Method: apply (#1)

`apply` method that applies the content of Oks to a callable in a variadic fashion

spec/Result/ErrSpec.php

@@ -147,4 +147,10 @@ function it_converts_into_some_with_err()
         $option->shouldHaveType(Some::class);
         $option->unwrap()->shouldBe("error");
     }
+
+    function it_does_not_apply_args_in_an_err()
+    {
+        $this->beConstructedWith("error");
+        $this->apply(new Ok(123))->isErr()->shouldBe(true);
+    }
 }

spec/Result/OkSpec.php

@@ -4,7 +4,7 @@
 
 use Exception;
 use Prewk\Option\{Some, None};
-use Prewk\Result\Ok;
+use Prewk\Result\{Ok, Err};
 use PhpSpec\ObjectBehavior;
 use Prewk\Result\ResultException;
 
@@ -137,4 +137,35 @@ function it_converts_into_none_with_err()
 
         $option->shouldHaveType(None::class);
     }
+
+    function it_can_apply_argument_to_function()
+    {
+        $this->beConstructedWith(function($one) {
+            return $one;
+        });
+        $arg = new Ok(13);
+        $this->apply($arg)->unwrap()->shouldBe(13);
+    }
+
+    function it_can_apply_multiple_arguments_to_function()
+    {
+        $this->beConstructedWith(function($x, $y, $z) {
+            return $x + $y + $z;
+        });
+        $this->apply(new Ok(1), new Ok(2), new Ok(3))->unwrap()->shouldBe(6);
+    }
+
+    function it_returns_err_when_one_of_args_is_err()
+    {
+        $this->beConstructedWith(function($x, $y, $z) {
+            return $x + $y + $z;
+        });
+        $this->apply(new Ok(1), new Ok(2), new Err(3))->isErr()->shouldBe(true);
+    }
+
+    function it_throws_if_non_callable_value_is_applied_to_arguments()
+    {
+        $this->beConstructedWith(1);
+        $this->shouldThrow(ResultException::class)->during("apply");
+    }
 }

src/Result.php

@@ -142,4 +142,12 @@ public function expect(Exception $msg);
      * @return mixed
      */
     public function unwrapErr();
+
+    /**
+     * Applies values inside the given Results to the function in this Result.
+     *
+     * @param Result[] ...$args Results to apply the function to.
+     * @return Result
+     */
+    public function apply(Result ...$args): Result;
 }

src/Result/Err.php

@@ -200,6 +200,17 @@ public function unwrapErr()
     {
         return $this->err;
     }
+
+    /**
+     * Applies values inside the given Results to the function in this Result.
+     *
+     * @param Result[] ...$args Results to apply the function to.
+     * @return Result
+     */
+    public function apply(Result ...$args): Result
+    {
+        return $this;
+    }
 
     /**
      * Converts from Result<T, E> to Option<T>, and discarding the error, if any

src/Result/Ok.php

@@ -196,6 +196,29 @@ public function unwrapErr()
         throw new ResultException("Unwrapped with the expecation of Err, but found Ok");
     }
 
+    /**
+     * Applies values inside the given Results to the function in this Result.
+     *
+     * @param Result[] ...$args Results to apply the function to.
+     * @return Result
+     */
+    public function apply(Result ...$args): Result
+    {
+        if (!is_callable($this->value)) {
+            throw new ResultException("Tried to apply a non-callable to arguments");
+        }
+        return array_reduce($args, function(Result $final, Result $result) {
+            return $final->andThen(function(array $array) use ($result) {
+                return $result->map(function($x) use ($array) {
+                    array_push($array, $x);
+                    return $array;
+                });
+            });
+        }, new static([]))->map(function(array $argArray) {
+            return call_user_func_array($this->value, $argArray);
+        });
+    }
+
     /**
      * Converts from Result<T, E> to Option<T>, and discarding the error, if any
      *