Rethinking Loops

John Kary • @johnkary

Kansas City to New Orleans

~700 mi or ~1100 km

FizzBuzz

Print numbers from 1 to 100, but...
For multiples of 3 print "Fizz"
For multiples of 5 print "Buzz"
For multiples of both 3 and 5 print "FizzBuzz"


$ php fizzbuzz.php
1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz
16
...
Buzz


foreach (range(1,100) as $num) {
    $output = '';

    if (0 === $num % 3) {
        $output .= 'Fizz';
    }

    if (0 === $num % 5) {
        $output .= 'Buzz';
    }

    if (!$output) {
        $output = $num;
    }

    echo $output . "\n";
}


$max = 100;
$all = range(1, $max);
$threes = array_fill_keys(range(3, $max, 3), 'Fizz'); // [3 => 'Fizz', 6 => 'Fizz']
$fives = array_fill_keys(range(5, $max, 5), 'Buzz');  // [5 => 'Buzz', 10 => 'Buzz']
$fifteens = array_fill_keys(range(15, $max, 15), 'FizzBuzz'); // [15 => 'FizzBuzz']

echo join("\n", array_replace($all, $threes, $fives, $fifteens));

By Jeff Madsen @codebyjeff

What if we used arrays for (almost) everything?

Collection Oriented Programming

Functional Programming


(defn encode
  [#^InputStream input #^Writer output #^String alphabet line-length]
  (let [buffer (make-array Byte/TYPE 3)]
    (loop [line 0]
      (let [len (.read input buffer)]
        (when (pos? len)
          (let [b0 (Integer/valueOf (int (aget buffer 0)))
                b1 (Integer/valueOf (int (aget buffer 1)))
                b2 (Integer/valueOf (int (aget buffer 2)))]
            (cond (= len 3)
                  (let [s0 (bit-and 0x3F (bit-shift-right b0 2))
                        s1 (bit-and 0x3F
                                    (bit-or (bit-shift-left b0 4)
                                            (bit-shift-right b1 4)))
                        s2 (bit-and 0x3F
                                    (bit-or (bit-shift-left b1 2)
                                            (bit-shift-right b2 6)))
                        s3 (bit-and 0x3F b2)]
                    (.append output (.charAt alphabet s0))
                    (.append output (.charAt alphabet s1))
                    (.append output (.charAt alphabet s2))
                    (.append output (.charAt alphabet s3))))))))))

Functional Programming Concepts

Functional Concepts

Map -- 1:1 transform
- Onions ==> Chopped Onions
Filter -- Only keep items where a condition returns true
- Keep only fresh Limes
Reduce -- Combine ingredients into something new!
- Wet ingredients + Dry ingredients

array_map


// array_map ( callable $callback , array $array1 [, array $... ] )

$start = [1, 2, 3, 4, 5];
$fn = function ($i) {
    return $i * 2;
};
$end = array_map($fn, $start);

// [2, 4, 6, 8, 10]

array_filter


// array_filter ( array $array [, callable $callback [, int $flag = 0 ]] )

$start = [1, 2, 3, 4, 5, 6];
$even = array_filter($start, function ($i) {
    return $i % 2 === 0;
});

// [2, 4, 6]

array_reduce


// array_reduce ( array $array , callable $callback [, mixed $initial = NULL ] )

$start = [1, 2, 3, 4, 5];
$end = array_reduce($start, function ($total, $i) {
    return $total + $i;
}, 0);

// 15

Voltron: teaching kids distributed computing since 1984
Chris Paul @idiosynchris

Expressive Language

Cool

Expressive Language

Chess is cool
Roller coasters are cool
Playing chess on a roller coaster is cool

Expressive Language

Chess is contemplative
Roller coasters are thrilling
Playing chess on a roller coaster is connivingly rebellious

Expressive Code

array_map


$start = [1, 2, 3, 4, 5];
$end = [];

for ($i=0; $i < count($start); $i++) {
    $current = $start[$i];
    $end[] = $current * 2;
}

// $end [2, 4, 6, 8, 10]


$start = [1, 2, 3, 4, 5];
$end = array_map(function ($i) {
    return $i * 2;
}, $start);

// $end [2, 4, 6, 8, 10]

array_filter


$start = [1, 2, 3, 4, 5, 6];
$even = [];

foreach ($start as $i) {
    if ($i % 2 === 0) {
        $even[] = $i;
    }
}

// $even [2, 4, 6]


$start = [1, 2, 3, 4, 5, 6];
$even = array_filter($start, function ($i) {
    return $i %2 === 0;
});

// $even [2, 4, 6]

array_reduce


$scores = [1, 2, 3, 4, 5];
$sum = 0;

foreach ($scores as $s) {
    $sum = $sum + $s;
}

// $sum === 15


$scores = [1, 2, 3, 4, 5];
$sum = array_reduce($scores, function ($end, $i) {
    return $end + $i;
}, 0);

// $sum === 15
// $sum = array_sum($start);

Users who are minors


$data = [
    ['age' => 31, 'name' => 'John'],
    ['age' => 12, 'name' => 'Jamie'],
    ['age' => 8, 'name' => 'Megan'],
];
$users = array_map(function($u) { return (object) $u; }, $data);

// array(3) {
//   [0] => class stdClass#2 (2) {
//     public $age => int(31)
//     public $name => string(4) "John"
//   }
//   [1] => class stdClass#3 (2) {
//      public $age => int(12)
//      public $name => string(5) "Jamie"
//   }
//   [2] => class stdClass#4 (2) {
//     public $age => int(8)
//     public $name => string(5) "Megan"
//   }
// }

Users who are minors


$minors = array_filter($users, function($user) {
    return $user->age < 18;
});

// [Jamie, Megan]


count($minors); // int(2)

Users who are minors


$minors = array_reduce($users, function($count, $user) {
    return $count + (int) ($user->age < 18);
});

// int(2)

Callables

Global functions


function sayHello($name) {
    return 'Hello ' . $name;
}

echo sayHello('John'); // "Hello John"

Static functions


class User {
    public static function sayHello($name) {
        return 'Hello ' . $name;
    }
}

echo User::sayHello("John"); // "Hello John"

Object methods


class User {
    private $name;

    public function __construct($name) {
        $this->name = $name;
    }

    public function getGreeting() {
        return 'Hello ' . $this->name;
    }
}

$user = new User("John");
echo $user->getGreeting(); // "Hello John"

Anonymous functions


$greeting = function ($name) {
    return 'Hello ' . $name;
};

echo $greeting('John'); // "Hello John"

Scope


$method = "GET";

sayHello('John');

function sayHello($name) {
    return 'Hello ' . $name . ' via ' . $method;
    // PHP Notice:  Undefined variable: method
}

Scope


$method = "GET";

sayHello('John');
// "Hello John via GET"

function sayHello($name) {
    global $method;
    return 'Hello ' . $name . ' via ' . $method;
}

Scope


$method = "GET";

function sayHello($name, $verb) {
    return sprintf('Hello %s via %s', $name, $verb);
}

echo sayHello('John', $method); // "Hello John via GET"

Scope


function sayHello($name) {
    return 'Hello ' . $name;
}

sayHello('John'); // "Hello John"
echo $name;
// `PHP Notice: Undefined variable: name ...`
// because $name is not accessible in enclosing scope

Scope


$method = "GET";

$greeting = function($name) use ($method) {
    return sprintf('Hello %s via %s', $name, $method);
};

echo $greeting('John'); // "Hello John via GET"

array_* accepts many callables


class User {
    private $name, $age;

    public static function fromArray(array $data)
    {
        $u = new User;
        $u->name = $data['name'];
        $u->age = $data['age'];
        return $u;
    }
}

$rows = [
    ['name' => 'Sarah', 'age' => 58],
    ['name' => 'Matt', 'age' => 52],
    ['name' => 'Mickey', 'age' => 42],
];

array_* accepts many callables


$rows = [
    ['name' => 'Sarah', 'age' => 58],
    ['name' => 'Matt', 'age' => 52],
    ['name' => 'Mickey', 'age' => 42],
];

// Anonymous
$build = function(array $row) {
    return User::fromArray($row);
};
$users = array_map($build, $rows);


// Below are all equivalent
$users = array_map('User::fromArray', $rows);
$users = array_map(['User', 'fromArray'], $rows);

$u = new User();
$users = array_map([$u, 'fromArray'], $rows);

Be nice to your brain!


for ($i = 0, $for_max = count($cached_inserts); $i < $for_max; $i++) {
    if ($smarty->debugging) {
        $_params = array();
        require_once(SMARTY_CORE_DIR . 'core.get_microtime.php');
    }
    $args = unserialize($insert_args[$i]); $name = $args['name'];

    if (isset($args['script'])) {
        if(!smarty_core_get_php_resource($_params, $smarty)) {
            return false;
        }
        $php_resource = $_params['php_resource'];

        if ($resource_type == 'file') {
            $smarty->_include($php_resource, true);
        } else {
            $smarty->_eval($php_resource);
        }
    }

    $params['results'] = substr_replace($params['results'], $replace, strpos($params['results'], $cached_inserts[$i]), strlen($cached_inserts[$i]));
    if ($smarty->debugging) {
        $_params = array();
        require_once(SMARTY_CORE_DIR . 'core.get_microtime.php');
        $smarty->_smarty_debug_info[] = array('type'      => 'insert',
                                              'exec_time' => smarty_core_get_microtime($_params, $smarty) - $debug_start_time);
    }
}

return $params['results'];

for ($i = 0, $for_max = count($cached_inserts); $i < $for_max; $i++) {
function doComplicatedThing() {
    for ($i = 0, $for_max = count($cached_inserts); $i < $for_max; $i++) {
        if ($smarty->debugging) {
            $_params = array();
            require_once(SMARTY_CORE_DIR . 'core.get_microtime.php');
        }
        $args = unserialize($insert_args[$i]); $name = $args['name'];

        if (isset($args['script'])) {
            if(!smarty_core_get_php_resource($_params, $smarty)) {
                return false;
            }
            $php_resource = $_params['php_resource'];

            if ($resource_type == 'file') {
                $smarty->_include($php_resource, true);
            } else {
                $smarty->_eval($php_resource);
            }
        }

        $params['results'] = substr_replace($params['results'], $replace, strpos($params['results'], $cached_inserts[$i]), strlen($cached_inserts[$i]));
        if ($smarty->debugging) {
            $_params = array();
            require_once(SMARTY_CORE_DIR . 'core.get_microtime.php');
            $smarty->_smarty_debug_info[] = array('type'      => 'insert',
                                                  'exec_time' => smarty_core_get_microtime($_params, $smarty) - $debug_start_time);
        }
    }

    return $params['results'];
}

Working Memory

Dogs, Strips of Bacon, Gina

3 dogs run into the your living room
Gina feeds each dog a strip of bacon
- except Spackle because he pooped on the floor earlier
Spot wags her tail looking at you then rolls over
You're hungry and eat 2 strips of bacon from the oven set at 400°F
Gina hands you fresh bacon and you drop it because it's too hot
- 5 pieces fall to the ground
- No more bacon
How many bacon strips were prepared today?
How many bacon strips were eaten today?

Dogs, Strips of Bacon, Gina

3 dogs run into the your living room
Gina feeds each dog 2 dogs a strip of bacon
- except Spackle because he pooped on the floor earlier
Spot wags her tail looking at you then rolls over
You're hungry and eat 2 strips of bacon from the oven set at 400°F
Gina hands you more bacon and you drop it because it's too hot
- 5 pieces fall to the ground
- No more bacon
How many bacon strips were prepared today?
How many bacon strips were eaten today?

A program cannot change
until it is alive in a programmer's head.

–Jessica Kerr on Ruby Rogues Podcast

Nested Control Structures :(


$users = User::all();

foreach ($users as $user) {
    if (is_admin($user)) {
        echo "ID: " . $user->id . " Name: " . $user->name . "
";
        
        foreach ($user->groups as $group) {
            if (!in_array($group->admin, $users)) {
                continue;
            }
            echo "Group Admin: " . $user->name . "
";
        }
    } else {
        foreach ($user->activities as $activity) {
            echo "Activities: ";
            if ($activity->isActive()) {
                echo $activity->name . "
";
            }
        }
    }
}

Control Structure Anxiety


foreach (...) {
    if (...) {
        foreach (...) {
            if (...) {
                // ...
            }
        }
    } else {
        foreach (...) {
            if (...) {
                // ...
            }
        }
    }
}

New rules?
New variables?
Minor details vs New contexts

Readability :(


$customFieldValues = $this->getRequestParam("customFieldValues");
if ($customFieldValues) {
    foreach ($customFieldValues as $custValueInfo) {
        $valueEntry = $reservation->getCustomFieldValueEntry($custValueInfo['id']);
        // Not found, this is the first time they're setting the value, so we need
        // to create a new entry
        if (!$valueEntry) {
            $customField = $resource->getCustomField($custValueInfo['id']);
            if (!$customField) {
                throw new \InvalidArgumentException("Attempted to set a custom field that does not belong to the specified Resource");
            }

            $valueEntry = new ReservationCustomFieldValueEntry();
            $valueEntry->setField($customField);
            $reservation->addCustomFieldValue($valueEntry);
        }

        $valueEntry->setValue($custValueInfo['value']);
    }
}

Local variables are noisy :(


public function getOldestStudentAction(Request $request) {
    $method = $request->getMethod();
    if ($method !== 'PUT') {
        throw new \BadRequestMethod('Endpoint only accepts PUT requests');
    }

    $db = $this->getDatabase()->getConnection();
    $roster = $db->query('Roster', $request->get('roster_id'));

    $oldest = null;
    foreach ($roster->getStudents() as $student) {
        if (!$oldest || $student->getAge() > $oldest->getAge()) {
            $oldest = $student;
        }
    }

    $oldestName = $oldest->getName();
    echo "The oldest student is " . $oldestName . "\n";
    $db->close();
    $roster->updateLastAccess();

    // $method, $db, $roster, $request, $oldest, $student, $oldestName
}

Ruthlessly Eliminate Local Variables


$method = $request->getMethod();
if ($method !== 'POST') {
    // ...
}


if ($request->getMethod() !== 'POST') {
    // ...
}

Chain Method Calls


$db = $this->getDatabase();
$conn = $db->getConnection();
$roster = $conn->query('Roster', $request->get('roster_id'));


$roster = $this
    ->getDatabase()
    ->getConnection()
    ->query('Roster', $request->get('roster_id'));

array ==> map ==> filter ==> reduce


// 1. Multiply by 2
// 2. Remove any results over 9
// 3. Add numbers together


$start = [1, 2, 3, 4, 5];

echo array_reduce(array_filter(array_map(function ($i) {
    return $i * 2;
}, $start), function ($i) {
    return $i < 9;
}), function ($sum, $i) {
    return $sum + $i;
}, 0);

// "20"


array_map($fn, $array, [$...])
array_filter($array, $fn)
array_reduce($array, $fn, $initial)


$friends = ['John', 'Chris', 'Penelope', 'Megan'];

echo join(", ", addGreeting(keepUnderLength(6, $friends)));

// "Hello John, Hello Chris, Hello Megan"


$friends = ['John', 'Chris', 'Penelope', 'Megan'];

$short = keepUnderLength(6, $friends);
$greeted = addGreeting($short);
$result = join(", ", $greeted);

echo $result; // "Hello John, Hello Chris, Hello Megan"

Doug McIlroy
Inventor of Unix pipes in 1972^[1]

Unix Pipes


$ cat friends.txt
John
Chris
Penelope
Megan


$ cat friends.txt | awk 'length($0) < 6'
John
Chris
Megan


$ cat friends.txt | awk 'length($0) < 6' | xargs -L1 echo "Hello"
Hello John
Hello Chris
Hello Megan

Microservices can be data pipelines

c/o Samantha Quiñones, "Building Real-Time Metric Pipelines"

Pipelines


$friends = new \Haystack\HArray(['John', 'Chris', 'Penelope', 'Megan']);
$greetings = $friends->filter(...)->map(...)->toArray();

// ["Hello John", "Hello Chris", "Hello Megan"]


class HArray extends \ArrayObject
{
    private $array = [];
    public function __construct(array $a = []) {
        $this->array = $a;
    }
    public function map(callable $func) {
        return new static(array_map($func, $this->array));
    }
    public function filter(callable $func = null) {
        return new static(array_filter($this->array, $func));
    }
    public function reduce(callable $func, $initial = null) {
        return array_reduce($this->array, $func, $initial);
    }
}

Pipelines


$friends = new \Haystack\HArray(['John', 'Chris', 'Penelope', 'Megan']);
$greetings = $friends
    ->filter(...)
    ->map(...)
    ->reduce(...)
    ->toArray();

return $greetings;

Pipelines


$friends = new \Haystack\HArray(['John', 'Chris', 'Penelope', 'Megan']);
$greetings = $friends
    ->filter(function ($name) {
        return ...
    })
    ->map(function ($name) {
        return ...
    })
    ->reduce(function ($name) {
        return ...
    })
    ->toArray();

return $greetings;

Path to Completion

Luke Wroblewski
Web Form Design: Filling in the Blanks
lukew.com/resources/web_form_design.asp

Pipelines


// 1. Multiply by 2
// 2. Remove any results over 9
// 3. Add numbers together

$start = [1, 2, 3, 4, 5];

echo (new \Haystack\HArray($start))
    ->map(function ($i) {
        return $i * 2;
    })
    ->filter(function ($i) {
        return $i < 9;
    })
    ->reduce(function ($sum, $i) {
        return $sum + $i;
    });

// 20

Refactor to Pipelines

Exercise: Find all classes to instantiate


$ tree /projects/loops/src
src
└── FizzBuzz
    ├── Canonical.php            class Canonical {}
    ├── Haystack.php             class Haystack {}
    └── SomeInterface.php        interface SomeInterface {}


kataProvider('FizzBuzz');
// [  "\\RethinkingLoops\\FizzBuzz\\Canonical",
//    "\\RethinkingLoops\\FizzBuzz\\Haystack" ]


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);
    $classes = [];
    foreach (scandir($src) as $filename) {
        // [  ".",
        //    "..",
        //    "Canonical.php",
        //    "Haystack.php",
        //    "SomeInterface.php" ]
    }

    return $classes;
}


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);

    $classes = [];
    foreach (scandir($src) as $filename) {
        $path = sprintf('%s/%s', $src, $filename);
        // [
        //     "/projects/loops/src/FizzBuzz/.",
        //     "/projects/loops/src/FizzBuzz/..",
        //     "/projects/loops/src/FizzBuzz/Canonical.php",
        //     "/projects/loops/src/FizzBuzz/Haystack.php",
        //     "/projects/loops/src/FizzBuzz/SomeInterface.php",
        // ]
    }

    return $classes;
}


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);

    $classes = [];
    foreach (scandir($src) as $filename) {
        $path = sprintf('%s/%s', $src, $filename);
        if (false === is_dir($path)) {
            // [
            //     "/projects/loops/src/FizzBuzz/Canonical.php",
            //     "/projects/loops/src/FizzBuzz/Haystack.php",
            //     "/projects/loops/src/FizzBuzz/SomeInterface.php",
            // ]
        }
    }

    return $classes;
}


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);

    $classes = [];
    foreach (scandir($src) as $filename) {
        $path = sprintf('%s/%s', $src, $filename);
        if (false === is_dir($path)) {
            $path = str_replace('.php', '', $path);
            // [
            //     "/projects/loops/src/FizzBuzz/Canonical",
            //     "/projects/loops/src/FizzBuzz/Haystack",
            //     "/projects/loops/src/FizzBuzz/SomeInterface",
            // ]
        }
    }

    return $classes;
}


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);

    $classes = [];
    foreach (scandir($src) as $filename) {
        $path = sprintf('%s/%s', $src, $filename);
        if (false === is_dir($path)) {
            $path = str_replace('.php', '', $path);
            $fqcn = str_replace($src . '/', '\\RethinkingLoops\\' . $dir . '\\', $path);
            // [
            //     "\\RethinkingLoops\\FizzBuzz\\Canonical",
            //     "\\RethinkingLoops\\FizzBuzz\\Haystack",
            //     "\\RethinkingLoops\\FizzBuzz\\SomeInterface",
            // ]
        }
    }

    return $classes;
}


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);

    $classes = [];
    foreach (scandir($src) as $filename) {
        $path = sprintf('%s/%s', $src, $filename);
        if (false === is_dir($path)) {
            $path = str_replace('.php', '', $path);
            $fqcn = str_replace($src . '/', '\\RethinkingLoops\\' . $dir . '\\', $path);

            $r = new \ReflectionClass($fqcn);
            if (false === $r->isAbstract()) {
                $classes[] = $fqcn;
            }
            // [ "\\RethinkingLoops\\FizzBuzz\\Canonical",
            //   "\\RethinkingLoops\\FizzBuzz\\Haystack" ]
        }
    }

    return $classes;
}


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);

    $classes = [];
    foreach (scandir($src) as $filename) {
        $path = sprintf('%s/%s', $src, $filename);
        if (false === is_dir($path)) {
            $path = str_replace('.php', '', $path);
            $fqcn = str_replace($src . '/', '\\RethinkingLoops\\' . $dir . '\\', $path);

            $r = new \ReflectionClass($fqcn);
            if (false === $r->isAbstract()) {
                $classes[] = $fqcn;
                // $dir, $src, $classes, $filename, $path, $fqcn, $r
            }
        }
    }

    return $classes;
}

Refactor to array_*


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);

    $paths = array_map(function ($filename) use ($src) {
        return sprintf('%s/%s', $src, $filename);
    }, scandir($src));

    $files = array_filter($paths, function ($path) {
        return false === is_dir($path);
    });

    $allClasses = array_map(function ($path) use ($src, $dir) {
        $path = str_replace('.php', '', $path);
        return str_replace($src . '/', '\\RethinkingLoops\\' . $dir . '\\', $path);
    }, $files);

    return array_filter($allClasses, function ($class) {
        return false === (new \ReflectionClass($fqcn))->isAbstract();
    });
}

Refactor to Pipeline


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);
    // "/projects/loops/src/FizzBuzz/"

    return (new \Haystack\HArray(scandir($src)))
        // [
        //    ".",
        //    "..",
        //    "Canonical.php",
        //    "Haystack.php",
        //    "SomeInterface.php",
        // ]
}


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);

    return (new \Haystack\HArray(scandir($src)))
        ->map(function ($filename) use ($src) {
            return sprintf('%s/%s', $src, $filename);
        })
        // [
        //     "/projects/loops/src/FizzBuzz/.",
        //     "/projects/loops/src/FizzBuzz/..",
        //     "/projects/loops/src/FizzBuzz/Canonical.php",
        //     "/projects/loops/src/FizzBuzz/Haystack.php",
        //     "/projects/loops/src/FizzBuzz/SomeInterface.php",
        // ]
}


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);

    return (new \Haystack\HArray(scandir($src)))
        ->map(function ($filename) use ($src) {
            return sprintf('%s/%s', $src, $filename);
        })
        ->filter(function ($path) {
            return false === is_dir($path);
        })
        // [
        //     "/projects/loops/src/FizzBuzz/Canonical.php",
        //     "/projects/loops/src/FizzBuzz/Haystack.php",
        //     "/projects/loops/src/FizzBuzz/SomeInterface.php",
        // ]
}


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);

    return (new \Haystack\HArray(scandir($src)))
        ->map(function ($filename) use ($src) {
            return sprintf('%s/%s', $src, $filename);
        })
        ->filter(function ($path) {
            return false === is_dir($path);
        })
        ->map(function ($filepath) use ($src, $dir) {
            $filepath = str_replace('.php', '', $filepath);
            return str_replace($src . '/', '\\RethinkingLoops\\' . $dir . '\\', $filepath);
        })
        // [ "\\RethinkingLoops\\FizzBuzz\\Canonical",
        //   "\\RethinkingLoops\\FizzBuzz\\Haystack",
        //   "\\RethinkingLoops\\FizzBuzz\\SomeInterface" ]
}


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);

    return (new \Haystack\HArray(scandir($src)))
        ->map(function ($filename) use ($src) {
            return sprintf('%s/%s', $src, $filename);
        })
        ->filter(function ($path) {
            return false === is_dir($path);
        })
        ->map(function ($filepath) use ($src, $dir) {
            $filepath = str_replace('.php', '', $filepath);
            return str_replace($src . '/', '\\RethinkingLoops\\' . $dir . '\\', $filepath);
        })
        ->filter(function ($fqcn) {
            return false === (new \ReflectionClass($fqcn))->isAbstract();
        })
        ->toArray();
        // [ "\\RethinkingLoops\\FizzBuzz\\Canonical",
        //   "\\RethinkingLoops\\FizzBuzz\\Haystack" ]
}


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);

    return (new \Haystack\HArray(scandir($src)))
        ->map(function ($filename) use ($src) {
            return sprintf('%s/%s', $src, $filename);
        })
        ->filter(function ($path) {
            return false === is_dir($path);
        })
        ->map(function ($filepath) use ($src, $dir) {
            $filepath = str_replace('.php', '', $filepath);
            return str_replace($src . '/', '\\RethinkingLoops\\' . $dir . '\\', $filepath);
        })
        ->filter(function ($fqcn) {
            return false === (new \ReflectionClass($fqcn))->isAbstract();
        })
        ->toArray();
}

Available Today!

Haystack - github.com/ericpoe/haystack
Laravel Collections - laravel.com/docs/5.2/collections
Doctrine Collections - github.com/doctrine/collections

Compatible with Drupal 8!


$ composer require ericpoe/haystack 2.0.x-dev

Collection, Iteration, Pipeline libraries (in no order)

transducers-php - github.com/mtdowling/transducers.php
Knapsack - github.com/DusanKasan/Knapsack
Non-standard PHP library (NSPL) - github.com/ihor/Nspl
League\Pipeline - pipeline.thephpleague.com
nikic/iter - github.com/nikic/iter
PHP-DS Extension - http://tiny.cc/phpds

The Future?

PHP RFC: Pipe Operator |>


$response = loadConfig()
    |> buildDic($$)
    |> getApp($$)
    |> getRouter($$)
    |> getDispatcher($$, $request)
    |> dispatchBusinessLogic($$, $request, new Response())
    |> renderResponse($$)
    |> buildPsr7Response($$)
    |> emit($$);

wiki.php.net/rfc/pipe-operator

In discussion, targeting PHP 7.2

PHP RFC: Pipe Operator |>


function kataProvider($dir) {
    $src = realpath(__DIR__ . '/../src/' . $dir);

    return scandir($src)
        |> array_map(function ($filename) use ($src) {
            return sprintf('%s/%s', $src, $filename);
        }, $$)
        |> array_filter($$, function ($path) {
            return false === is_dir($path);
        })
        |> array_map(function ($filepath) use ($src, $dir) {
            $filepath = str_replace('.php', '', $filepath);
            return str_replace($src . '/', '\\RethinkingLoops\\' . $dir . '\\', $filepath);
        }, $$)
        |> array_filter($$, function ($fqcn) {
            return false === (new \ReflectionClass($fqcn))->isAbstract();
        });
}

wiki.php.net/rfc/pipe-operator

In discussion, targeting PHP 7.2

PHP RFC: Arrow Functions


$elements = [1, 3, 5];

// live
$result = array_map(function($x) { return $x * 2; }, $elements);
 
// proposed
$result = array_map(function($x) => $x * 2, $elements);

wiki.php.net/rfc/arrow_functions

In discussion, targeting PHP 7.2

PHP RFC: Arrow Functions


$friends = new \Haystack\HArray(['John', 'Chris', 'Penelope', 'Megan']);

$greetings = $friends
    ->filter(function ($name) => strlen($name) < 6)
    ->map(function ($name) => 'Hello ' . $name);

echo join(", ", $greetings->toArray());
// "Hello John, Hello Chris, Hello Megan"

wiki.php.net/rfc/arrow_functions

In discussion, targeting PHP 7.2

Rethinking Loops Playground


$ composer create-project johnkary/rethinking-loops

Your Homework

Collection Pipeline Design Techniques
infoq.com/presentations/collection-pipelines
Martin Fowler on Pipelines
martinfowler.com/articles/collection-pipeline/
Refactoring To Collections
adamwathan.me/refactoring-to-collections/
The Art of Unix Programming
catb.org/esr/writings/taoup/html/
Functional JavaScript
shop.oreilly.com/product/0636920028857.do
Seven Languages in Seven Weeks
pragprog.com/book/btlang/seven-languages-in-seven-weeks
Structure and Interpretation of Computer Programs (SICP) - mitpress.mit.edu/sicp/full-text/book/book.html


(defn encode
  [#^InputStream input #^Writer output #^String alphabet line-length]
  (let [buffer (make-array Byte/TYPE 3)]
    (loop [line 0]
      (let [len (.read input buffer)]
        (when (pos? len)
          (let [b0 (Integer/valueOf (int (aget buffer 0)))
                b1 (Integer/valueOf (int (aget buffer 1)))
                b2 (Integer/valueOf (int (aget buffer 2)))]
            (cond (= len 3)
                  (let [s0 (bit-and 0x3F (bit-shift-right b0 2))
                        s1 (bit-and 0x3F
                                    (bit-or (bit-shift-left b0 4)
                                            (bit-shift-right b1 4)))
                        s2 (bit-and 0x3F
                                    (bit-or (bit-shift-left b1 2)
                                            (bit-shift-right b2 6)))
                        s3 (bit-and 0x3F b2)]
                    (.append output (.charAt alphabet s0))
                    (.append output (.charAt alphabet s1))
                    (.append output (.charAt alphabet s2))
                    (.append output (.charAt alphabet s3))))))))))


$list = [2, 4, 6, 8, 10];

for ($i=0; $i < count($list); $i++) {
    $current = $start[$i];
    $end[] = $current = *;
}

foreach ($list as $idx => $value) {
    echo $value;
    unset($list[$idx]);
}

Bugs cannot exist
in code that doesn't exist

Be Expressive

Thanks.

Sources

Title slide background
https://www.flickr.com/photos/tbrianjones/22135624309/
FizzBuzz without control structures tweet by John Kary
twitter.com/johnkary/status/596163674743644160
Voltron tweet by Chris Paul @idiosynchris
twitter.com/idiosynchris/status/719565179801853954
Playing chess on roller coasters (xkcd)
xkcd.com/chesscoaster/
This is why you shouldn't interrupt a programmer
twitter.com/detly/status/394755439314755584
Building Real-Time Data Pipelines by Samantha Quiñones
joind.in/event/sunshinephp-2016/building-real-time-data-pipelines
Best Practices For Form Design by Luke Wroblewski
static.lukew.com/webforms_lukew.pdf
Picture of Douglas McIlroy
en.wikipedia.org/wiki/Douglas_McIlroy
Adam Wathan pipeline code tweet
twitter.com/adamwathan/status/666819102581788672
This Is Not A Pipe
www.wikiart.org/en/rene-magritte/the-treachery-of-images-this-is-not-a-pipe-1948

Join us for Sprints!

Friday, May 13
Convention Center

	Time	Room
First-Time Sprinter Workshop	9am-12pm	271-273
Mentored Core Sprint	9am-6pm	275-277
General Sprints	9am-6pm	278-282

Questions?

John Kary • @johnkary

Slides: johnkary.net/talks
Feedback: http://bit.ly/rethinking-loops-feedback1

Rethinking Loops by John Kary is licensed under a
Creative Commons Attribution-ShareAlike 4.0 International License.

Performance?

Arrays vs Objects Benchmarks (5.6, 7.0)
http://bit.ly/rethinking-loops-perf-1
Why objects (usually) use less memory than arrays in PHP
http://bit.ly/rethinking-loops-perf-2

Benchmark!

https://blackfire.io

:)

Why Arrays?

Quantity	One	Arrays
NULL	null	[]
0	null	[]
1	new User()	[new User()]
3	:(	[ new User(), new User(), new User(), ]
a lot	:(	[...]

Why Arrays?


/** @param User[]|User|null $users */
function findUserGroups($users) {
    if ($users === null) return null;

    if ($users instanceof User) {
        $groups = Group::findByUser($users->id);
        return $groups;
    }

    if (count($users) === 0) {
        return [];
    } else {
        $groups = [];
        foreach ($users as $user) {
            $userGroups = Group::findByUser($user->id);
            if (!$groups) continue;
            $groups = array_merge($groups, $userGroups);
        }
    }

    return $groups;
}

Why Arrays?


/** @param User[]|User|null $users */
function findUserGroups($users) {
    $groups = [];

    foreach ((array) $users as $user) {
        $userGroups = Group::findByUser($user->id);
        if (!$groups) continue;
        $groups = array_merge($groups, $userGroups);
    }

    return $groups;
}

Why Arrays?


/** @param User[]|User|null $users */
function findUserGroups($users) {
    $groups = [];

    foreach ((array) $users as $user) {
        $groups = array_merge($groups, (array) Group::findByUser($user->id));
    }

    return $groups;
}

Why Arrays?


function findUserGroups($users) {
    return array_reduce((array) $users, function ($groups, $user) {
        return array_merge($groups, (array) Group::findByUser($user->id));
    }, []);
}

Rethinking Loops

Kansas City to New Orleans

~700 mi or ~1100 km

FizzBuzz

Functional Programming Concepts

Functional Concepts

array_map

array_filter

array_reduce

Expressive Language

Cool

Expressive Language

Expressive Language

Expressive Code

array_map

array_filter

array_reduce

Users who are minors

Users who are minors

Users who are minors

Callables

Global functions

Static functions

Object methods

Anonymous functions

Scope

Scope

Scope

Scope

Scope

Scope

array_* accepts many callables

array_* accepts many callables

Be nice to your brain!

Working Memory

Dogs, Strips of Bacon, Gina

Dogs, Strips of Bacon, Gina

A program cannot changeuntil it is alive in a programmer's head.

–Jessica Kerr on Ruby Rogues Podcast

Nested Control Structures :(

Control Structure Anxiety

Readability :(

Local variables are noisy :(

Ruthlessly Eliminate Local Variables

Chain Method Calls

array ==> map ==> filter ==> reduce

Doug McIlroyInventor of Unix pipes in 1972[1]

Unix Pipes

Microservices can be data pipelines

Pipelines

Pipelines

Pipelines

Path to Completion

Luke Wroblewski Web Form Design: Filling in the Blanks lukew.com/resources/web_form_design.asp

Pipelines

Refactor to Pipelines

Exercise: Find all classes to instantiate

Refactor to array_*

Refactor to Pipeline

Available Today!

Compatible with Drupal 8!

Collection, Iteration, Pipeline libraries (in no order)

The Future?

PHP RFC: Pipe Operator |>

In discussion, targeting PHP 7.2

PHP RFC: Pipe Operator |>

In discussion, targeting PHP 7.2

PHP RFC: Arrow Functions

In discussion, targeting PHP 7.2

PHP RFC: Arrow Functions

In discussion, targeting PHP 7.2

Rethinking Loops Playground

Your Homework

Bugs cannot existin code that doesn't exist

Be Expressive

Thanks.

Sources

Join us for Sprints!

Friday, May 13Convention Center

Questions?

A program cannot change
until it is alive in a programmer's head.

Doug McIlroy
Inventor of Unix pipes in 1972^[1]

Luke Wroblewski
Web Form Design: Filling in the Blanks
lukew.com/resources/web_form_design.asp

Bugs cannot exist
in code that doesn't exist

Friday, May 13
Convention Center