public function testReduce()
{
$append = function ($xs, $x) {
return array_merge($xs, [$x]);
};
$this->assertEquals(Maybe::empty()->reduce($append, []), [], 'Nothing reduction.');
$this->assertEquals(Maybe::of(2)->reduce($append, []), [2], 'Just reduction.');
}
public function testMap()
{
$add2 = function ($x) {
return $x + 2;
};
$this->assertEquals(Maybe::empty()->map($add2)->fork(-1), -1, 'Nothing map.');
$this->assertEquals(Maybe::of(2)->map($add2)->fork(-1), 4, 'Just map.');
}
public function testChain()
{
$safeHalf = function ($x) {
return $x % 2 == 0 ? Maybe::of($x / 2) : Maybe::empty();
};
$this->assertEquals($safeHalf(16)->chain($safeHalf)->fork(null), 4, 'Just chains.');
$this->assertEquals($safeHalf(5)->chain($safeHalf)->fork(null), null, 'Nothing chains.');
}
public function testConcat()
{
$maybes = [Maybe::empty(), Maybe::of(2), Maybe::empty()];
$acc = array_reduce($maybes, function ($acc, $x) {
return $acc->concat($x);
}, Maybe::empty());
$this->assertEquals(2, $acc->fork(5), 'Concatenates.');
}
public function testEquals()
{
$a = Maybe::empty();
$b = Maybe::of(new Value(2));
$c = Maybe::of(new Value(3));
$d = Maybe::of(new Value(3));
$this->assertEquals($a->equals($a), true, 'Two Nothing values.');
$this->assertEquals($a->equals($b), false, 'Just and Nothing.');
$this->assertEquals($b->equals($c), false, 'Unequal values.');
$this->assertEquals($c->equals($d), true, 'Equal values.');
}
public function testAp()
{
$add = function ($x) {
return function ($y) use($x) {
return $x + $y;
};
};
$a = Maybe::of(2);
$b = Maybe::of(4);
$this->assertEquals(Maybe::of($add)->ap($a)->ap($b)->fork(null), 6, 'Applies to a Just.');
$this->assertEquals(Maybe::empty()->ap($a)->fork(-1), 2, 'Applies to a Nothing.');
}
public function testFork()
{
$this->assertEquals(Maybe::of(2)->fork(4), 2, 'Just fork.');
$this->assertEquals(Maybe::empty()->fork(4), 4, 'Nothing fork.');
}
public function testEmpty()
{
$this->assertInstanceOf('PhpFp\\Maybe\\Constructor\\Nothing', Maybe::empty(), 'The empty value is a nothing.');
}
public function testEmpty()
{
$this->assertInstanceOf('PhpFp\\Maybe\\Constructor\\Just', Maybe::of(2), 'The empty value is a nothing.');
$this->assertEquals(Maybe::of(2)->fork(-1), 2, 'Creates a Just value.');
}
/**
* Functor map, derived from chain.
* @param callable $f The mapping function.
* @return Maybe The outer structure is preserved.
*/
public function map(callable $f) : Maybe
{
return $this->chain(function ($a) use($f) {
return Maybe::of($f($a));
});
}