYS $coordinates = [ [039.842286, -108.457031], [032.916485, -113.906250], [033.431441, -099.404297], [042.032974, -097.031250], [050.064192, -106.962891], ]; foreach ($coordinates as $coordinate) { CDC::innoculate($coordinate); } print "innoculate " . count($coordinates) . " places"; $filter = function($coordinate) { return $coordinate[1] < -98; }; $breakouts = array_filter($coordinates, $filter);

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THINGS LIKE ARRAYS $secret = new DomDocument(); $secret->loadHTMLFile( "secure/2021/lockdown-protocols.html" ); $steps = $secret->getElementsByTagName("h1"); foreach ($steps as $step) { Military::follow($step); } print "followed " . $steps->length . " steps";

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THINGS LIKE ARRAYS is_array($coordinates) // 㱺 true is_array($steps) // 㱺 false $coordinates instanceof Traversable // 㱺 error $steps instanceof Traversable // 㱺 true

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THINGS LIKE ARRAYS class ContainmentProtocols implements Traversable { } // 㱺 error

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ITERATORS class EvacuationProcedures implements Iterator { function current(); function key(); function next(); function rewind(); function valid(); }

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ITERATORS class EvacuationProcedures implements Iterator { /** * Returns the current value * where the array is at */ function current(); function key(); function next(); function rewind(); function valid(); }

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ITERATORS class EvacuationProcedures implements Iterator { function current(); /** * Returns the pointer to * the current position */ function key(); function next(); function rewind(); function valid(); }

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ITERATORS class EvacuationProcedures implements Iterator { function current(); function key(); /** * Advances the pointer to * the next position */ function next(); function rewind(); function valid(); }

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ITERATORS class EvacuationProcedures implements Iterator { function current(); function key(); function next(); /** * Moves the pointer back * to the beginning */ function rewind(); function valid(); }

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ITERATORS class EvacuationProcedures implements Iterator { function current(); function key(); function next(); function rewind(); /** * Indicates whether there * are more values to go */ function valid(); }

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ABSTRACTION

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ABSTRACTION function numberForPatient($patient) { return Registry::getNewNumber($patient); } function admitPatients(array $patients) { $numbers = array_map( "numberForPatient", $patients ); for ($i = 0; $i < count($patients); $i++) { Station::assignPatientToRoom( $numbers[$i], $patients[$i] ); } }

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ABSTRACTION class Patients implements Iterator { // ... function key() { return $this->patients[ $this->pointer ]; } function current() { return numberForPatient( $this->key() ); } }

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ABSTRACTION $intake = [ "Cathy", "Cal", "Joe", ]; $patients = new Patients($intake); foreach ($patients as $patient => $number) { Station::assignPatientToRoom( $number, $patient ); }

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ABSTRACTION class ClassifiedPatients implements Iterator { // ...construct($patients) function key() { return md5( $this->patients->key() ); } }

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ABSTRACTION $intake = [ "Cathy", "Cal", "Joe", ]; $patients = new ClassifiedPatients( new Patients($intake) ); foreach ($patients as $patient => $number) { Station::assignPatientToRoom( $number, $patient ); }

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ABSTRACTION class SearchablePatients implements IteratorAggregate { // ...construct($patients) function getIterator() { return $this->patients; } function searchFor($patient) { $i = 0; for ($this->patients as $next => $number) { if ($patient == $next) { return $i; } $i++; } } }

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ABSTRACTION class CountablePatients implements IteratorAggregate, Countable { // ...construct($patients) function count() { return iterator_count($this->patients); } } $countable = new CountablePatients( new Patients($intake) ); count($countable); // 㱺 3

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ABSTRACTION class SeekablePatients implements IteratorAggregate, SeekableIterator { // ...construct($patients) function seek($position) { $i = 0; foreach ($this->patients as $patient) { if ($i++ == $position) { return; } } } } $seekable = new SeekablePatients( new Patients($intake) ); $seekable ->seek(1) ->current(); // 㱺 "Cal"

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ABSTRACTION class ArrayablePatients implements IteratorAggregate, ArrayAccess { // ...construct($patients) function offsetExists($offset); function offsetGet($offset); function offsetSet($offset, $value); function offsetUnset($offset); } $array = new ArrayablePatients( new Patients($intake) ); $array[1]; // 㱺 "Cal"

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ABSTRACTION • AppendIterator • ArrayIterator • CachingIterator • CallbackFilterIterator • DirectoryIterator • EmptyIterator • FilesystemIterator • FilterIterator • GlobIterator

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ABSTRACTION • InfiniteIterator • IteratorIterator • LimitIterator • Mul0pleIterator • NoRewindIterator • ParentIterator • RecursiveArrayIterator • RecursiveCachingIterator • RecursiveCallbackFilterIterator

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ABSTRACTION • RecursiveDirectoryIterator • RecursiveFilterIterator • RecursiveIteratorIterator • RecursiveRegexIterator • RecursiveTreeIterator • RegexIterator

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PROBLEMS $patients = new Patients($intake); array_filter($patients, function($number) { // 㱺 error });

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PROBLEMS // github.com/nikic/iter $patients = new Patients($intake); iter\filter(function($number) { // 㱺 ok }, $patients);

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PROBLEMS // github.com/nikic/iter $patients = new Patients($intake); iter\filter(function($number) { // 㱺 ok }, $patients);

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ABSTRACTION

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ABSTRACTION $instructions = ""; $chapters = file_get_contents( "delta/operating-manual.txt" ); foreach ($chapters as $chapter) { $instructions .= file_get_contents( "delta/operating-manual/" . $chapter ); } print "instructions: \n\n" . $instructions; print "you've escaped!";

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ABSTRACTION class OperatingManual implements Iterator { private $chapters; function __construct($file) { $this->chapters = file_get_contents( $file ); } }

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ABSTRACTION class OperatingManual implements Iterator { // ... private $chapter = 0; function rewind() { $this->chapter = 0; } function next() { $this->chapter++; } }

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ABSTRACTION class OperatingManual implements Iterator { // ... function key() { return $this->chapter[ $this->chapter ]; } function current() { return file_get_contents( $this->key() ); } function valid() { isset( $this->chapters[ $this->chapter ] ); } }

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ABSTRACTION $manual = new OperatingManual( "delta/operating-manual.txt" ); foreach ($manual as $chapter) { print "next chapter: \n\n" . $chapter; } print "you've escaped!";

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ABSTRACTION $manual = new OperatingManual( "delta/operating-manual.txt" ); foreach ($manual as $chapter) { print "next chapter: \n\n" . $chapter; } print "you've escaped!";

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ITERATOR LIKE THINGS function OperatingManual($file) { $handle = fopen($file, "r"); while (!feof($handle)) { yield file_get_contents( trim(fgets($handle)) ); } fclose($handle); } $manual = OperatingManual( "delta/operating-manual.txt" );

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ITERATOR LIKE THINGS print_r(get_class_methods($manual)); // 㱺 Array // ( // [0] => rewind // [1] => valid // [2] => current // [3] => key // [4] => next // [5] => send // [6] => throw // [7] => getReturn // [8] => __wakeup // )

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ARRAYS ARE LIKE ROLODEXES

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ASK FOR ITEM #3, AND YOU'LL GET ITEM #3

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IT'S PREDICTABLE

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FUNCTIONS ACT LIKE DATA TABLES

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PUT THE SAME THING IN...

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...YOU GET THE SAME THING OUT

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IT'S PREDICTABLE

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NULL OBJECT PATTERN

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NULL OBJECT PATTERN function arrayToObject(array $data) { $encoded = json_encode($data); return json_decode($encoded); } $report = arrayToObject([ "station" => [ "armory" => [ "safe" => [ "weapons" => "one rifle", ], ], ], ]);

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NULL OBJECT PATTERN function searchForWeapons($report) { return $report ->station ->armory ->safe ->weapons; } print searchForWeapons( arrayToObject(["station" => null]) ); // 㱺 error: accessing $armory on null

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NULL OBJECT PATTERN function searchForWeapons($report) { if ($station = $report->station) { if ($armory = $station->armory) { // ... } } }

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NULL OBJECT PATTERN class Maybe { private $value; function __construct($value) { $this->value = $value; } function __get($property) { if (is_object($this->value)) { return new static( $this->value->$property ); } } function value() { return $this->value; } }

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NULL OBJECT PATTERN function searchForWeapons($report) { return $report ->station ->armory ->safe ->weapons ->value(); } print searchForWeapons( arrayToObject(["station" => null]); ); // 㱺 null

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NULL OBJECT PATTERN static function from($value) { if ($value instanceof static) { return $value; } return new static($value); } static function generator($starting, $generator) { $monad = static::from($starting); $generator = $generator($monad); $next = $generator->current(); while ($generator->valid()) { $monad = static::from($next); $next = $generator->send($monad); } return $generator->getReturn(); }

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NULL OBJECT PATTERN $weapons = Maybe::generator( $report, function($report) { $station = yield $report->station; $armory = yield $station->armory; $safe = yield $armory->safe; return $safe->weapons; } ); print $weapons;

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COROUTINES

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COROUTINES $people = [ "Lorna", "Rob", "Chris", "Aaron", "Sara", ]; $fences = [ "next to the old car", "behind the kennel", "out back", ];

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COROUTINES function checkRations(array $people) { foreach ($people as $person) { print "checking rations for " . $person; yield showRationsFor($person); } } function watchFences(array $people, array $fences) { foreach ($fences as $fence) { $next = next($people); if ($next) { $next = reset($people); } print $next . " is watching " . $fence; yield watchFence($next, $fence); } }

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COROUTINES class Task { private $generator; function __construct($generator) { $this->generator = $generator; } function run() { $this->generator->next(); } function valid() { return $this->generator->valid(); } }

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COROUTINES class Manager { private $tasks = []; function addTask(Task $task) { array_unshift($this->tasks, $task); } function run() { while (count($this->tasks)) { $next = array_pop($this->tasks); $next->run(); if ($next->valid()) { $this->addTask($next); } } } }

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COROUTINES $manager = new Manager(); $manager->addTask( new Task(checkRations($people) ); $manager->addTask( new Task(watchFences($people, $fences) ); $manager->run(); // 㱺 checking rations for Lorna // 㱺 Lorna is watching next to the old car // 㱺 checking rations for Rob // 㱺 Rob is watching behind the kennel // 㱺 checking rations for Chris // 㱺 Chris is watching out back // 㱺 checking rations for Aaron // 㱺 checking rations for Sara

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COROUTINES $manager = new Manager(); $manager->addTask( new Task(checkRations($people) ); $manager->addTask( new Task(watchFences($people, $fences) ); $manager->run(); // 㱺 checking rations for Lorna // 㱺 Lorna is watching next to the old car // 㱺 checking rations for Rob // 㱺 Rob is watching behind the kennel // 㱺 checking rations for Chris // 㱺 Chris is watching out back // 㱺 checking rations for Aaron // 㱺 checking rations for Sara

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