feat: Add Blackbird combinator.

drupol · drupol · commit 6be63bc8d555 · 2021-08-03T09:15:23.000+02:00
diff --git a/spec/loophp/combinator/Combinator/BlackbirdSpec.php b/spec/loophp/combinator/Combinator/BlackbirdSpec.php
@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace spec\loophp\combinator\Combinator;
+
+use Closure;
+use PhpSpec\ObjectBehavior;
+
+class BlackbirdSpec extends ObjectBehavior
+{
+    public function it_is_initializable()
+    {
+        $a = 'array_sum';
+
+        $b = static fn (callable $c): Closure => static fn (array $v): array => array_map($c, $v);
+
+        $c = 'count';
+
+        $this::of()($a)($b)($c)([['a', 'b', 'c'], ['a', 'b']])
+            ->shouldReturn(5);
+    }
+}
diff --git a/spec/loophp/combinator/CombinatorsSpec.php b/spec/loophp/combinator/CombinatorsSpec.php
@@ -74,6 +74,43 @@ public function it_can_test_the_B_combinator()
             );
     }
 
+    public function it_can_test_the_Blackbird_combinator()
+    {
+        $a = 'array_sum';
+
+        $b = static fn (callable $c): Closure => static fn (array $v): array => array_map($c, $v);
+
+        $c = 'count';
+
+        $d = [['a', 'b', 'c'], ['a', 'b']];
+
+        $this::Blackbird()($a)($b)($c)($d)
+            ->shouldReturn(5);
+
+        // (S(K(S(KS)K)))(S(KS)K)
+        $this::Blackbird()($a)($b)($c)($d)
+            ->shouldReturn(
+                Combinators::S()(
+                    Combinators::K()
+                    (
+                        Combinators::S()
+                        (
+                            Combinators::K()(Combinators::S())
+                        )
+                        (Combinators::K())
+                    )
+                )
+                (
+                    Combinators::S()
+                    (
+                        Combinators::K()(Combinators::S())
+                    )
+                    (Combinators::K())
+                )
+                ($a)($b)($c)($d)
+            );
+    }
+
     public function it_can_test_the_C_combinator()
     {
         $f = static function ($x) {
diff --git a/src/Combinator/Blackbird.php b/src/Combinator/Blackbird.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\combinator\Combinator;
+
+use Closure;
+use loophp\combinator\Combinator;
+
+/**
+ * Class Blackbird.
+ *
+ * @template NewAType
+ * @template NewBType
+ * @template NewCType
+ * @template NewDType
+ *
+ * phpcs:disable Generic.Files.LineLength.TooLong
+ */
+final class Blackbird extends Combinator
+{
+    /**
+     * @return Closure(callable(NewCType): NewDType): Closure(callable(NewAType): callable(NewBType): NewCType): Closure(NewAType): Closure(NewBType): NewCType
+     */
+    public function __invoke(): Closure
+    {
+        return B::of()(B::of())(B::of());
+    }
+}
diff --git a/src/Combinators.php b/src/Combinators.php
@@ -7,6 +7,7 @@
 use Closure;
 use loophp\combinator\Combinator\A;
 use loophp\combinator\Combinator\B;
+use loophp\combinator\Combinator\Blackbird;
 use loophp\combinator\Combinator\C;
 use loophp\combinator\Combinator\D;
 use loophp\combinator\Combinator\E;
@@ -52,6 +53,11 @@ public static function B(): Closure
         return B::of();
     }
 
+    public static function Blackbird(): Closure
+    {
+        return Blackbird::of();
+    }
+
     public static function C(): Closure
     {
         return C::of();
diff --git a/tests/static-analysis/Blackbird.php b/tests/static-analysis/Blackbird.php
@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\combinator\Tests\StaticAnalysis;
+
+use loophp\combinator\Combinator\Blackbird;
+
+/**
+ * @param Blackbird<int, int, int, int> $combinator
+ * @param callable(int): int $f
+ * @param callable(string): Closure(string): int $g
+ * @param string $h
+ * @param string $x
+ */
+function test(Blackbird $combinator, callable $f, callable $g, int $h, int $x): int
+{
+    return $combinator->__invoke()($f)($g)($h)($x);
+}
