Add Phoenix Combinator.

Author: drupol

spec/loophp/combinator/Combinator/PhoenixSpec.php

@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace spec\loophp\combinator\Combinator;
+
+use PhpSpec\ObjectBehavior;
+
+class PhoenixSpec extends ObjectBehavior
+{
+    public function it_is_initializable()
+    {
+        $f = static function ($a) {
+            return static function ($b) use ($a) {
+                return 'f(' . $a . ')(' . $b . ')';
+            };
+        };
+
+        $g = static function ($a) {
+            return 'g(' . $a . ')';
+        };
+
+        $h = static function ($a) {
+            return 'h(' . $a . ')';
+        };
+
+        $arguments = [$f, $g, $h, 'x'];
+
+        $this->beConstructedWith(...$arguments);
+
+        $this()
+            ->shouldReturn('f(g(x))(h(x))');
+
+        $this
+            ->__invoke()
+            ->shouldReturn('f(g(x))(h(x))');
+    }
+}

src/Combinator/Phoenix.php

@@ -0,0 +1,67 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\combinator\Combinator;
+
+use loophp\combinator\Combinator;
+
+/**
+ * Class Phoenix.
+ *
+ * @psalm-template AType
+ * @psalm-template BType
+ * @psalm-template CType
+ * @psalm-template DType
+ */
+final class Phoenix extends Combinator
+{
+    /**
+     * @var callable
+     */
+    private $f;
+
+    /**
+     * @var callable
+     */
+    private $g;
+
+    /**
+     * @var callable
+     */
+    private $h;
+
+    /**
+     * @var mixed
+     */
+    private $x;
+
+    /**
+     * Psi constructor.
+     *
+     * @psalm-param callable(BType) : callable(CType) : DType $f
+     * @psalm-param callable(AType) : BType $g
+     * @psalm-param callable(AType) : CType $h
+     * @psalm-param AType $x
+     *
+     * @param callable $f
+     * @param callable $g
+     * @param callable $h
+     * @param mixed $x
+     */
+    public function __construct(callable $f, callable $g, callable $h, $x)
+    {
+        $this->f = $f;
+        $this->g = $g;
+        $this->h = $h;
+        $this->x = $x;
+    }
+
+    /**
+     * @psalm-return DType
+     */
+    public function __invoke()
+    {
+        return ($this->f)(($this->g)($this->x))(($this->h)($this->x));
+    }
+}