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Witek Adamus
PHPCon 2016, Rawa Mazowiecka
Why async and functional programming in PHP7 suck and how to get over it?
Who am I?
5 years of
imperative
programming
2 years of
functional
programming
Back to
PHP7
❏ What can functional programming bring to the table?
❏ When language can be described as functional?
Table of content
❏ DIY: cleaning ❏ Transparent parallelism❏ Parallelism vs Concurrency
❏ Parallel collections
Table of content
Pros and cons of functional programming
Pros Cons
Efficiency Efficiency
Entry threshold Entry threshold
Mathematical description of
reality
Mathematical description of
reality
Pros and cons of functional programming
Pros Cons In result
Efficiency Efficiency Scalability
Entry threshold Entry threshold Let’s get the party started
Mathematical description of
reality
Mathematical description of
reality
Shorter and more descriptive code
public function someMethodWithMisleadingName( array $mysteriousInput){ $arr = []; foreach ($mysteriousInput as $inp) { if ($inp > 10) { $arr[] = $inp; } } $arrLeft = $arrRight = $arrCenter = []; foreach ($arr as $elem) { $bucket = $elem <=> 20; if ($bucket < 0) { $arrLeft[] = $elem; } if ($bucket == 0) { $arrCenter[] = $elem; } if ($bucket > 0) { $arrRight[] = $elem;} } $countLeft = count($arrLeft); $countCenter = count($arrCenter); $countRight = count($arrRight); return array_sum([$countLeft, $countCenter, $countRight]) / 3;}
public function someMethodWithMisleadingName( array $mysteriousInput) { $arr = []; foreach ($mysteriousInput as $inp) { if ($inp > 10) { $arr[] = $inp; } }
$arrLeft = $arrRight = $arrCenter = []; foreach ($arr as $elem) { $bucket = $elem <=> 20; if ($bucket < 0) { $arrLeft[] = $elem; } if ($bucket == 0) { $arrCenter[] = $elem; } if ($bucket > 0) { $arrRight[] = $elem;} }
$countLeft = count($arrLeft); $countCenter = count($arrCenter); $countRight = count($arrRight);
return array_sum([$countLeft, $countCenter, $countRight]) / 3;}
public function someMethodWithMisleadingName( ParallelListCollection $mysteriousInput) { return $mysteriousInput ->filter(function ($elem) { return $elem > 10; }) ->partition(function ($elem) { return $elem <=> 20; }) ->map(function ($bucket) { return $bucket->count(); }) ->avg();}
public function someMethodWithMisleadingName( array $mysteriousInput) { $arr = []; foreach ($mysteriousInput as $inp) { if ($inp > 10) { $arr[] = $inp; } }
$arrLeft = $arrRight = $arrCenter = []; foreach ($arr as $elem) { $bucket = $elem <=> 20; if ($bucket < 0) { $arrLeft[] = $elem; } if ($bucket == 0) { $arrCenter[] = $elem; } if ($bucket > 0) { $arrRight[] = $elem;} }
$countLeft = count($arrLeft); $countCenter = count($arrCenter); $countRight = count($arrRight);
return array_sum([$countLeft, $countCenter, $countRight]) / 3;}
public function someMethodWithMisleadingName( ParallelListCollection $mysteriousInput) { return $mysteriousInput ->filter(function ($elem) { return $elem > 10; }) ->partition(function ($elem) { return $elem <=> 20; }) ->map(function ($bucket) { return $bucket->count(); }) ->avg();}
Fundamental concepts in functional programming
❏ Function is a first-class citizen
❏ No side effects
❏ Immutability
❏ Lambda Calculus
First-class citizen
❏ Can be stored in variable and data structures
❏ Can be passed as a parameter to procedure/functions
❏ Can be returned by procedures/functions
❏ Can be instantiated inline
❏ Has it’s own identity (name independent)
No side effects? Immutability?
:(
Lambda Calculus
ƛ(x) = z
Lambda Calculus
ƛ(x) = z❏ Higher-order functions❏ Currying
Functional vs Object oriented programming
?
PHP7 is functional
…but is dirty and salty as well
What do I miss in PHP7 that Scala luckily has?
❏ Immutability by default❏ Objects cloning❏ Options❏ Either❏ Future❏ Parallel collections❏ Tail recurrency
❏ Generic types❏ Arrow functions❏ Pattern matching / case classes
Few rules to make your code functional
Do not use
❏ reassignments❏ if❏ null❏ for❏ foreach
Do not use
❏ reassignments
$bigHouse = new Building(5);$smallerHouse = $bigHouse->setFloors(2);
echo $bigHouse->getFloors() . PHP_EOL; echo $smallerHouse->getFloors() . PHP_EOLl;
$bigHouse = new Building(5);$smallerHouse = $bigHouse->setFloors(2);
echo $bigHouse->getFloors() . PHP_EOL; //2echo $smallerHouse->getFloors() . PHP_EOLl; //2
class Building{ protected $floors;
public function __construct(int $floors) { $this->setFloors($floors); }
public function getFloors() : int { return $this->floors; }
public function setFloors(int $floors) : Building { $this->floors = $floors; return $this; }}
class Building{ protected $floors;
public function __construct(int $floors) { $this->floors = $floors; }
public function getFloors() : int { return $this->floors; }
private function setFloors(int $floors) : Building { $this->floors = $floors; return $this; }
public function withFloors(int $floors) : Building { return (clone($this))->setFloors($floors); }}
$bigHouse = new Building(5);$smallerHouse = $bigHouse->withFloors(2);
echo $bigHouse->getFloors() . PHP_EOL; //5echo $smallerHouse->getFloors() . PHP_EOLl; //2
trait Copy{ public function copy($field, $value) { $clone = clone $this; $clone->$field = $value; return $clone; }}
use PhpSlang\Util\Copy;
class Building{ use Copy;
protected $floors;
public function __construct(int $floors) { $this->floors = $floors; }
public function getFloors() : int { return $this->floors; }
public function withFloors(int $floors) : Building { return $this->copy('floors', $floors); }}
Few rules to make your code functional
Do not use
:) reassignments❏ if❏ null❏ for❏ foreach
https://github.com/php-slang/php-slang
Do not use
:) reassignments❏ if❏ null❏ for❏ foreach
?
Do not use
:) reassignments❏ if❏ null❏ for❏ foreach
Option
OptionMonad which may contain something or nothing
What is a monad?Option
Fishy Monad Tutorial
http://maciejpirog.github.io/fishy/ (cc-by-sa)
Fishy Monad Tutorial
http://maciejpirog.github.io/fishy/ (cc-by-sa)
Fishy Monad Tutorial
http://maciejpirog.github.io/fishy/ (cc-by-sa)
Fishy Monad Tutorial
http://maciejpirog.github.io/fishy/ (cc-by-sa)
https://github.com/php-slang/php-slang
# composer require php-slang/php-slang
Option
Option
NoneSome
Option
Option
NoneSomemap(Closure $expression)getOrElse($default)
map(Closure $expression)getOrElse($default)
Option
Option
NoneSomemap(Closure $expression)getOrElse($default)
map(Closure $expression)getOrElse($default)
Some($expression($this->content)
$this->content
Option
Option
NoneSomemap(Closure $expression)getOrElse($default)
map(Closure $expression)getOrElse($default)
None
$default
class UserRepository extends EntityRepository{ public function findByEmail(string $email) : User { $user = $this->findOneByMail(['email' => $email]);
if (!$user instanceof User) { throw new NotFoundException("oh my"); }
return $user; }}
public function findUserAction(string $email) : Response try { $user = $this ->userRepository ->findByEmail($email); return new Response($user); } catch (NotFoundException $exception) { return new Response([], Response::HTTP_NOT_FOUND); }}
class UserRepository extends EntityRepository{ public function findByEmail(string $email) : Option { return Option::of($this>findOneByMail(['email' => $email])); }}
public function findUserAction(string $email) : Response return $this ->userRepository ->findByEmail($email)); ->map(function (User $user) { return new Response($user); }) ->getOrElse(new Response('', Response::HTTP_NOT_FOUND));}
class UserRepository extends EntityRepository{ public function findByEmail(string $email) : User { $user = $this->findOneByMail(['email' => $email]);
if (!$user instanceof User) { throw new NotFoundException("oh my"); }
return $user; }}
public function findUserAction(string $email) : Response try { $user = $this ->userRepository ->findByEmail($email); return new Response($user); } catch (NotFoundException $exception) { return new Response([], Response::HTTP_NOT_FOUND); }}
class UserRepository extends EntityRepository{ public function findByEmail(string $email) : Option { return Option::of( $this>findOneByMail(['email' => $email])); }}
public function findUserAction(string $email) : Response return $this ->userRepository ->findByEmail($email)); ->map(function (User $user) { return new Response($user); }) ->getOrElse( new Response('', Response::HTTP_NOT_FOUND));}
OptionHow about nesting
public function displayNameForUser(string $email) : string{ $this ->userRepository ->findByEmail($email) ->get() ->getFirstName();}
public function displayNameForUser(string $email) : string{ $this ->userRepository ->findByEmail($email) ->map(function (User $user) { return $user->firstName; }) ->getOrElse('oh my');}
public function displayNameForUser(string $email) : ???{ $this ->userRepository ->findByEmail($email) ->map(function (User $user) { return $user->getFirstName(); });}
public function displayNameForUser(string $email) : ???{ $this ->userRepository ->findByEmail($email) ->map(function (User $user) { return $user->getFirstName(); });}
?
public function displayNameForUser(string $email) : ???{ $this ->userRepository ->findByEmail($email) ->map(function (User $user) { return $user->getFirstName(); });}
Option<Option<String>>
public function displayNameForUser(string $email) : Option{ $this ->userRepository ->findByEmail($email) ->flatMap(function (User $user) { return $user->getFirstName(); });}
public function displayNameForUser(string $email) : string{ $this ->userRepository ->findByEmail($email) ->flatMap(function (User $user) { return $user->getFirstName(); }) ->getOrElse($email);}
public function displayNameForUser(string $email) : string{ $this ->userRepository ->findByEmail($email) ->flatMap(function (User $user) { return $user->getFirstName(); }) ->getOrCall(function () use ($email) { $this->getAlternative($email); });}
public function displayNameForUser(string $email) : string{ $this ->userRepository ->findByEmail($email) ->flatMap(function (User $user) { return $user->getFirstName(); }) ->getOrCall($this->getAlternative($email));}
public function displayNameForUser(string $email) : string{ $this ->userRepository ->findByEmail($email) ->flatMap(function (User $user) { return $user->getFirstName(); }) ->getOrCall($this->getAlternative($email));}
public function getAlternative(string $email) : \Closure{ return function () use (string $email) : string { return $this->doSomethingElseWith($email); };}
Few rules to make your code functional
Do not use
:) reassignments:) if:) null❏ for❏ foreach
Shortened notation for anonymous functions
public function displayNameForUser(string $email) : string{ return $this ->userRepository ->findByEmail($email) ->flatMap(function (User $user) { return $user->getFirstName(); }) ->getOrCall($this->getAlternative($email));}
public function getAlternative(string $email) : \Closure{ return function () use (string $email) : string { return $this->doSomethingElseWith($email); };}
public function displayNameForUser(string $email) : string{ $this ->userRepository ->findByEmail($email) ->flatMap((User $user) => $user->getFirstName()) ->getOrCall(() => $this->doSomethingElseWith($email))} :(
Generic types
public function maybeSomething(string $email) : Option{ ...}
public function maybeSomething(string $email) : Option<string>{ ...}
public function maybeSomething(string $email) : Option<string>{ ...}
❏ Version: 0.4.0❏ Date: 2016-01-06❏ Author: Ben Scholzen 'DASPRiD' [email protected], Rasmus Schultz [email protected]❏ Status: Draft❏ First Published at: http://wiki.php.net/rfc/generics
:(
/*** @return Option<string>*/public function maybeSomething(string $email) : Option{ ...}
https://github.com/phpDocumentor/fig-standards/blob/master/proposed/phpdoc.md
:(
What do I miss in PHP7 that Scala luckily has?
:) Immutability by default:) Objects cloning:) Options❏ Either❏ Future❏ Parallel collections❏ Tail recurrency
:( Generic types:( Arrow functions❏ Pattern matching / case classes
Either
Either
Either
RightLeft
Either
Either
RightLeftleft(Closure $expr): Eitherright(Closure $expr): Eitherget()
left(Closure $expr): Eitherright(Closure $expr): Eitherget()
public function findUserAction(string $email) : Response try { $user = $this ->userRepository ->findByEmail($email); return new Response($user); } catch (NotFoundException $exception) { return new Response([], Response::HTTP_NOT_FOUND); }}
public function findUserAction(string $email) : Response try { $user = $this ->userRepository ->findByEmail($email); return new Response($user); } catch (NotFoundException $exception) { return new Response([], Response::HTTP_NOT_FOUND); } catch (ExternalServiceResponseException $exception) { return new Response([], Response::HTTP_FAILED_DEPENDENCY); } catch (IncorrectEmailException $exception) { return new Response([], Response::HTTP_BAD_REQUEST); } catch (UserNotAllowedException $exception) { return new Response([], Response::HTTP_FORBIDDEN); }}
“Co jest piękniejszego niż rdest? No chyba tylko bylina rdestu, bo rzadziej występuje.”Ohanhutep
interface ServiceError {}
class NotFound implements ServiceError {}class ServiceNotWorking implements ServiceError {}class Param2IsPoorlyFormatted implements ServiceError {}
public function getSomethingNontrivial(string $param1, string $param2, string $param3) : Either{ ...}
Either<ServiceError, User>
public function exampleAction(string $param1, string $param2, string $param3) : Response {
return $this ->userService ->getSomethingNontrivial($param1, $param2, $param3) ->left(function (ServiceError $someKindOfFailure) : Response { new Case(ServiceNotWorking::class, new Response('', Response::HTTP_FAILED_DEPENDENCY)), new Case(Param2IsPoorlyFormatted::class, new Response('', Response::HTTP_BAD_REQUEST)), new Case(NotFound()::class, new Response([], Response::HTTP_NOT_FOUND)); }) ->right(function (User $nonTrivialAllRight) : Response { return new Response($nonTrivialAllRight, Response::HTTP_OK); }) ->get();}
public function getSomethingNontrivial( string $param1, string $param2, string $param3) : Either{ return $this ->translateParam2($param2) ->map(function ($param2Translated) { return new Right($this->getUserBy($param2Translated)); }) ->getOrElse(new Left(new Param2IsPoorlyFormatted()));}
public function getSomethingNontrivial(string $param1, string $param2, string $param3) : Either{ return $this ->translateParam2($param2) ->map($this->handleWithTranslatedParam($param1, $param3)) ->getOrElse(new Left(new Param2IsPoorlyFormatted()));}
public function handleWithTranslatedParam(string $param1, string $param3) : \Clojure{ return function (Param2Translated $param2Translated) use ($param1, $param3) : Either { return $this ->someOtherMagic($param2Translated, $param1, $param3) ->map(function (User $magicResult) use ($param1, $param3) : Either { return new Right($magicResult); }) ->getOrElse(new Left(new ServiceNotWorking())); };}
What do I miss in PHP7 that Scala luckily has?
:) Immutability by default:) Objects cloning:) Options❏ Either❏ Future❏ Parallel collections❏ Tail recurrency
:( Generic types:( Arrow functions❏ Pattern matching / case classes
Pattern Matching
public function exampleAction(string $param1, string $param2, string $param3) : Response{ return $this ->userService ->getSomethingNontrivial($param1, $param2, $param3) ->left(function (ServiceError $someKindOfFailure) : Response { return (Match::of($someKindOfFailure))->match( new Case(ServiceNotWorking::class, new Response('', Response::HTTP_FAILED_DEPENDENCY)), new Case(Param2IsPoorlyFormatted::class, new Response('', Response::HTTP_BAD_REQUEST)), new Case(NotFound::class, new Response([], Response::HTTP_NOT_FOUND)); }) ->right(function (User $nonTrivialAllRight) : Response { return new Response($nonTrivialAllRight, Response::HTTP_OK); }) ->get();}
def update(id: String): Action[JsValue] = Action.async(parse.json) { request => user.update(id, userConverterFactory.of(request.body).toInput)
.map {case Right(user) => Ok(user)case Left(UserService.UserNotFound) => NotFoundcase Left(UserService.VersioningMissmatch) => NotAcceptablecase Left(UserService.NoModificationsAllowed) => Lockedcase Left(UserService.InvalidPayload) => BadRequest
}}
What do I miss in PHP7 that Scala luckily has?
:) Immutability by default:) Objects cloning:) Options:) Either❏ Future❏ Parallel collections❏ Tail recurrency
:( Generic types:( Arrow functions:)/:( Pattern matching / case classes
Parallel collections
public function multiplyBy( array $input, float $multiplication): array{ $output = [];
foreach($input as $number) { $output[] = $number * $multiplication; }
return $output;}
use PhpSlang\Collection\ListCollection;...public function beautifulMultiplyBy( array $input, float $multiplication) : ListCollection{ return (new ListCollection($input)) ->map(function ($number) use ($multiplication) { return $number * $multiplication; });}
public function multiplyOddsBy( array $input, float $multiplication): array{ $output = [];
foreach ($input as $number) { if ($number % 2 !== 0) { $output[] = $number * $multiplication; } }
return $output;}
public function beautifulMultiplyOddsBy( array $input, float $multiplication) : ListCollection{ return (new ListCollection($input)) ->filter(function ($number) { return $number % 2 !== 0; }) ->map(function ($number) use ($multiplication) { return $number * $multiplication; });}
public function accumulatedText(array $words) : string { $text = '';
foreach ($words as $word) { $text .= $word . ' '; }
return $text;}
public function accumulatedText(array $words) : string{ return (new ListCollection($words)) ->fold('', function (string $acumulator, string $word) { return $acumulator . $word . ' '; });}
(new ListCollection([1,2,3,4]))->tail(); //ArrayCollection([2,3,4])
Few rules to make your code functional
Do not use
:) reassignments:) if:) null:) for:) foreach
Parallelism vs Concurrency
Future
public function nonBlockingGet(string $id): Future{ ...}
public function exampleAction(string $id1) : Response{ return $this ->nonBlockingService ->nonBlockingGet($id) ->map(function (NonBlockingGetResult $output) { return new Response($output); }) ->await();}
public function nonBlockingGet(string $id): Future{ ...}
public function exampleAction(string $id1) : Response{ return $this ->nonBlockingService ->nonBlockingGet($id) ->map(function (NonBlockingGetResult $output) { return new Response($output); }) ->await();}
Future<NonBlockingGetResult>
Jak powinno to wyglądać?
public function nonBlockingGet(string $id): Future{ ...}
public function exampleAction(string $id1) : Response{ return $this ->nonBlockingService ->nonBlockingGet($id) ->map(function (NonBlockingGetResult $output) { return new Response($output); }) ->await();}
Future<NonBlockingGetResult>
Jak powinno to wyglądać?
Future<Response>
public function nonBlockingGet(string $id): Future{ ...}
public function exampleAction(string $id1) : Response{ return $this ->nonBlockingService ->nonBlockingGet($id) ->map(function (NonBlockingGetResult $output) { return new Response($output); }) ->await();}
Future<NonBlockingGetResult>
Jak powinno to wyglądać?
Future<Response>
Response
public function nonBlockingGet(string $id): Future{ ...}
public function exampleAction(string $id1, string $id2, string $id3) : Response{ return Future::all([ $this->nonBlockingService1->nonBlockingGet($id1), $this->nonBlockingService2->nonBlockingGet($id2), $this->nonBlockingService3->nonBlockingGet($id3), ]) ->map(function ($output) { return new Response($output); }) ->await();}
Jak powinno to wyglądać?
public function nonBlockingGet(string $id): Future{ ...}
public function exampleAction(string $id1, string $id2, string $id3) : Response{ return Future::all([ $this->nonBlockingService1->nonBlockingGet($id1), $this->nonBlockingService2->nonBlockingGet($id2), $this->nonBlockingService3->nonBlockingGet($id3), ]) ->map(function ($output) { return new Response($output); }) ->await();}
Jak powinno to wyglądać?
Future & Parallel collections
use PhpSlang\Collection\ListCollection;...public function beautifulMultiplyBy( array $input, float $multiplication) : ListCollection{ return (new ListCollection($input)) ->map(function ($number) use ($multiplication) { return $number * $multiplication; });}
use PhpSlang\Collection\ParallelListCollection;...public function beautifulMultiplyBy( array $input, float $multiplication) : ParallelListCollection{ return (new ParallelListCollection($input)) ->map(function ($number) use ($multiplication) { return $number * $multiplication; });}
class ParallelListCollection extends ListCollection{ public function map(Closure $func) { return Future::all( (new ArrayCollection($this->elements)) ->map(function ($element) use ($func) { return new Future(function () use ($func, $element) { return $func($element); }); }) ->toArray()) ->await(); }}
class ParallelListCollection extends ListCollection{ public function map(\Closure $func) { return Future::all( (new ArrayCollection($this->elements)) ->map(function ($element) use ($func) { return new Future(function () use ($func, $element) { return $func($element); }); }) ->toArray()) ->await(); }}
ArrayCollection<Future<mixed>>
Future<ArrayCollection<mixed>>
ArrayCollection<mixed>
use PhpSlang\Collection\ParallelListCollection;...public function asyncChainedComputationExample(array $input) : ParallelListCollection{ return (new ParallelListCollection($input))
->map($this->transformationOne())
->map($this->transformationTwo())
->map($this->transformationThree();}
use PhpSlang\Collection\ParallelListCollection;...public function asyncChainedComputationExample(array $input) : ParallelListCollection{ return (new ParallelListCollection($input))
->map($this->transformationOne())
->map($this->transformationTwo())
->map($this->transformationThree();}
use PhpSlang\Collection\ParallelListCollection;...public function asyncChainedComputationExample(array $input) : ParallelListCollection{ return (new ParallelListCollection($input)) ->map(function ($number) { return Option::of($number) ->map($this->transformationOne())
->map($this->transformationTwo())
->map($this->transformationThree()
->get(); });}
use PhpSlang\Collection\ParallelListCollection;…public function asyncChainedComputationExample(array $input) : ParallelListCollection{ return (new ParallelListCollection($input)) ->map(function ($number) { return Option::of($number) ->map($this->transformationOne())
->map($this->transformationTwo())
->map($this->transformationThree()
->get(); });}
What do I miss in PHP7 that Scala luckily has?
:) Immutability by default:) Objects cloning:) Options:) Either:)/:( Future:) Parallel collections❏ Tail recurrency
:( Generic types:( Arrow functions:)/:( Pattern matching / case classes
Tail recurrency
def fibonacci(index : Int) : Int = index match { case 0 | 1 => index case _ => fibonacci(index - 1 ) + fibonacci(index - 2)}
function fibonacci(int $index) : int{ return in_array($index, [0, 1]) ? $index : fibonacci($index - 1) + fibonacci($index - 2);}
def fibonacci(index : Int) : Int = index match { case 0 | 1 => index case _ => fibonacci(index - 1 ) + fibonacci(index - 2)}
function fibonacci(int $index) : int{ return in_array($index, [0, 1]) ? $index : fibonacci($index - 1) + fibonacci($index - 2);}
echo fibonacci(123123123123);
Fatal error: Maximum function nesting level of '...' reached, aborting!
ini_set('xdebug.max_nesting_level', 9999999);
?
def fibonacci(index: Int): Int = { var a = 0 var b = 1 var i = 0
while (i < index) { val c = a + b a = b b = c i = i + 1 } return a}
function fibonacci(int $index) : int{ $a = 0; $b = 1; $i = 0;
while ($i < $index) { $c = $a + $b; $a = $b; $b = $c; $i += 1; } return $a;}
def recursiveFibonacci(n: Int, a:Int, b:Int): Int =n match { case 0 => a case _ => recursiveFibonacci( n-1, b, a+b ) }
def fibonacci( n : Int) : Int = recursiveFibonacci( n, 0, 1)
function recursiveFibonacci(int $n, int $a, int $b) { return ($n == 0) ? $a : recursiveFibonacci($n - 1, $b, $a + $b);}
function fibonacci(int $n) : int{ return recursiveFibonacci($n, 0, 1);}
def fibonacci(index : Int) : Int = index match { case 0 | 1 => index case _ => fibonacci(index - 1 ) + fibonacci(index - 2)}
function fibonacci(int $index) : int{ return in_array($index, [0, 1]) ? $index : fibonacci($index - 1) + fibonacci($index - 2);}
def recursiveFibonacci(n: Int, a:Int, b:Int): Int =n match { case 0 => a case _ => recursiveFibonacci( n-1, b, a+b ) }
def fibonacci( n : Int) : Int = recursiveFibonacci( n, 0, 1)
function recursiveFibonacci(int $n, int $a, int $b) { return ($n == 0) ? $a : recursiveFibonacci($n - 1, $b, $a + $b);}
function fibonacci(int $n) : int{ return recursiveFibonacci($n, 0, 1);} :(
Tail recurrencyTrampolines
Recurrency
Recurrency Trampoline
<?php
namespace PhpSlang\Util\Trampoline;...class Trampoline{ /** * @var TrampolineResult */ var $expression;
public function __construct(Closure $expression) { $this->expression; } public function run() { $result = new Bounce(function () { return ($this->expression)(); }); while ($result instanceof Bounce) { $result = $result->run(); } return $result->run()->get(); }}
interface TrampolineResult{ public function run() : TrampolineResult;
public function get();}
class Bounce implements TrampolineResult {...}
class Done implements TrampolineResult {...}
function recursiveFibonacci(int $n, int $a, int $b) { return ($n == 0) ? $a : recursiveFibonacci($n - 1, $b, $a + $b);}
function fibonacci($n){ return recursiveFibonacci($n, 0, 1);}
echo fibonacci(8);
function recursiveFibonacci(int $n, int $a, int $b) { return ($n == 0) ? new Done($a) : new Bounce(function () use ($n, $b, $a) { return recursiveFibonacci($n - 1, $b, $a + $b); });}
function fibonacci($n){ return (new Trampoline(function () use ($n) { return recursiveFibonacci($n, 0, 1); }))->run();}
echo fibonacci(8);
What do I miss in PHP7 that Scala luckily has?
:) Immutability by default:) Objects cloning:) Options:) Either:)/:( Future:) Parallel collections:) Tail recurrency
:( Generic types:( Arrow functions:)/:( Pattern matching / case classes
Conclusions
● Don’t be afraid of monads● Don’t set traps for your team
● Learn Haskell, Clojure, Scala, F#, JavaScript -> TypeScript
Witek Adamus
xsolve.pl/nobodyexpects