An Elephant of a Different Colour: Hack

An Elephant of a Different Colour: Hack

Reduce your Server Load, Reuse your Code and
Recycle your PHP Skills with HHVM & Hack
Image Copyright Keith Evans. This work is licensed under the Creative Commons Attribution-Share Alike 2.0 Generic Licence. To view a copy of this licence,
visit http://creativecommons.org/licenses/by-sa/2.0/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.

Just in case you’re not up to
speed on this HHVM stuff…

© Some rights reserved by Dave Hamster

© Some rights reserved by Andy Barnes

© Some rights reserved by Casey Fleser

Hack

Collection
Lambd
Type
Async
XHP
a
s

XHP

<?hh
require_once('lib/init.php');
$class = "greeting";
$subject = "Toronto & area";
$body = $hello {ucwords($subject)};
echo <x:doctype>
<html>
<head><title>Hello XHP</title></head>
<body>{$body}</body>
</html>
<!DOCTYPE html>
</x:doctype>;
<html>

<head><title>Hello XHP</title></head>
<body>
$hello Toronto & Area
</body>
</html>

XHP

<?hh
require_once('lib/init.php');
$list = <ul />;
for ($i = 0; $i < 7; $i += 1) {
$list->appendChild(<li>{date('l', time() + $i * 86400)}</li>);
}
<ul>
echo $list;
XHP emits HTML without
the whitespace and
formatting. I’ve added it
for readability.

<li>Monday</li>
<li>Tuesday</li>
<li>Wednesday</li>
<li>Thursday</li>
<li>Friday</li>
<li>Saturday</li>
<li>Sunday</li>
</ul>

XHP
•

Available for Zend PHP too!

•

See https://github.com/facebook/xhp

•

Can use HTML() to emit unescaped HTML but
don’t.

Collections
Vecto
r
0 => ‘Apples’,
1 => ‘Bananas’,
2 => ‘Oranges’

Ma
p
[Red] => ‘Apples’,
[Yellow] => ‘Bananas’,
[Orange] => ‘Oranges’

Se
t

Pai
r
0 => ‘Apples’,
1 => ‘Bananas’

‘Apples’,
‘Bananas’
‘Oranges’

Vectors
<?hh
$v = Vector { "zero", "one" };
$v[] = 2;
$v->add($v->count());
$v->removeKey(0);
print_r($v);

[0] => "zero"
[1] => “one”
[0] => "zero"
[1] => "one"
[2] => 2
[0] => "zero"
[1] => "one"
[2] => 2
[3] => 3
[0] => “one"
[1] => 2
[2] => 3

Old School Arrays

<?php
$v = array("zero", “one”);

[0] => “zero"
[1] => “one"

$v[] = 2;

[0] => "zero"
[1] => "one"
[2] => 2

array_push($v, count($v));
unset($v[0]);
print_r($v);
Can you spot the difference between
the Hack and PHP results?

[0] => "zero"
[1] => "one"
[2] => 2
[3] => 3
[1] => "one"
[2] => 2
[3] => 3

Vectors
•

Always 0 .. (count -1)

•

Values are not hashed / indexed
•

•

Use Sets for this

Can use [] to append, but not unset() to remove

Pair
<?hh
require_once('../lib/init.php');
$dynamicDuo = Pair {'Batman', 'Robin'};
$p = Pair {$dynamicDuo, The dynamic Duo};
print_r($p);

Pair Object
(
[0] => Pair Object
(
[0] => Batman
[1] => Robin
)
[1] => xhp_p Object
(
[tagName:protected] => p
[attributes:xhp_x__composable_element:private] => Array
()
[children:xhp_x__composable_element:private] => Array
(
[0] => The dynamic Duo
)
[source] => /home/vic/prog/presentation/collections/pair.php:4
)
)

Pair
•

Pairs must contain two items of any type

•

Pairs are always immutable

•

Items are accessed with [0] and [1]

Map
<?hh
$map = Map {
'CA' => 'Canada',
'US' => 'United States'
};
Map Object
$map->add(Pair {'MX', 'Mexico'}); (
$map['NI'] = 'Nicaragua';
[CA] => Canada
print_r($map);

)

[US] => United States
[MX] => Mexico
[NI] => Nicaragua

Map
•

Maps contain key / value Pairs

•

Keys can only be integers or strings

•

Values can be of any type

•

Order is preserved

Set

<?hh
$s = Set {'US', 'CA'};
$s->add('MX');
$s[] = 'NI';
$s[] = ($s->contains('CA') ? 'Has' : 'Lacks') . ' Canada';
print_r($s);
•

Can only contain integers or
strings

•

Unordered

HHSet Object
(
US
CA
MX
NI
Has Canada
)

Types
<?hh
function add(int $a, int $b): int {
return $a + $b;
}
var_dump(add(1, 2));
var_dump(add(1.5, 2));
int(3)
HipHop Fatal error: Argument 1 passed to add() must be an
instance of int, double given in
/home/vic/prog/presentation/type.php on line 4

Types
<?hh
function add(
shape('x' => int, 'y' => int) $p1,
shape('x' => int, 'y' => int) $p2
): shape('x' => int, 'y' => int) {
return shape(‘x' => $p1['x'] + $p2['x'], 'y' => $p1['y'] + $p2[‘y']);
}
var_dump(add(['x' => 3, 'y' => 4], ['x' => 5, 'y' => 25]));

array(2) {
["x"]=>int(8)
["y"]=>int(29)
}

Types

<?hh
type Coord = shape('x' => int, 'y' => int);
function add(Coord $p1, Coord $p2): Coord {
return ['x' => $p1['x'] + $p2['x'], 'y' => $p1['y'] + $p2['y']];
}
var_dump(add(['x' => 3, 'y' => 4, 'z' => 1], ['x' => 5, 'y' =>
25]));
var_dump(add(['x' => 3, 'z' => 4], ['x' => 5, 'y' => 25]));

array(2) {[“x”]=>int(8), [“y"]=>int(29)}
HipHop Notice: Undefined index: y in
/home/vic/prog/presentation/typedef.php on line 4
array(2) {[“x”]=>int(8), ["y"]=>int(25)}

Generics

<?hh
class Accumulator<T> {
function __construct(private T $value) {}
function add(T $value) { $this->value += $value; }
function get():T { return $this->value; }
}
$accumulateInts = new Accumulator<int>(5);
$accumulateInts->add(4);
var_dump($accumulateInts->get());
$accumulateFloats = new Accumulator<float>(0.7);
$accumulateFloats->add(1.6);
var_dump($accumulateFloats->get());
$accumulate = new Accumulator([5]);
$accumulate->add([4,9]);
var_dump($accumulate->get());

int(9)

float(2.3)
array(2) {
[0]=>int(5)
[1]=>int(9)
}

Generics

<?hh
class Accumulator<T> {
function __construct(private T $value) {}
function add(T $value) { $this->value += $value; }
function get():T { return $this->value; }
}
$accumulateInts = new Accumulator<int>(5);
$accumulateInts->add(4);
$accumulateInts->add(4.4);
var_dump($accumulateInts->get());
float(13.4
)

!

Nullable Types
<?hh
function printNum(?int $num) {
echo "num is ";
echo is_null($num) ? "null" : $num;
echo "n";
num is 1
}
num is null
printNum(1);
HipHop Warning: Argument 1 to
printNum(null);
printNum() must be of type ?int,
printNum("Five");
string given in
/home/vic/prog/presentation/nullabl
e.php on line 6
num is Five

Types
<?hh
class MyClass<T as SomeInterface> {
function __construct(private T $v) {}
}
newtype Secret as BaseClass =
MyClass;

Lambda

<?php
$countries = [
'US' => 'United States',
'CA' => 'Canada',
'MX' => 'Mexico',
];
uasort($countries, function ($a, $b) {
return $a > $b;
array(3) {
});
["CA"]=>
string(6) "Canada"
var_dump($countries);

}

["MX"]=>
string(6) "Mexico"
["US"]=>
string(13) "United States"

Lambda

<?hh
$countries = [
'US' => 'United States',
'CA' => 'Canada',
'MX' => 'Mexico',
];
uasort($countries, ($a, $b) ==> $a >
$b);
array(3) {
var_dump($countries);

}

["CA"]=>
string(6) "Canada"
["MX"]=>
string(6) "Mexico"
["US"]=>
string(13) "United States"

Lambda
<?hh
$add = ($a, $b) ==> $a + $b;
function curry($callable, $value) {
return $v ==> $callable($value, $v);
}
$addFour = curry($add, 4);
var_dump($addFour(5));

int(9)

User Attributes
Array
(
[MyAnnotation] => Array
(
[0] => Unicorn
[1] => 42
)
$rc = new ReflectionFunction('bar');
print_r($rc->getAttributes());
)
<?hh
<< MyAnnotation('Unicorn',
42) >>
function bar() {
}

User Attributes
•

You can add attributes / annotations to classes,
methods, functions and arguments.

•

You can specify more than one set of user
attributes:
<< Foo(1), Bar(2) >>

•

You can’t use constants or variables in attributes

Async
•

I lied; hhvm’s async is more c# than node.

•

Library functions like evhttp_async_get() don’t
return Awaitable’s
•

•

So they don’t seem to play well together

PocketRent/beatbox uses async, but I don’t grock it

class Foo{}

Async

class Bar {
public function getFoo(): Foo {
return new Foo();
}
}

This is the example
Facebook provided
on GitHub for async.

async function gen_foo(int $a): Awaitable<?Foo> {
if ($a === 0) {
return null;
}
$bar = await gen_bar($a);
if ($bar !== null) {
return $bar->getFoo();
}
}

return null;

async function gen_bar(int $a): Awaitable<?Bar> {
if ($a === 0) {
return null;
}
}

return new Bar();

gen_foo(4);

More
•

See hhvm.com

•

The debugger is command line, and very good:
hhvm -m debug

•

Sara Golemon is giving a talk tomorrow night about HHVM and
hack, and it will be live streamed:
http://www.meetup.com/sf-php/events/159404382/

•

Framework for Hack:
https://wiki.pocketrent.com/beatbox/start

•

I promise to blog about Hack at http://blog.vicmetcalfe.com/

An Elephant of a Different Colour: Hack

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