Rethinking Loops

John Kary • @johnkary

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

APL (1960s)

J (1990)

What if we used arrays for (almost) everything?

Functional Programming

Clojure (2007)


(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

Map

1,                  2,
2,                  4,
3,  -->  f(x)  -->  6,
4,                  8,
5,                  10,


// 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]

Filter

1,
2,                  2,
3,  -->  f(x)  -->
4,                  4,
5,
6,                  6,


// 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]

Reduce

1,
2,
3,  -->  f(x)  -->  15
4,
5,


// 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

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);

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

Local Variables


$method = "GET";

sayHello('John');

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

Global Variables


$method = "GET";

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

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

Closure Variables


$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;
    }
}

array_* accepts all 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?


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'];

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') {
    // ...
}

If/Else vs Switch/Case


if ($number === 1) {
    // Do something
} else if ($number === 2) {
    // Do something else
} else {
    // Last case
}


switch ($number) {
    case 1:
        // Do something
        break;
    case 2:
        // Do something else
        break;
    default:
        // Last case
        break;

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

The Future in PHP?

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

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]);
}


$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

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
Wolves painting
s278.photobucket.com/user/trueSoulWolfDemon/media/Wolves/Wolvesb.jpg.html
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

Questions?

John Kary • @johnkary

Slides: johnkary.net/talks
Feedback: joind.in/talk/f9bb3

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

Handling Errors?

Railway Oriented Programming:
A functional approach to error handling
fsharpforfunandprofit.com/rop/

:)

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

FizzBuzz

Functional Programming

Functional Programming Concepts

Map

Filter

Reduce

Expressive Language

Expressive Language

Expressive Language

Expressive Code

array_map

array_filter

array_reduce

Callables

Global functions

Static functions

Object methods

Anonymous functions

Scope

Local Variables

Global Variables

Closure Variables

array_* accepts many callables

array_* accepts all 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

If/Else vs Switch/Case

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!

The Future in PHP?

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

Homework

Bugs cannot existin code that doesn't exist

Be Expressive

Thanks.

Sources

Questions?

Performance?

Benchmark!

Handling Errors?

:)

Why Arrays?

Why Arrays?

Why Arrays?

Why Arrays?

Why Arrays?

:)

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