public function testAp()
{
$a = Writer::of(5, new Monoid([]));
$this->assertEquals(Writer::of(function ($x) {
return $x + 2;
}, new Monoid([]))->ap($a)->run()[0], 7, 'Applies a parameter.');
}
public function testTell()
{
$writer = Writer::of(2, Monoid::empty());
list($xs, $log) = $writer->chain(function ($x) use($writer) {
$log = new Monoid(['Hello, world!']);
return $writer->tell($log)->map(function ($_) use($x) {
return $x * 2;
});
})->run();
$this->assertEquals($xs, 4, 'Maps correctly.');
$this->assertEquals($log->value, ['Hello, world!'], 'Logs correctly.');
}
public function testChain()
{
$halve = function ($number) {
$log = new _(['Halving the number']);
return Writer::tell($log)->map(function () use($number) {
return $number / 2;
});
};
list($xs, $log) = $halve(16)->chain($halve)->run();
$this->assertEquals($xs, 4, 'Chains the value.');
$this->assertEquals($log->value, ['Halving the number', 'Halving the number'], 'Chains the log.');
}
public function testApplicativeConstructor()
{
$this->assertEquals(Writer::of(2, Monoid::empty())->run()[0], 2, 'Constructs an applicative.');
}